rough rider

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rustyswinger

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HI All,

I took my 1974 dart swinger out on her maiden voyage this weekend. About 80 miles each way. Idles like crap still, but pulled strong on the hi-way.

I have completely rebuilt this car from the ground up. The only used front end parts are the torsion bars, and disc brake spindles from my 318 parts car. I have 14 inch tires on cragar rims. Brand new rubber all around.
The car drives straight as an arrow.

When I hit a railroad track or bridge deck she handles it great! Smooth and quiet. When I hit the little frost heaves that we get in Canada, every bump is like a bang, or a clunk.

Big bumps with lots of suspension travel= smooth ride

Small bumps with short sharp impact and little suspension travel= bone jarring clunk.

thoughts?
 
Is the front sitting on the bump stops?

Idle is just tuning
 
roccodart440 said:
Is the front sitting on the bump stops?

Idle is just tuning
Click to expand...

Thank you for the reply!

The car is not on the bump stops. ( New bump stops too by the way) There is about 5/8ths of an inch gap on level ground between the bumpstop and the lower control arm.

Thinking back I should take a closer look at the upper arm bump stops, but I had clearance there too after ride height was set. ( That was last fall...I'm going to look again tonight)

One thing that bothered me was after it got back from the ride height setting and alignment ( local fountain tire dealer) I was happy all looked good. I finished installing bumpers and spare tire, and the remaining odds and ends...it was about 1/2 inch low on the passenger side. I did crank up that torsion bar about 1 full turn on the adjuster. ( yes I should get it realigned)

As for the Idle.....I cant seem to flatten it out. All brand new components except for the Carter 2BBL carb. I rebuilt it, and it seems to work great except for the idle being rough. I may have ruined the mixture screws by polishing them. I tried to be careful but there is some scoring on them, and a bit of a ridge on one. My Vacuum gauge reads about 19 inches of hg, and flutters with the idle lope. Needle also has a fast vibration, Internet tells me that's valve related......
 
5/8” between the bump stop and frame rail isn’t enough unless you’re running 1.18” or bigger torsion bars.

The suspension is bottoming out all the time, that’s why it’s riding rough. If you have stock torsion bars you need way more clearance than that.
 
72bluNblu said:
5/8” between the bump stop and frame rail isn’t enough unless you’re running 1.18” or bigger torsion bars.

The suspension is bottoming out all the time, that’s why it’s riding rough. If you have stock torsion bars you need way more clearance than that.
Click to expand...
Ok, It does sit a bit low in the front end I suppose. How much clearance is appropriate for stock T-bars that came off a 318 car?
 
rustyswinger said:
Ok, It does sit a bit low in the front end I suppose. How much clearance is appropriate for stock T-bars that came off a 318 car?
Click to expand...

If you're running stock torsion bars, you need to run the factory ride height unless you want to constantly be on the bumpstops. The method they used measured from the LCA to the ground, and A body falls under the "V and L" line in the manual. This is the factory method...
factoryalignspecs.jpg


Even at the factory ride height, with factory bump stops, you'll be hitting the bumpstops with stock bars. That's why they're that triangular shape, the bump stops were used as part of the suspension travel.
 
if you ride on the bumpstops long enough, you'll have more trouble than just a rough ride. I bought a repo'd Duster at an auction years ago, and because the PO liked the "snow plow" look, it broke the upper control arm ears and cracked the frame horns.
 
It takes some miles for new front end components to settle in.

How much tire pressure? I usually run 30-32 psi In the radials on my old junk.

Carb rebuild kits come with a new needle and seat. (Hopefully parts compatible with todays fuel) Also, go through the carb and adjust per the FSM.

And as an aside, spend some time rechecking the torque on all the bolts and nuts in the front end, including the 3 on the steering box. You might be surprised.
 
KosmicKuda said:
It takes some miles for new front end components to settle in.

How much tire pressure? I usually run 30-32 psi In the radials on my old junk.

Carb rebuild kits come with a new needle and seat. (Hopefully parts compatible with todays fuel) Also, go through the carb and adjust per the FSM.

And as an aside, spend some time rechecking the torque on all the bolts and nuts in the front end, including the 3 on the steering box. You might be surprised.
Click to expand...


Thank you for the reply.
For the carb I didn't mean needle and seat. Both are new and replaced with the kit. I'm
referring to the 2 brass mixture screws at the carb base

I have checked torque on most everything. Steering box is a good suggestion

thanks
 
rustyswinger said:
Not quite riding on them. There is clearance on flat ground
Click to expand...

Not enough. Let's put it this way. I use 1.12" torsion bars on my Duster. I have about 1" of clearance from frame to bump stop on my car. I occasionally still hit the bump stops. The wheel rate on my car is 300 lb/in with those torsion bars. With stock 318 bars, it's like 100 lb/in. So if you wanted to NEVER hit the bump stops, you'd need 3" of clearance. Now, that's not how the factory bump stops are used, so, you don't need that much. But, 5/8" is probably only 1/4 of the travel you need to have to the ride the factory intended with those bars.

rustyswinger said:
There is a fair bit of adjustment left available on my t-bars. You don't think it will be sufficient?
Click to expand...

You have should have enough adjustment to get back to the factory specs. But your ride height will be much higher. If you wanted to keep the ride height the same as it is now, you would need to change out a whole bunch of suspension parts.
 
72bluNblu said:
Not enough. Let's put it this way. I use 1.12" torsion bars on my Duster. I have about 1" of clearance from frame to bump stop on my car. I occasionally still hit the bump stops. The wheel rate on my car is 300 lb/in with those torsion bars. With stock 318 bars, it's like 100 lb/in. So if you wanted to NEVER hit the bump stops, you'd need 3" of clearance. Now, that's not how the factory bump stops are used, so, you don't need that much. But, 5/8" is probably only 1/4 of the travel you need to have to the ride the factory intended with those bars.



You have should have enough adjustment to get back to the factory specs. But your ride height will be much higher. If you wanted to keep the ride height the same as it is now, you would need to change out a whole bunch of suspension parts.
Click to expand...
This really helps.
I do believe my ride height was affected a bit by parts settling in as has been mentioned, and when the ride height was established, I wasn't at curb weight either. It is a bit too low for me the way it is now, so some lifting will improve the stance in my eyes.

I am going to reset my ride height, as close to factory as I can. ( I wish my garage floor was level...) Then I will get a wheel alignment. I have heard that the factory alignment specs aren't correct for todays radial tires... I need to research that too.


If it isn't right and cant be made to work well and look good, Then I will upgrade the torsion bars. You mentioned upgrading a whole bunch of suspension parts... which other parts were you meaning?

Thank you!
 
Correct, you don't want to use the factory alignment numbers if you're running radial tires.

Typically, you want your alignment to be somewhere in the range of -.25* to -.5* camber, +3* or more caster, and around 1/16" to 1/8" toe in for a basic street driver on radial tires. If you didn't use offset UCA bushings you may not be able to get to or much past +3* of caster, it depends on your ride height and your suspension components.

The torsion bars are probably the biggest "problem" with the stock suspension parts. These cars were undersprung right from the factory. Some of that had to do with the bias ply's they were equipped with. So, upgrading the torsion bars will do a lot as far as better handling, and if you match your suspension parts to the larger bars, better handling too. After that you run into alignment adjustment range issues, which is where the offset UCA bushings or tubular UCA's come into play. Both allow for more positive caster to be adjusted in, which is a good thing for radials.

How "crazy" you go depends on the use of the car. The larger you go with the torsion bars, the more your ride quality will benefit from better shocks. The more you lower your car, the larger the torsion bars need to be. And if you go really low, you need to change out the factory bump stops (shorter lowers, taller uppers to recenter things). Again, just depends on how extreme you go. For a car that's just a basic street driver, you don't need to get too crazy. Step up to torsion bars around the 1" mark, maybe some better shocks and the Moog k7103 offset UCA bushings and you'll do great. If you want to AutoX on the weekends, you may need to get pretty crazy depending on your expectations of performance.
 
Thank you again.
I appreciate your wisdom. I have read a few other posts you have made as have others on the offset bushings. Makes sense, wish I knew about that when I bought all my parts. Ah well.....if new T-bars are in the budget, so will new bushings be.

For now, I will see if I can improve enough to drive this summer. This car is meant to be a fun car to cruise around town with the kids. Needs to be safe, but not a high performer.
 
rustyswinger said:
Thank you again.
I appreciate your wisdom. I have read a few other posts you have made as have others on the offset bushings. Makes sense, wish I knew about that when I bought all my parts. Ah well.....if new T-bars are in the budget, so will new bushings be.

For now, I will see if I can improve enough to drive this summer. This car is meant to be a fun car to cruise around town with the kids. Needs to be safe, but not a high performer.
Click to expand...

No problem!

If you don't mind raising the ride height and getting a new alignment you can probably make do with the torsion bars you already have. You just need some more clearance to stay off the bump stops so the ride is better. And if you raise the front end some you may be able to accomplish what you need based on your application. Larger bars would be good and they'll make the car safer, but they don't necessarily have to be something you get before you can use the car as long as you don't might raising it up some. I do think they're a worthwhile addition for the long term though. PST makes a 1.03" bar that a lot of people here use successfully and are happy with.
 
72bluNblu said:
No problem!

If you don't mind raising the ride height and getting a new alignment you can probably make do with the torsion bars you already have. You just need some more clearance to stay off the bump stops so the ride is better. And if you raise the front end some you may be able to accomplish what you need based on your application. Larger bars would be good and they'll make the car safer, but they don't necessarily have to be something you get before you can use the car as long as you don't might raising it up some. I do think they're a worthwhile addition for the long term though. PST makes a 1.03" bar that a lot of people here use successfully and are happy with.
Click to expand...
Ok, I did some measuring I have O.89 on my cheapo caliper for my torsion bars.

They came off a doner V8 car 74 swinger

I didn't complete my research apparently.

Just about to order 1.03 bars from Pst.....doh....credit card has vanished from wallet.

now I wait to clear that up. If I can find them locally I have my Friday night project figured
 
Last edited:
I have rebuilt a few cars and had similar results with a harsh ride. After some research I think it may have to do with how you reassemble and torque the components. Seems there is a sequence to it....
Any opinions on this ?
 
roccodart440 said:
yeah 5/8 of and inch..... You're on the bump stops.

YOu need drop spindles or change the ride height and buy bigger tbars.
Click to expand...

You are correct. I have been educated as to my ignorance. I have ordered larger bars, as well as offsett UCA bushings, and will set my ride height properly, get an alignment when they arrive.
 
mbaird said:
I have rebuilt a few cars and had similar results with a harsh ride. After some research I think it may have to do with how you reassemble and torque the components. Seems there is a sequence to it....
Any opinions on this ?
Click to expand...
There is a great write up here in FABO about not torquing the lower bushings/bolts until after you set the ride height. I did that, but did experience some " settling" of the front end.

Also dont be dumb like me and set ride height before you have reached proper curb weight according to the FSM
 
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