K-Member / Rack & Pinion Steering Suggestions

[72bluNblu]

Maybe I misinterpreted DionR. I was thinking he wanted the newer spindle because of brake availability, possibly what is "used" out there. Just my guess /assumption.

72 bluNblu is correct.....but the point (from the customers / builders) of all rack and pinion / coil over conversions are.
1) room not only for headers clearance but larger engine applications
2) weight savings
3) compact modern rack and pinion steering

1) Yup, makes sense. Some engine swaps that aren't well supported don't have good header options. I would argue that there are a lot of swaps that are pretty well supported, but, that mostly boils down to anything *I* want to run has a least a couple options. So I get that.

2) We've been through this. It's not that much weight savings

• ~50 lbs lighter than the OE K member and suspension with factory power steering (vs HDK w/ power rack)
• ~35 lbs lighter than an OE K member and suspension using a Borgeson power steering box (vs a power rack)
• ~31 lbs lighter than an OE K and suspension w/manual steering (vs a manual rack)

Those are vs. stock mopar parts too, and using 1" torsion bars for that weight. If you install tubular LCA's, aluminum strut rods etc there is additional weight savings to be had. The QA1 LCA's save about 8 lbs. The Qa1 K saves about the same. Just that knocks 16 lbs off.

And yes, if you go OE K and OE power steering to an HDJ with a manual rack the savings is about 70 lbs, but that's not a like-to-like comparison. The OE power steering is a boat anchor, even going from OE power steering to OE manual steering saves 40lbs. If you compare the OE K and manual steering to an HDK and power rack it's only a 9 lb savings. Again, with factory parts, this means you can have a factory K and manual steering weigh less with the right aftermarket parts. But that's comparing manual to power again.

A more detailed break down is here Anybody running the RMS AlterKation? Was it really worth the cost?

3) Gets you a rack and pinion. Can't argue that much, if you really want a rack and pinion that's the best way to do it. I personally don't understand the need, I think a lot of people are comparing worn out steering/suspension parts to a new rack. But it's a good reason if that's what you want.

geometry rarely comes up, it is more about the ease of achieving increased caster (6 degrees positive, piece of cake), the ability to add crazy camber (auto X) and of course hub to hub width. HDK's exclusive, time proven (now 25 years / zero failures) upper shock mount / chromoly support allows for not only a longer shock / spring combination, but a narrow hub to hub. Adjustable ends on all control arms make it possible to not only fit off the shelf rims, but specialty wheels a customer might already own.

As far as turning radius....HDK uses out of the box spindles, so turning radius is not compromised as with those that modify / lengthen the steering arm.

I own both OEM (with HDK tubular uppers) and HDK personal Dusters and drive them back to back. Both have power steering, sway bars and fresh components with the same alignment specs (6 degrees positive caster / .25 degree negative camber on pass side / .50 negative camber on the driver side / 1/8" total toe. All specs with added 3/4" front ride height . While I have no problem with torsion bars vs coil springs except they are in the way, I still like the precise steering of the rack and pinion, not to mention additional benefits listed above.

Sure, but I can get ALL of those alignment numbers with just a set of SPC UCA's, and everything else bone stock factory. Let alone all of the other stuff I usually upgrade. Now with a 3/4" ride height increase you probably do have a geometry improvement vs torsion bars, because you have more control over spindle heights and stuff. The torsion bar system does not like added ride height, and the best geometry occurs with some modest lowering.

I just hate it when people say stuff like they "need" a coil-over conversion to improve handling. No, you don't. And adding a rack and pinion doesn't make you faster. 10 years ago there wasn't nearly as much aftermarket support for the torsion bar system, now you can achieve a lot of the same improvements with off the shelf aftermarket parts.

And again, thanks Denny. For supporting the community and providing a great suspension set up. I mean, if you want a rack and pinion it is the way to do it, and while I don't want/need one other people do, and that's fine. I just want people to be real about what the advantages and disadvantages really are.

Thanks for the education Guys! Very informative!

Hemi-Denny nailed it for me. 120+ pounds of weight savings, greater accessibility in the engine compartment and very easy to assemble/disassemble . Way better steering feel. After speaking with Bill Reilly, I'm satisfied the geometry is great for my needs. (again not suggesting it can't be done with the stock setup). I can't speak for anyone else but , trust me, I didn't spend all this money converting because it "looked pretty" . BTW I don't have any issue with steering shaft angle. See below as the shaft uses a universal provided in the kit. No binding and works great.

120 lbs where? No sir. Weight savings of actual parts are posted above.

 

[DionR]

And again, thanks Denny. For supporting the community and providing a great suspension set up. I mean, if you want a rack and pinion it is the way to do it, and while I don't want/need one other people do, and that's fine. I just want people to be real about what the advantages and disadvantages really are.

Denny, I want to echo Blu’s sentiment and tell you thank you for offering your kits. I might come across like I am opposed to aftermarket kits, but I’m not. I appreciate that you offer the option, and I think your kit is a great solution. If I had the funds and the need, yours is the kit I would buy without a doubt.

 

[Mopar Virgin]

I've never had an issue with one of those jam nuts coming loose. Torque to spec. A couple drops of loctite would be fine for peace of mind, but I don't use any. You'd actually need to have BOTH jam nuts come loose for the setting to change, and then the adjuster would have to turn too.

And yes, the adjustments do help a lot in the real world. The camber bolts are only good for like +/- 1.3° if I remember right. Which is why without offset bushings most folk struggle with getting more than a couple degrees of + caster. With the SPC control arms you have a much larger adjustable range. Like I run +6.5° of caster and -1° of camber and I have a ton of adjustment left still. And changing the alignment is a lot easier.

Do I fool with it now that I have it dialed in? No, not really. But I'm not doing events or track days. It's something you could change from one track to another if you knew the track and your car. But, in the process of dialing it in I've run everywhere from -.5° of camber and +3.5° of caster all the way up to -1.5° of camber and +8° of caster. So I settled on my current specs after running through a large range of adjustment. Now granted not all of that was with the SPC's, I started with 73+ UCA's and offset bushings and used a non adjustable set of tubular UCA's before going to the SPC's. But with the SPC's I could have done all of it without ever changing out suspension components.



Nothing is really "wrong" with the MII spindle, it's actually a super adaptable suspension which is why it's been adopted by the hot rodding world so wholeheartedly. But it's the wrong question - what's wrong with the '73 A-body Mopar spindle? Or the FMJ spindle? While some of the aftermarket support is new (which is awesome!), there are lots of brake options for them now too.

So, what is the '78 MII spindle doing for you that you can't do with a '73+ Mopar spindle? First one is easy, it's set up for rear steer so a rack and pinion works without terrible Ackerman or an impossible steering shaft angle. Got it.

But what does the camber gain look like? How does it change the roll center? What does it do for your bump steer? Or yeah, turning radius?

And if you're using the A-body UCA mounting points and UCA's, well, you're already keeping a significant amount of Mopar suspension geometry. So what is improving, other than getting a rack and some header clearance?

And that's the thing I don't see anyone talk about. Or publish, for that matter. If the suspension geometry was so much better, why not publish that information? Why not have detailed analysis of all the ways a coil-over conversion will handle better?

That's the bottom line for me. A coil-over conversion gets you a rack and pinion and some header space. The downside is it loads the Mopar chassis in a way that's different than what is was designed for, and that's not a small thing (although it can be addressed). Are there some geometry changes? Yes. But like anything, there are pros and cons. And that gets back to what Peter said, most of the people buying HDK's, or AlterK's, aren't doing it because they understand the differences in suspension geometry. They see a rack a pinion, they see coil overs, and they're more familiar with those things than with torsion bars. They see a complete package they can just write a check for instead of doing some research to understand the suspension they've got and what they can do to improve it.

And I'm not trying to single out the MII spindle, the same can be asked of the Corvette spindle based suspension too. What does it actually get you? I can get 15" rotors with GT500 calipers for a 73+ Mopar spindle if brakes are the only thing. How does that system improve the suspension geometry, and therefore the handling of the car? Or, is it just shiny new parts that sound cool? "Yeah, it's got a full suspension conversion using Corvette spindles". Cool, but if it doesn't handle any better than a Mopar with torsion bars and 73+ spindles, what's the point? Although I'm sure there are already B/E body guys lining up to buy that suspension, got to be the most expensive, latest and greatest. And very few of them probably have any idea about why it's actually better, IF it actually is.

Okay @72bluNblu This recent explanation you posted makes some more sense to me. Your point about "what does it get me" versus "latest and greatest" does play into this a bit, as I have money and ascetics do matter. But the big thing is that I'm a newbie to cars and my friend is only familiar building Chevys and Fords -- This his first and only MOPAR project, and we do not have anyone in our circle who is. So, going back to your bill-of-materials, it looks overwhelming and I have no blueprint or instructions to assemble it. This is not going to be a hi-performance car. Hoping we can juice-up the /6 to 250HP+ with low-end torque to spin the wheels once-in-blue-moon, but mostly it will be a twice a week driven car in the Tucson area to run around in and turn heads (I hope) when the unique build is done, along with attending events in the general area.

One BIG THING you brought up, that I'd like to understand how to address if we go the turnkey route via QA1, HDK or RMS is your statement that they load "the MOPAR chassis in a way that's different than what is was designed for, and that's not a small thing (although it can be addressed)". Could you explain a bit more about the concern and what you'd suggest to compensate/remediate it?

 

[HemiDenny]

That seems like a huge exaggeration to me. If anything, I would guess that the Reilly kit isn’t much lighter compared to an OEM k-frame setup and similar in weight to a QA1 k-frame. And the HDK is probably similar in weight to the stock setup when the full hoop setup is included. But just my guess. Maybe you meant 12 pounds? Anything to back up that 120+ pound savings?

For what it is worth, years ago I compared a manual rack / no sway bar HDK with complete coil over package / upper shock mounts / support hoops to OEM K-frame / manual box steering assembly / no sway with 318 torsion bars.......The HDK was 29.8 lbs lighter. My goal was to compare as equivalent as possible. I will get the scales out Monday to compare a power rack to the OEM power box (got both on the shelf) .....my bet is another 20lbs lighter minimum.

I purposely did not include sway bars / brake packages / P/S pumps or anything else that can be modified / lightened regardless of suspension.

The fact that I own OEM suspension and HDK packaged Dusters should tell you...... (like Jesus) I love them all, Hot Rodding 101....do what YOU want, based on what you have to spend and for me personally, what I can do different from everybody else. I'm just look at something and think...what if I did it this way. I know, it is a disease.

I have spoken to many and once they told me their budget and what they were wanting, advised them to rebuild, update, and beef up the OEM. Last thing I want to see is a 60's-70's Mopar sitting in the corner with a new suspension (of any kind / brand)...but collecting dust because there is no money remaining to even get it running.

And a big humble "Thank You" to all....love all the ideas and input.....I learn something new all the time.

 

[HemiDenny]

.... I can't speak for anyone else but , trust me, I didn't spend all this money converting because it "looked pretty" .
Cheers!!

I like pretty......

but for some of us....it's what about what you do NOT see.

 

[Super-Cuda]

1) Yup, makes sense. Some engine swaps that aren't well supported don't have good header options. I would argue that there are a lot of swaps that are pretty well supported, but, that mostly boils down to anything *I* want to run has a least a couple options. So I get that.

2) We've been through this. It's not that much weight savings

• ~50 lbs lighter than the OE K member and suspension with factory power steering (vs HDK w/ power rack)
• ~35 lbs lighter than an OE K member and suspension using a Borgeson power steering box (vs a power rack)
• ~31 lbs lighter than an OE K and suspension w/manual steering (vs a manual rack)

Those are vs. stock mopar parts too, and using 1" torsion bars for that weight. If you install tubular LCA's, aluminum strut rods etc there is additional weight savings to be had. The QA1 LCA's save about 8 lbs. The Qa1 K saves about the same. Just that knocks 16 lbs off.

And yes, if you go OE K and OE power steering to an HDJ with a manual rack the savings is about 70 lbs, but that's not a like-to-like comparison. The OE power steering is a boat anchor, even going from OE power steering to OE manual steering saves 40lbs. If you compare the OE K and manual steering to an HDK and power rack it's only a 9 lb savings. Again, with factory parts, this means you can have a factory K and manual steering weigh less with the right aftermarket parts. But that's comparing manual to power again.

A more detailed break down is here Anybody running the RMS AlterKation? Was it really worth the cost?

3) Gets you a rack and pinion. Can't argue that much, if you really want a rack and pinion that's the best way to do it. I personally don't understand the need, I think a lot of people are comparing worn out steering/suspension parts to a new rack. But it's a good reason if that's what you want.



Sure, but I can get ALL of those alignment numbers with just a set of SPC UCA's, and everything else bone stock factory. Let alone all of the other stuff I usually upgrade. Now with a 3/4" ride height increase you probably do have a geometry improvement vs torsion bars, because you have more control over spindle heights and stuff. The torsion bar system does not like added ride height, and the best geometry occurs with some modest lowering.

I just hate it when people say stuff like they "need" a coil-over conversion to improve handling. No, you don't. And adding a rack and pinion doesn't make you faster. 10 years ago there wasn't nearly as much aftermarket support for the torsion bar system, now you can achieve a lot of the same improvements with off the shelf aftermarket parts.

And again, thanks Denny. For supporting the community and providing a great suspension set up. I mean, if you want a rack and pinion it is the way to do it, and while I don't want/need one other people do, and that's fine. I just want people to be real about what the advantages and disadvantages really are.



120 lbs where? No sir. Weight savings of actual parts are posted above.

Sorry, I should have been more specific. I also included the savings using the Street-Lynx rear suspension as well.


Heres what Motortrend had to say whick I feel is accurate. Unless I see the parts on a weigh scale I'll stick to my statement.

Convert Any Mopar Suspension to Coilovers and Make Room for Mods

 

[72bluNblu]

Okay @72bluNblu This recent explanation you posted makes some more sense to me. Your point about "what does it get me" versus "latest and greatest" does play into this a bit, as I have money and ascetics do matter. But the big thing is that I'm a newbie to cars and my friend is only familiar building Chevys and Fords -- This his first and only MOPAR project, and we do not have anyone in our circle who is. So, going back to your bill-of-materials, it looks overwhelming and I have no blueprint or instructions to assemble it. This is not going to be a hi-performance car. Hoping we can juice-up the /6 to 250HP+ with low-end torque to spin the wheels once-in-blue-moon, but mostly it will be a twice a week driven car in the Tucson area to run around in and turn heads (I hope) when the unique build is done, along with attending events in the general area.

One BIG THING you brought up, that I'd like to understand how to address if we go the turnkey route via QA1, HDK or RMS is your statement that they load "the MOPAR chassis in a way that's different than what is was designed for, and that's not a small thing (although it can be addressed)". Could you explain a bit more about the concern and what you'd suggest to compensate/remediate it?

Actually, the blue print and assembly instructions are easy, you can just download the Factory Service Manual right here for your '68 Barracuda https://www.mymopar.com/downloads/servicemanuals/1968_Plymouth_Service_Manual.zip Shows you how to do everything. And the aftermarket parts included come with their own instructions where they differ from the FSM.

And that list I posted makes for a full on autoX monster with the right tuning. With a /6 you do not need all of that stuff, I'd leave off the QA1 K member right off the bat. And although its always a good idea, you don't need to do anything to the factory K member as long as it's straight and nothing is damaged.

As for the chassis loading, it's one of the biggest differences with the torsion bar suspension. The torsion bars twist, so, the vertical suspension movement is translated into radial loads. Those loads are carried by the K frame and the torsion bar crossmember. So, all of the heavy chassis components that carry suspension loads are down low, keeping the CG down. And unlike a strut, coil, or coilover suspension there is no need for a heavily reinforced suspension tower out in front of the firewall to mount the suspension to. Those suspensions all take the vertical suspension movement and just translate it into vertical suspension loads- so you need a big old suspension tower to carry it. On a Mopar, because the torsion bars put all the loads into the K frame and crossmember the shock tower is not built to carry the weight of the car. And, the frame rails themselves are not triangulated very well with the firewall. Suspension loads are low, not high. That said, the downside to the Mopar chassis is that it is not reinforced well up high because it wasn't carrying suspension load there, and you get things like "cowl shake". Basically there's flex between the rails and the firewall/cowl.

The coil-over conversions load the chassis vertically, which is where the Mopar chassis is weak. Even with torsion bar suspensions the chassis benefits from triangulation. Look at US Cartools inner fender stiffeners Mopar A Body Inner Fender Shock Tower Brace Kit . From their website

There are also more obvious and obtrusive ways to do this, like the J-bars on my Duster which go the whole way, triangulated the front of the frame rail, tying it to the shock mount, and then the firewall

RMS deals with this by mounting their coil-overs to a tower built into their K-member. But as Denny pointed out, that limits the length of the coil-over. The HDK uses the Mopar shock mount, but adds those shock tower hoops to tie the shock tower back to the frame. Both take care of the issue of mounting the coil-over, but neither really address the frame rail to cowl/firewall issue of putting a suspension that creates vertical loads on a chassis that was designed to carry the loads radially in the cross members. Which is where the inner fender braces, J-bars, etc come from.

For what it is worth, years ago I compared a manual rack / no sway bar HDK with complete coil over package / upper shock mounts / support hoops to OEM K-frame / manual box steering assembly / no sway with 318 torsion bars.......The HDK was 29.8 lbs lighter. My goal was to compare as equivalent as possible. I will get the scales out Monday to compare a power rack to the OEM power box (got both on the shelf) .....my bet is another 20lbs lighter minimum.

I purposely did not include sway bars / brake packages / P/S pumps or anything else that can be modified / lightened regardless of suspension.

The fact that I own OEM suspension and HDK packaged Dusters should tell you...... (like Jesus) I love them all, Hot Rodding 101....do what YOU want, based on what you have to spend and for me personally, what I can do different from everybody else. I'm just look at something and think...what if I did it this way. I know, it is a disease.

I have spoken to many and once they told me their budget and what they were wanting, advised them to rebuild, update, and beef up the OEM. Last thing I want to see is a 60's-70's Mopar sitting in the corner with a new suspension (of any kind / brand)...but collecting dust because there is no money remaining to even get it running.

And a big humble "Thank You" to all....love all the ideas and input.....I learn something new all the time.

Seems spot on to me, I got 31 lbs for manual to manual but most of my parts were weighed with a bathroom scale. So a few pounds one way or another wouldn't surprise me at all.

Sorry, I should have been more specific. I also included the savings using the Street-Lynx rear suspension as well.


Heres what Motortrend had to say whick I feel is accurate. Unless I see the parts on a weigh scale I'll stick to my statement.

Convert Any Mopar Suspension to Coilovers and Make Room for Mods

Ok, so most of that weight savings comes from the rear suspension swap not the front then. I've got no issues with the rear conversions, leaf springs are pretty darn basic and not all that easy to "tune". Triangulated 4-links have their own particular pros/cons, but all suspension does. You can still handle well with leaf springs though.

The MotorTrend article is a big nothing burger, it just says what we've already covered. Header room, rack and pinion. That's it, and here's why-

I have a T-56 Magnum in my Duster, I used the ToddRon crossmember which was designed to retain the upper hoop of the crossmember and keep the torsion bars. And I have a Milodon road race oil pan. And long tube headers. And 13" brakes. So, I have all the stuff on my car they say they went to coil-overs to address.

 

[HemiDenny]

IMHO,.... snout / J bars that attach to the 18 ga OEM vent sheet metal above the firewall is like wearing a condom with pinholes punched in it....just a matter of time until problems. There is very little structural support with that thin sheet metal. Of course, thru the firewall and attached to a cage would be excellent.

Likewise, I do not put much value in the US CAR & Tool weld in support when it comes to a coil over conversion....it may help (?) in the unibody flex department, but I do not believe it was designed or intended to take the load of the coil over requirement.

But what is time-tested and proven..... the HDK upper shock mount (now available in (optional) .250 thick aluminum to trim another 4 lbs off) and chromoly support hoops. 100% bolt on, no welding or cutting. HDK re-enforces the stamped OEM upper shock mount while transferring the vertical load back to the OEM frame rails thru the HDK chromoly support hoops / hardware. It all remains hidden too... incognito to keep the OEM look. 25 years on the job....zero defects. Lets see the OEMs match that.

Pictured with the HDK exclusive ride height simulators included with every HDK coil over / rack and pinion package and take the guesswork out of which length shock best fits the builders desired ride height. With the combination of standard height or 2" drop spindles (at no extra charge) and three shock length selections, HDK offers the ability of over 5-1/2 inches of ride height variance. At HDK....one size / one look does NOT fit all.

 

[72bluNblu]

IMHO,.... snout / J bars that attach to the 18 ga OEM vent sheet metal above the firewall is like wearing a condom with pinholes punched in it....just a matter of time until problems. There is very little structural support with that thin sheet metal. Of course, thru the firewall and attached to a cage would be excellent.

Matter of time? How about 30k street miles? Look the same as the day I installed them, crappy MIG welds and all.

J-bars are no different than ANY cage installed in a unibody car. What do you weld to? Sheet metal. What are the frame rails? Sheet metal. You use a landing plate on the tube to capture enough surface area to spread the load that you want to carry. On the J bars on my car the lower edge of the landing plate is welded to the seam between the firewall and the cowl, and is tied into the corner that makes up the base of the A-pillar. I could have done it a little better and gone around the corner and captured the seam where the inner fender attaches too, but it's already tied into one of the strongest corners on the chassis. So, no, I'm calling BS on that.

And really, they're just there to stop the flex between the frame rail and the firewall/cowl. It shouldn't be a large force they're carrying, especially on a torsion bar suspended car. They eliminate cowl shake, and since mine are also tied together at the front (tubular lower radiator support), they resist twisting in the front of the car as well.

Likewise, I do not put much value in the US CAR & Tool weld in support when it comes to a coil over conversion....it may help (?) in the unibody flex department, but I do not believe it was designed or intended to take the load of the coil over requirement.

Well, when US Cartool designed them they were for improving chassis flex on the unibody, not for backing up coil overs. But structurally they box the frame, firewall, cowl, and upper shock mount. They also form a decent sized structural member if you consider the inner fender as the opposite side. Not all that different than the US Cartool subframes using the floor pan and the top of the box. It basically makes a frame stub that ties in the top of the shock mount, adding additional resistance to vertical flex between the cantilever frame rail and the cowl, which normally is just supported by the inner fender. They capture that whole corner between the firewall, cowl and inner fender, so they're pretty strong.

But what is time-tested and proven..... the HDK upper shock mount (now available in (optional) .250 thick aluminum to trim another 4 lbs off) and chromoly support hoops. 100% bolt on, no welding or cutting. HDK re-enforces the stamped OEM upper shock mount while transferring the vertical load back to the OEM frame rails thru the HDK chromoly support hoops / hardware. It all remains hidden too... incognito to keep the OEM look. 25 years on the job....zero defects. Lets see the OEMs match that.

Right, no argument on the hoops supporting the shock tower, they do. Personally I think the "bolt in" feature is attractive for home installs, but like bolt in subframe connectors they would work a lot better welded int. But in either case they do NOTHING to reinforce the largely cantilevered frame rail. The shock tower and hoop become a structural tower to support the coil-over, but, the frame rail that wasn't attached in a way to support a vertical load like that is left untouched as far as support to the rest of the chassis. Same issue with the RMS, the tower for the coil over mount is strong, but the up and down flex between the frame rail and firewall/cowl is not addressed at all. That's the weak spot, because normally he suspension loads were translated into radial forces in the K member. Much less duty for the frame rails in the torsion bar suspension.

Clearly both the HDK and the RMS AlterK have both been on the road for quite some time. But a lot of those applications are getting additional chassis stiffening, and I'm sure quite a lot of them aren't being subjected to autoX beatings and road courses. I'm sure some are, but, what's the overlap to other chassis reinforcements?

There's no way I'd run a coil-over conversion without more chassis reinforcement on the front of the car, rails to firewall/cowl.

 

[HemiDenny]

My comment / point on the snout bars welded to the vent area and the US Car and Tool supports was in regards to either being utilized to take the load of a coil over. If used strictly to somehow stiffen the chassis I would hope you would have zero issues because I don't think they are really doing anything of significance. Maybe I read your post to fast, I thought you were pointing both out as possible ways to re-enforce the uni-body to handle a coil over load.

I'm sure you realize there are different thicknesses for components of our unibodies....and from what I have experienced, the vent area is among the thinnest. If you like it...good for you, but IMO the ends (weight) do not justify the means (strengthen function). That is just how I see it, but your car....your bars

Once again, just my opinion, your opinion (which I often respect) and others may vary. .....remember, this is a discussion, not a lecture.

 

[racerjoe]

My comment / point on the snout bars welded to the vent area and the US Car and Tool supports was in regards to either being utilized to take the load of a coil over. If used strictly to somehow stiffen the chassis I would hope you would have zero issues because I don't think they are really doing anything of significance. Maybe I read your post to fast, I thought you were pointing both out as possible ways to re-enforce the uni-body to handle a coil over load.

I'm sure you realize there are different thicknesses for components of our unibodies....and from what I have experienced, the vent area is among the thinnest. If you like it...good for you, but IMO the ends (weight) do not justify the means (strengthen function). That is just how I see it, but your car....your bars

Once again, just my opinion, your opinion (which I often respect) and others may vary. .....remember, this is a discussion, not a lecture.

Denny, any percentage estimation on many cars with your K-member get lots of street miles and/or auto-x or track use? I'm not poking the bear, I'm truly curious. I think we all know most people sit in lawn chairs behind their cars in parking lots. This gets back to people wanting to be able to say they have a rack and coil overs and really could care less about any improvements. It's like those guys with the blown 632 and the car never exceeds 20mph.

 

[HemiDenny]

Denny, any percentage estimation on many cars with your K-member get lots of street miles and/or auto-x or track use? I'm not poking the bear, I'm truly curious. I think we all know most people sit in lawn chairs behind their cars in parking lots. This gets back to people wanting to be able to say they have a rack and coil overs and really could care less about any improvements. It's like those guys with the blown 632 and the car never exceeds 20mph.

my best guestimate....
90%..... street / hot rod
10% .....drag race
1% or less auto X......might be more with the intent, but I doubt if they ever see the track.

99% HDK customers tell me they want their muscle car.....
1) to have a the modern steering feel with greater high speed stability
2) be easier to work on especially header /exhaust installation
3) easy adaption of multiple engine combinations
4) exhaust that does not rattle (against the torsion bars)
5) the stance they want.

HDK strives to check all the boxes. Rarely do they ask about weight reduction....which it has... or application for auto x events.

I admire what you (and a few others) do with your car, especially after seeing the video of the guy crashing his Barracuda into the cement barrier at an auto X event in Calif (?). **** happens.

 

[Mopar Virgin]

Matter of time? How about 30k street miles? Look the same as the day I installed them, crappy MIG welds and all.

J-bars are no different than ANY cage installed in a unibody car. What do you weld to? Sheet metal. What are the frame rails? Sheet metal. You use a landing plate on the tube to capture enough surface area to spread the load that you want to carry. On the J bars on my car the lower edge of the landing plate is welded to the seam between the firewall and the cowl, and is tied into the corner that makes up the base of the A-pillar. I could have done it a little better and gone around the corner and captured the seam where the inner fender attaches too, but it's already tied into one of the strongest corners on the chassis. So, no, I'm calling BS on that.

And really, they're just there to stop the flex between the frame rail and the firewall/cowl. It shouldn't be a large force they're carrying, especially on a torsion bar suspended car. They eliminate cowl shake, and since mine are also tied together at the front (tubular lower radiator support), they resist twisting in the front of the car as well.



Well, when US Cartool designed them they were for improving chassis flex on the unibody, not for backing up coil overs. But structurally they box the frame, firewall, cowl, and upper shock mount. They also form a decent sized structural member if you consider the inner fender as the opposite side. Not all that different than the US Cartool subframes using the floor pan and the top of the box. It basically makes a frame stub that ties in the top of the shock mount, adding additional resistance to vertical flex between the cantilever frame rail and the cowl, which normally is just supported by the inner fender. They capture that whole corner between the firewall, cowl and inner fender, so they're pretty strong.



Right, no argument on the hoops supporting the shock tower, they do. Personally I think the "bolt in" feature is attractive for home installs, but like bolt in subframe connectors they would work a lot better welded int. But in either case they do NOTHING to reinforce the largely cantilevered frame rail. The shock tower and hoop become a structural tower to support the coil-over, but, the frame rail that wasn't attached in a way to support a vertical load like that is left untouched as far as support to the rest of the chassis. Same issue with the RMS, the tower for the coil over mount is strong, but the up and down flex between the frame rail and firewall/cowl is not addressed at all. That's the weak spot, because normally he suspension loads were translated into radial forces in the K member. Much less duty for the frame rails in the torsion bar suspension.

Clearly both the HDK and the RMS AlterK have both been on the road for quite some time. But a lot of those applications are getting additional chassis stiffening, and I'm sure quite a lot of them aren't being subjected to autoX beatings and road courses. I'm sure some are, but, what's the overlap to other chassis reinforcements?

There's no way I'd run a coil-over conversion without more chassis reinforcement on the front of the car, rails to firewall/cowl.

Any thoughts on this helping provide the structural support you have spoken about? ...

PM1203 - 1967-75 Mopar A-Body Inner Fender Braces

 

[go-fish]

Any thoughts on this helping provide the structural support you have spoken about? ...

PM1203 - 1967-75 Mopar A-Body Inner Fender Braces

Those are USCartool pieces sold by Classic Industries

when US Cartool designed them they were for improving chassis flex on the unibody, not for backing up coil overs. But structurally they box the frame, firewall, cowl, and upper shock mount. They also form a decent sized structural member if you consider the inner fender as the opposite side. Not all that different than the US Cartool subframes using the floor pan and the top of the box. It basically makes a frame stub that ties in the top of the shock mount, adding additional resistance to vertical flex between the cantilever frame rail and the cowl, which normally is just supported by the inner fender. They capture that whole corner between the firewall, cowl and inner fender, so they're pretty strong

 

[72bluNblu]

My comment / point on the snout bars welded to the vent area and the US Car and Tool supports was in regards to either being utilized to take the load of a coil over. If used strictly to somehow stiffen the chassis I would hope you would have zero issues because I don't think they are really doing anything of significance. Maybe I read your post to fast, I thought you were pointing both out as possible ways to re-enforce the uni-body to handle a coil over load.

I'm sure you realize there are different thicknesses for components of our unibodies....and from what I have experienced, the vent area is among the thinnest. If you like it...good for you, but IMO the ends (weight) do not justify the means (strengthen function). That is just how I see it, but your car....your bars

Once again, just my opinion, your opinion (which I often respect) and others may vary. .....remember, this is a discussion, not a lecture.

Of course I’m aware there’s multiple gauges of sheet metal on these cars, I’ve welded to all of them so yeah, I’m aware.

I’m sure you’re aware that unibodies are a sum of their parts and that seams, joints, contours and stamped reinforcements are more important than just the simple gauge thickness. The “vent area” as you call it, the upper cowl, is very strong in the corners (where the J bars attach) because it is tied into the seam with the firewall, the seam with the foot box/floor pan, and the seam with the a-pillar and inner fender. Stay close to the corners and you’re dealing with one of the strongest parts of the car. That’s not the “vent area”.

Regardless, I’m more than happy with my J-bars and the noticeable difference in chassis stiffness they made when I added them. Running 275’s up front shows you a lot of flex in these chassis that running tires typical of street drivers and drag racers will not.

US Cartool and XV Engineering have done some of the most extensive chassis testing on these cars, and both offer varying styles of inner fender braces. To reinforce the area between the shock tower and firewall/cowl area.

Any thoughts on this helping provide the structural support you have spoken about? ...

PM1203 - 1967-75 Mopar A-Body Inner Fender Braces

Exactly like go-fish said, those are the US Cartool braces just being sold by Classic.

Same ones I installed on my ‘71 Dart. They’re inside the fender so they’re less visible than J-bars in your engine compartment, but the way they tie the sock tower into the inner fender, firewall and cowl creates a significant structural member similar to areas of the frame or rockers. The aftermarket companies that have tested chassis flex in these cars all offer reinforcement to that particular area. And it makes sense based on how the original chassis was (and wasn’t) loaded by the torsion bars.

 

[HemiDenny]

Of course I’m aware there’s multiple gauges of sheet metal on these cars, I’ve welded to all of them so yeah, I’m aware.

I’m sure you’re aware that unibodies are a sum of their parts and that seams, joints, contours and stamped reinforcements are more important than just the simple gauge thickness. The “vent area” as you call it, the upper cowl, is very strong in the corners (where the J bars attach) because it is tied into the seam with the firewall, the seam with the foot box/floor pan, and the seam with the a-pillar and inner fender. Stay close to the corners and you’re dealing with one of the strongest parts of the car. That’s not the “vent area”.

Regardless, I’m more than happy with my J-bars and the noticeable difference in chassis stiffness they made when I added them. Running 275’s up front shows you a lot of flex in these chassis that running tires typical of street drivers and drag racers will not.

US Cartool and XV Engineering have done some of the most extensive chassis testing on these cars, and both offer varying styles of inner fender braces. To reinforce the area between the shock tower and firewall/cowl area.



Exactly like go-fish said, those are the US Cartool braces just being sold by Classic.

Same ones I installed on my ‘71 Dart. They’re inside the fender so they’re less visible than J-bars in your engine compartment, but the way they tie the sock tower into the inner fender, firewall and cowl creates a significant structural member similar to areas of the frame or rockers. The aftermarket companies that have tested chassis flex in these cars all offer reinforcement to that particular area. And it makes sense based on how the original chassis was (and wasn’t) loaded by the torsion bars.

welding to the cowl / vent area for anything is not in my playbook, the windshield area is the last place on the car I want any kind of additional stress pushing or pulling. JMHO But hey, as long as you like it....go for it.

 

[kesteb]

For all of the work that that is needed for the Speedtec solution, or for that matter the all of the body reinforcement for the other solutions. Why not just channel the body over a Art Morrison Pro Street frame?

 

[HemiDenny]

For all of the work that that is needed for the Speedtec solution, or for that matter the all of the body reinforcement for the other solutions. Why not just channel the body over a Art Morrison Pro Street frame?

the HDK requires drilling a grand total of 6 holes. Zero welding or modifying. By the time most got their Morrison Pro Street frame off the forking lift and uncrated, the (pre-assembled) HDK is ready for the alignment shop.

BTW, the Art Morrison chassis installs, and all other full chassis installs for that matter I have witnessed, about all that is left of your Mopar is the sheet metal skin. Indeed, they can be very trick, but not for most of us....just too much $$$ and even IF we did the install ourselves, a hell of lot of work / modification.

 

[kesteb]

True, but it does solve a problem with 50 years of corrosion on a uni-body chassis. The Speedtec solution may cost just as much as a Art Morrison chassis. But with all the benefits of those 50 years of corrosion.

There is no simple solution to this perceived problem. And everybody has there preferences.

 

[72bluNblu]

welding to the cowl / vent area for anything is not in my playbook, the windshield area is the last place on the car I want any kind of additional stress pushing or pulling. JMHO But hey, as long as you like it....go for it.

Wait, so, you said before you "don't think they are really doing anything of significance". Which makes sense considering you don't offer any way to reinforce that area. Now you're implying that the added stress they're going to carry to the "windshield area" is somehow going to be a problem?

C'mon man.

The "windshield area" is supported and made up from the A-pillars, which are one of the strongest points on the car. They do a lot more than just hold the windshield, they're one of the major structural components of the chassis. And tying J bars or inner fender supports into the cowl and firewall and therefore into the structures that support the A-pillars doesn't just add stress, it disperses load. The chassis reinforcement doesn't have a one way switch, they may share some load from the forward part of the frame rails and chassis but they will also disperse load from that area forward as well. Chassis reinforcement spreads the load over more area, which reduces the impact on any single component. That's true always, but it's especially important on a unibody.

And again, it's not just a matter of "liking them". I've driven my Duster with and without them and I can tell you that they make a tangible difference. Especially with 1.12" torsion bars and 275/35/18's up front and 295/40/18's out back. Are they necessary for a street cruiser? Probably not. But that's not nearly the same as saying they're not significant.

There's absolutely no way I'd run any coil over conversion without additional chassis reinforcement to compensate for the change in how the chassis is loaded. That's my bottom line. You can't say the coil over suspension doesn't load the chassis differently, clearly it does. It's just a fact of how the different suspension designs disperse load into the chassis.

True, but it does solve a problem with 50 years of corrosion on a uni-body chassis. The Speedtec solution may cost just as much as a Art Morrison chassis. But with all the benefits of those 50 years of corrosion.

There is no simple solution to this perceived problem. And everybody has there preferences.

It doesn't solve the problem of 50 years of corrosion on the unibody chassis, it just ties a unibody chassis with 50 years of corrosion to a frame. That frame doesn't work independently of the body you attach it to, it has to work with it.

It comes back to "what does it get you". C6 suspension. Maybe IRS if you spring for the big bucks, otherwise a 3 or 4 link you can add without a full chassis replacement.

The Red Brick was able to hang with a C6 vette, just torsion bars and leaf springs. The Art Morrison chassis sure is a fancy gig, but it's just another way people that don't know anything about suspension or chassis spend a lot of money so they don't have to learn anything about suspension or chassis. They do not provide some unobtainable level of performance, they just make it easy to write a big check to a shop to build you a fancy show car.

 

[HemiDenny]

Wait, so, you said before you "don't think they are really doing anything of significance". Which makes sense considering you don't offer any way to reinforce that area. Now you're implying that the added stress they're going to carry to the "windshield area" is somehow going to be a problem?

C'mon man.

The "windshield area" is supported and made up from the A-pillars, which are one of the strongest points on the car. They do a lot more than just hold the windshield, they're one of the major structural components of the chassis. And tying J bars or inner fender supports into the cowl and firewall and therefore into the structures that support the A-pillars doesn't just add stress, it disperses load. The chassis reinforcement doesn't have a one way switch, they may share some load from the forward part of the frame rails and chassis but they will also disperse load from that area forward as well. Chassis reinforcement spreads the load over more area, which reduces the impact on any single component. That's true always, but it's especially important on a unibody.

And again, it's not just a matter of "liking them". I've driven my Duster with and without them and I can tell you that they make a tangible difference. Especially with 1.12" torsion bars and 275/35/18's up front and 295/40/18's out back. Are they necessary for a street cruiser? Probably not. But that's not nearly the same as saying they're not significant.

There's absolutely no way I'd run any coil over conversion without additional chassis reinforcement to compensate for the change in how the chassis is loaded. That's my bottom line. You can't say the coil over suspension doesn't load the chassis differently, clearly it does. It's just a fact of how the different suspension designs disperse load into the chassis.

I attempted to make three points....

1) I do not think welding to the cowl area does anything significant as far as strengthening is concerned...too thin.

2) if indeed I was looking for additional strength for the shock tower, I would not pick the cowl area.

3) as long as you like it...it is all good.

 

[Super-Cuda]

Wait, so, you said before you "don't think they are really doing anything of significance". Which makes sense considering you don't offer any way to reinforce that area. Now you're implying that the added stress they're going to carry to the "windshield area" is somehow going to be a problem?

C'mon man.

The "windshield area" is supported and made up from the A-pillars, which are one of the strongest points on the car. They do a lot more than just hold the windshield, they're one of the major structural components of the chassis. And tying J bars or inner fender supports into the cowl and firewall and therefore into the structures that support the A-pillars doesn't just add stress, it disperses load. The chassis reinforcement doesn't have a one way switch, they may share some load from the forward part of the frame rails and chassis but they will also disperse load from that area forward as well. Chassis reinforcement spreads the load over more area, which reduces the impact on any single component. That's true always, but it's especially important on a unibody.

And again, it's not just a matter of "liking them". I've driven my Duster with and without them and I can tell you that they make a tangible difference. Especially with 1.12" torsion bars and 275/35/18's up front and 295/40/18's out back. Are they necessary for a street cruiser? Probably not. But that's not nearly the same as saying they're not significant.

There's absolutely no way I'd run any coil over conversion without additional chassis reinforcement to compensate for the change in how the chassis is loaded. That's my bottom line. You can't say the coil over suspension doesn't load the chassis differently, clearly it does. It's just a fact of how the different suspension designs disperse load into the chassis.



It doesn't solve the problem of 50 years of corrosion on the unibody chassis, it just ties a unibody chassis with 50 years of corrosion to a frame. That frame doesn't work independently of the body you attach it to, it has to work with it.

It comes back to "what does it get you". C6 suspension. Maybe IRS if you spring for the big bucks, otherwise a 3 or 4 link you can add without a full chassis replacement.

The Red Brick was able to hang with a C6 vette, just torsion bars and leaf springs. The Art Morrison chassis sure is a fancy gig, but it's just another way people that don't know anything about suspension or chassis spend a lot of money so they don't have to learn anything about suspension or chassis. They do not provide some unobtainable level of performance, they just make it easy to write a big check to a shop to build you a fancy show car.

You stated " The Red Brick was able to hang with a C6 vette, just torsion bars and leaf springs."


I think you are oversimplifying how the Red Brick can stay with a Vette.


" Here's the builder's description of "The Red Brick"

1968 Plymouth Valiant 427 Engine Swap - Mopar Muscle Magazine

Mostly original paint (doors and Dr fender repainted, don't quite match), all steel body, torque boxes, frame connectors, 6 pt (non intrusive) cage, firewall to frame rail bars underhood, XV front chassis (radiator) brace.

Engine, 7.0 liter Small Block dynoed at 519 hp @ 5800, 506 lb/ft @ 4100: 340 resto block, AN connections at oil filter. HV pump, remote filter, 3 QT Accusump mounted behind passenger seat. K1 4.125” stroke crank, K1 rods, JE pistons 10.5 compression. Edelbrock Aluminum heads - Stage 3 ported by Hughes Engines with 2.08 intake valves. Comp roller cam 236/236 at .050 with .545”/.537” lift, Comp solid roller lifters, Comp 1.5 ratio rockers, Milodon road race oil pan, MSD E-Curve distributor. Edelbrock Victor 340 intake ported by Shady Dell, BLP 650 CFM carb. TTI ceramic coated headers, TTI 2.5” X-pipe exhaust with Magnaflow mufflers.

Trans: A-833 with 2.66 first gear in Passon Performance aluminum case. Hurst shifter solid mount. Steel flywheel - McLeod clutch

Rear: 66-7 B-Body housing with 2.94 center section, Dr. Diff clutch type differential. Aluminum driveshaft.

Brakes: Front - Baer 6 piston, 13” two piece rotors Rear—Mustang Cobra rear disc kit from Dr. Diff. Mopar aluminum master cylinder 15/16” piston dia. Wilwood rear pressure valve - adjustable from drivers seat. Carbotech track pads all around as well as street pads for cruising.

Suspension: Front - 1.20 T-bars, 72 K frame seam welded, reinforced with FFI kit, notched for oil pan clearance, boxed for NASCAR-style Speedway Engineering sway bar, FMJ spindles, FFI upper A-arms, Lower arms boxed with AR Eng plates and setup for heim style endlink. Poly lower control arm pivots w/AR Eng retaining plates, FFI C-body tubular tie rods, FFI Stage 3 steering box with PS cooler mounted behind grille. Poly strut rod bushings. Bilstein shocks. Rear- AR Eng front hangers, F-body rear shackles, 340 rear springs with poly on both ends. Adjustable frame mounted rear sway bar .875”. Bilstein shocks. Has new 275/40/17 Falken Azenis 200 tread wear tires on 17x9 Konig wheels on all 4 corners.

Misc: trunk mounted battery, light weight Toyota 60A alternator, custom dash insert with Autometer gauges, Extra-large warning lights for oil press, H2O and volts. Aluminum radiator with SPAL sucker fan – Manual switch and thermostatically controlled. Corbeau seats with 4 pt harnesses. Heater/defrost removed, factory glass all intact, wipers & turn signals function as factory.


It takes a little more than torsion bars and leaf springs. This is a highly modified A-Body. Very very well done by someone who obviously knows suspension systems power trains and race cars.. I would guess its out of the skill realm of 90% of the members of this site. For us who don't and still want a great handling car, the kits offered by HDK and RMS come with the engineering done that performs exceptionally well and a relatively simple install.

I am in no way knocking your knowledge or expertise. I'm sure your car handles very well too.

 

[DionR]

You stated " The Red Brick was able to hang with a C6 vette, just torsion bars and leaf springs."


I think you are oversimplifying how the Red Brick can stay with a Vette.


" Here's the builder's description of "The Red Brick"

1968 Plymouth Valiant 427 Engine Swap - Mopar Muscle Magazine

Mostly original paint (doors and Dr fender repainted, don't quite match), all steel body, torque boxes, frame connectors, 6 pt (non intrusive) cage, firewall to frame rail bars underhood, XV front chassis (radiator) brace.

Engine, 7.0 liter Small Block dynoed at 519 hp @ 5800, 506 lb/ft @ 4100: 340 resto block, AN connections at oil filter. HV pump, remote filter, 3 QT Accusump mounted behind passenger seat. K1 4.125” stroke crank, K1 rods, JE pistons 10.5 compression. Edelbrock Aluminum heads - Stage 3 ported by Hughes Engines with 2.08 intake valves. Comp roller cam 236/236 at .050 with .545”/.537” lift, Comp solid roller lifters, Comp 1.5 ratio rockers, Milodon road race oil pan, MSD E-Curve distributor. Edelbrock Victor 340 intake ported by Shady Dell, BLP 650 CFM carb. TTI ceramic coated headers, TTI 2.5” X-pipe exhaust with Magnaflow mufflers.

Trans: A-833 with 2.66 first gear in Passon Performance aluminum case. Hurst shifter solid mount. Steel flywheel - McLeod clutch

Rear: 66-7 B-Body housing with 2.94 center section, Dr. Diff clutch type differential. Aluminum driveshaft.

Brakes: Front - Baer 6 piston, 13” two piece rotors Rear—Mustang Cobra rear disc kit from Dr. Diff. Mopar aluminum master cylinder 15/16” piston dia. Wilwood rear pressure valve - adjustable from drivers seat. Carbotech track pads all around as well as street pads for cruising.

Suspension: Front - 1.20 T-bars, 72 K frame seam welded, reinforced with FFI kit, notched for oil pan clearance, boxed for NASCAR-style Speedway Engineering sway bar, FMJ spindles, FFI upper A-arms, Lower arms boxed with AR Eng plates and setup for heim style endlink. Poly lower control arm pivots w/AR Eng retaining plates, FFI C-body tubular tie rods, FFI Stage 3 steering box with PS cooler mounted behind grille. Poly strut rod bushings. Bilstein shocks. Rear- AR Eng front hangers, F-body rear shackles, 340 rear springs with poly on both ends. Adjustable frame mounted rear sway bar .875”. Bilstein shocks. Has new 275/40/17 Falken Azenis 200 tread wear tires on 17x9 Konig wheels on all 4 corners.

Misc: trunk mounted battery, light weight Toyota 60A alternator, custom dash insert with Autometer gauges, Extra-large warning lights for oil press, H2O and volts. Aluminum radiator with SPAL sucker fan – Manual switch and thermostatically controlled. Corbeau seats with 4 pt harnesses. Heater/defrost removed, factory glass all intact, wipers & turn signals function as factory.


It takes a little more than torsion bars and leaf springs. This is a highly modified A-Body. Very very well done by someone who obviously knows suspension systems power trains and race cars.. I would guess its out of the skill realm of 90% of the members of this site. For us who don't and still want a great handling car, the kits offered by HDK and RMS come with the engineering done that performs exceptionally well and a relatively simple install.

I am in no way knocking your knowledge or expertise. I'm sure your car handles very well too.

I think you are reading into Blu's comment if you think he is saying that the suspension was all the Red Brick needed to keep up with the C6. I believe his point was that in addition to all the other parts, the suspension was pretty low key parts wise.

I do find it funny that what you posted was almost a direct correlation to what Blu has been saying suspension wise. Really the only trick part is the custom sway bar. The rest of it was just upgraded stock type parts.

 

[Super-Cuda]

I think you are reading into Blu's comment if you think he is saying that the suspension was all the Red Brick needed to keep up with the C6. I believe his point was that in addition to all the other parts, the suspension was pretty low key parts wise.

I do find it funny that what you posted was almost a direct correlation to what Blu has been saying suspension wise. Really the only trick part is the custom sway bar. The rest of it was just upgraded stock type parts.

I'm going to respectfully disagree.

I think its a combination of powertrain, suspension, the builders knowledge of available parts, plus racing knowledge that creates a special package such as the Brick that can outperform a Vette..

 

[DionR]

I'm going to respectfully disagree.

I think its a combination of powertrain, suspension, the builders knowledge of available parts, plus racing knowledge that creates a special package such as the Brick that can outperform a Vette..

I'm not disagreeing with you. I completely agree that the car is a package and without all of it then it won't perform to that level.

What I am saying, and what I think Blu was saying, is that when you look at the one aspect of the suspension, it didn't take a coil over kit to get there. Not ignoring the rest of the car, but looking at only the parts that are pertinent to the discussion.

Blu wasn't saying someone could duplicate the Red Brick by swapping on his parts list onto a car. Only "look what the Red Brick did with mostly stock type parts".