Front suspension set up and wheel alignment

[Scottrico]

I need some guidance on initial set up of front suspesion and wheel alignment on my 74 Duster. I am in the process of installing a completely new front suspension which includes a new Borgeson power steering box, pst 1.08 torsion bars, Dr Diff front disk brake kit, Dr Diff front suspension kit with stock type upper control arms, steering knucles, new upper and lower ball joints, idler arm, Pitman arm, tie rod ends, Hotchkis strut rods, etc. Only parts being reused are the center link and rebuilt lower control arms (pst kit).
I have read a lot of the posts concerning torsion bar installation and wheel alignment and am aware of many of the things to consider, but what concerns me is how will my front height adjustment be affected by the fact that I have installed the mancini racing leaf springs and the rear of the car sits up higher on the right rear side because of the different spring ratings. And how will wheel alignment be accomplished with this set up? This car will be driven on the street, and only go to the drag strip once or twice a year.

 

[Demonx2]

@72bluNblu

 

[RustyRatRod]

I need some guidance on initial set up of front suspesion and wheel alignment on my 74 Duster. I am in the process of installing a completely new front suspension which includes a new Borgeson power steering box, pst 1.08 torsion bars, Dr Diff front disk brake kit, Dr Diff front suspension kit with stock type upper control arms, steering knucles, new upper and lower ball joints, idler arm, Pitman arm, tie rod ends, Hotchkis strut rods, etc. Only parts being reused are the center link and rebuilt lower control arms (pst kit).
I have read a lot of the posts concerning torsion bar installation and wheel alignment and am aware of many of the things to consider, but what concerns me is how will my front height adjustment be affected by the fact that I have installed the mancini racing leaf springs and the rear of the car sits up higher on the right rear side because of the different spring ratings. And how will wheel alignment be accomplished with this set up? This car will be driven on the street, and only go to the drag strip once or twice a year.

You don't compensate for the rear sitting unlevel with the alignment, or with the torsion bars. In other words, get it aligned to whichever specs you decide on (search the Skosh Chart) and just let it sit "wherever" it falls in the rear. If you try to compensate for the different spring rates in the rear by using the ride height in the front, you will make the rear suspension less effective on launch. Those particular springs are designed to make the car level on launch at the strip. That's why they sit driver's side down. The torque of the engine straightens the car on launch and plants the tires harder. When you get it aligned, just level up the FRONT with the torsion bars and allow it to sit unlevel in the rear. It's a Mopar thing.

 

[Scottrico]

Thanks for the speedy reply. Like many others on this forum, I prefer to do things myself. I will take your advice into consideration as I move forward and learn how to align myself.

 

[RustyRatRod]

Thanks for the speedy reply. Like many others on this forum, I prefer to do things myself. I will take your advice into consideration as I move forward and learn how to align myself.

I love doing my own alignments. I was an alignment mechanic for a long time so I really enjoy it.

 

[junkyardhero]

if you take pictures, get measurements and make notes before you pull it all apart then reassemble somewhat close to what was there, you'll be kinda sorta in the ball park to start.

from there, it's easier to dial it in that just WAG on putting stuff together.

i like to tackle it in this manner, then give everything a calibrated eyeball before breaking out the laser level and alignment tools for the fine adjustments.

just remember to torque everything to spec, and tighten the LCA's only once they're on the ground with the weight of the car and your ride height set.

 

[Kern Dog]

Unless you are really dedicated to drag racing, why settle for the rear of the car sitting out of level?
A car set up for handling can still be a good drag race car.
A car set up for drag racing is often a crappy street car.
Me? I'd get the rear to sit level, then go on with the front end work. Aim for alignment with at least 2 degrees of POSitive caster, At least 1/2 of a degree of NEGative camber and about 1/16" of total toe IN.
My '70 Charger has Mopar Performance HD leaf springs, 6 leafs per side and it sits even. It is NOT set up for drag racing but does launch well and goes straight.

I have offset upper control arm bushings which allowed me to get over 5 degrees of Positive caster! The car steers like a new car with the alignment and the Borgeson steering box.
You CAN make these old cars feel and handle like a newer car if you choose the right parts.

 

[72bluNblu]

The stock replacement UCA's will have stock style bushings as well, which isn't want you want. I'd replace those brand new UCA bushings with a set of the Moog K7103 offset bushings. Otherwise you're not going to get much of anything for positive caster, which will make your car feel like you're driving a shopping cart. With factory UCA bushings you're unlikely to make it much past the "granny" setting on the skosh chart...

And honestly the skosh chart was set up around using only offset bushings so even its caster recommendations are a bit on the conservative side IMO. I'd never run anything less than about +3.5°, which you should be able to get with offset UCA bushings, but not factory UCA bushings.

The Mancini springs I see on their website are listed as XHD's, which means they shouldn't be different rates and they should sit flat. The SuperStock springs are the ones that have different arches. Unless Mancini is doing something different, the Mopar made XHD's I have on my Challenger sit flat side to side.

 

[Scottrico]

The stock replacement UCA's will have stock style bushings as well, which isn't want you want. I'd replace those brand new UCA bushings with a set of the Moog K7103 offset bushings. Otherwise you're not going to get much of anything for positive caster, which will make your car feel like you're driving a shopping cart. With factory UCA bushings you're unlikely to make it much past the "granny" setting on the skosh chart...

View attachment 1716119236

And honestly the skosh chart was set up around using only offset bushings so even its caster recommendations are a bit on the conservative side IMO. I'd never run anything less than about +3.5°, which you should be able to get with offset UCA bushings, but not factory UCA bushings.

The Mancini springs I see on their website are listed as XHD's, which means they shouldn't be different rates and they should sit flat. The SuperStock springs are the ones that have different arches. Unless Mancini is doing something different, the Mopar made XHD's I have on my Challenger sit flat side to side.

I think I will go for the moog kit. I see it comes with two bushings. Is that for one control arm so that I would need two kits?
Are there instruction on how to orient the bushing to be able to move the front bushings away from the frame to get the top ball joints moving aft?

 

[Kern Dog]

I think I will go for the moog kit. I see it comes with two bushings. Is that for one control arm so that I would need two kits?
Are there instruction on how to orient the bushing to be able to move the front bushings away from the frame to get the top ball joints moving aft?

Yes, two kits, 4 bushings total. Follow THESE instructions:

 

[abodyjoe]

I think I will go for the moog kit. I see it comes with two bushings. Is that for one control arm so that I would need two kits?
Are there instruction on how to orient the bushing to be able to move the front bushings away from the frame to get the top ball joints moving aft?

you install opposite of the directions.

 

[72bluNblu]

Exactly what those guys said! Just don’t miss that the “front of car” arrow points down in that graphic.

 

[RustyRatRod]

I never look at those deestruckshuns, because for years they were misprinted. All I do is install the offset bushings so as to make the front of the control arm longer and the rear of the control arm shorter. That leans the top of the steering axis BACK to increase caster. That makes it easy to ME.

 

[Scottrico]

I never look at those deestruckshuns, because for years they were misprinted. All I do is install the offset bushings so as to make the front of the control arm longer and the rear of the control arm shorter. That leans the top of the steering axis BACK to increase caster. That makes it easy to ME.

Got it thanks for the info!
A bodies forum rocks!

 

[RustyRatRod]

Got it thanks for the info!
A bodies forum rocks!

We have our moments. LOL

 

[Kern Dog]

I agree… sometimes even fairly simple diagrams can be a bit hard to comprehend.
Robs way of describing the installation is unusual but accurate.
You country-folks are smart but do sound funny.

 

[RustyRatRod]

I agree… sometimes even fairly simple diagrams can be a bit hard to comprehend.
Robs way of describing the installation is unusual but accurate.
You country-folks are smart but do sound funny.

View attachment 1716119801

 

[junkyardhero]

RRR might maybe sound a little funny but for all intensive porpoises he's right.

 

[Scottrico]

Can I use one of those ball joint/u joint tools you can borrow from the auto parts store to press in and out the Moog UCA bushings? I used one recently to remove LCA bushings.
Or do I have to have the type like from Mancini racing? I imagine I could make the ball joint tool work, but have to create the correct size sleeve out of a piece of pipe from the hardware store. Do you have any recommendations?

 

[1973dust]

That's exactly what I used when I did mine. It was a set I already had from Harbor Freight.

 

[72bluNblu]

Can I use one of those ball joint/u joint tools you can borrow from the auto parts store to press in and out the Moog UCA bushings? I used one recently to remove LCA bushings.
Or do I have to have the type like from Mancini racing? I imagine I could make the ball joint tool work, but have to create the correct size sleeve out of a piece of pipe from the hardware store. Do you have any recommendations?

You can probably make one of the loaner tools work, but the UCA bushings are super easy with a homemade tool, you definitely don’t need the Mancini tools for them.

All you need is this…

The procedures is written up here for the UCA’s
Steering All Over the Place at 55mph+

 

[Scottrico]

Problem solved!
Thanks for the info.

 

[Scottrico]

Just read the instructions on installing the Hotchkis adjustable strut rods. It says, "Next rotate/thead the body in or out to the desired length. Shortening the strut rod can dial in more positive caster." Sounds good but how long to adjust the rod? I guess I will have to measure the old strut rod and go from there. I will be installing the Moog offset UCA bushings to get more positive caster. How much extra should I attempt with adjustment of the strut rods to move the LCA forward?

 

[S'cuder]

Just read the instructions on installing the Hotchkis adjustable strut rods. It says, "Next rotate/thead the body in or out to the desired length. Shortening the strut rod can dial in more positive caster." Sounds good but how long to adjust the rod? I guess I will have to measure the old strut rod and go from there. I will be installing the Moog offset UCA bushings to get more positive caster. How much extra should I attempt with adjustment of the strut rods to move the LCA forward?

I've read in this forum several times that you should adjust your strut rods to achieve zero binding, and that adjusting them to gain additional positive caster can cause binding. If the offset bushings give you less caster than desired, the best solution is to use aftermarket upper control arms. You can get adjustable or those with more caster built into the geometry.

 

[360notch]

I need some guidance on initial set up of front suspesion and wheel alignment on my 74 Duster. I am in the process of installing a completely new front suspension which includes a new Borgeson power steering box, pst 1.08 torsion bars, Dr Diff front disk brake kit, Dr Diff front suspension kit with stock type upper control arms, steering knucles, new upper and lower ball joints, idler arm, Pitman arm, tie rod ends, Hotchkis strut rods, etc. Only parts being reused are the center link and rebuilt lower control arms (pst kit).
I have read a lot of the posts concerning torsion bar installation and wheel alignment and am aware of many of the things to consider, but what concerns me is how will my front height adjustment be affected by the fact that I have installed the mancini racing leaf springs and the rear of the car sits up higher on the right rear side because of the different spring ratings. And how will wheel alignment be accomplished with this set up? This car will be driven on the street, and only go to the drag strip once or twice a year.

One thing that surprised me the first time I put in a Borgeson box, is that after setting the box to center, the pitman geometry was not parallel to the frame. I called Borgeson, and the guy said "Yes, that's because the Mopar box is adapted from the GM box, and to make it fit there is about a 5 degree offset in the mounting design'. He said it is very important to center the box, and he said that the tie rods will not be equal length when the box is centered. Also, in each install, the steering felt too sensitive, so I put in the a pump pressure reducing washer from the Borgeson kit.