I am back to working on my brother's 74 Duster. I have a question about upgrading the front and rear suspension.

This car will be a daily driver in and around Seattle. It will be 225 powered with AC, and have an 8 1/4 rear axle with 3.2 rear gears. I have rebuilt the front suspension to stock specifications using Moog rubber bushings, but NOT the problem solver offset bushings. The rear suspension is still the stock 3.5 leaf springs that look OK for now, but I want to replace them. It has power steering. The brakes have been upgraded to discs in front an 11 inch drums in back (yes, 11 inch). Rims are at least 15x7 on all corners.

I would like to upgrade the front and rear suspension for better handling and comfort. I am not adverse to changing the alignment specifications to achieve superior handling. However, since I just put the new front suspension back together I don't want to rip it apart to install offset UCA bushings.

So, what I am looking for is a recommendation and source for:

(1) thickness of new front torsion bars
(2) rear leaf springs (JC Whitney five leafs OK?)
(3) front alignment specs?
(4) anything else I have overlooked?

I have a very limited grasp of alignment theory and application. All I know how to do is replace stock parts. I will probably upgrade to the C body adjuster sleeves when I have the shop do the tie rod ends. I am just looking for a good package recommendation for a daily driver, not a rally racer.

Thanks!

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Casually looking for a Clifford hyperpak intake for cheap.

(1) thickness of new front torsion bars

I really like the 1.000 inch bars that are widely available. I had the NLA .980s on my dart years ago with urethane bushings, and now I have Just Suspension 1.000 with rubber on the Valiant and I really like it. I think it's my new favorite. But I do need more caster (did not use problem solver bushings). Don't worry about ride - it's nowhere as stiff as your average new car with 18-inch wheels.

(2) rear leaf springs (JC Whitney five leafs OK?)

I have used only sagged stock ones. But I think the MP 1-inch arch oval track springs with the special longer front hangers are what I am going to use next. They are cheap.

(3) front alignment specs?

More caster! I have mine at 3.5 now, I just told the alignment guy to give me 1 degree caster, 1/8 toe-in and as much caster as he could. I wish I had more, like 5-6 degrees.

(4) anything else I have overlooked?

Swaybars, front in particular. For a street car a rear bar is nice if you have soft springs; if you swap to heavier springs you might not need it.

Also good shocks. I have Edelbrock but I don't think they are made anymore.

I had c-body adjusters on my Dart and honestly I can't tell the difference. If your linkage is tight you'll be fine. It would help more with stickier tires, i.e. nothing that would easily fit under an A-body.

Thanks for the input. After looking around at the prices of new leaf spring packs, I am probably going to attempt to keep the original four spring pack and add a leaf out of a set of springs I removed from my brother's 83 Dodge 1/2 ton van. I measured and the leaves are the same width and I am fairly certain the the longest spring from the van pack will fit between the longest two Duster leaves. Fingers crossed. Now I just need to find a pair of bolts to hold the spring packs together.

I am definitely going to be getting a front sway bar, too.

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Casually looking for a Clifford hyperpak intake for cheap.

I actually have had pretty good luck with stock rear springs (the 5-leaf variety) and an addco 3/4 swaybar. I've used the same setup on two different cars now and it works pretty good. I even like the sag because it sets the rear ride height low to match a lowered front.

For the street a soft-spring/big-bar setup is more predictable and better over bumpy roads than a stiff-spring/no bar setup. The latter is in theory better for racing because leaf springs have plenty of inherent roll resistance and a swaybar technically lowers rear grip. But I (and your bro likely) don't race, so the difference in when you can put the power on exiting a corner is not so important.

Thanks. I got the van spring packs apart and I thin I can reuse the clamp bolt from the van springs on the Duster springs andI am about 90% certain the second longest van leaf will fit in between the two longest Duster springs. Near as I can tell, the Duster spring are rated to carry 500-600 pounds and the van springs are rated to carry 1600-1800 pounds. I am hoping that adding a single leaf from the van springs will stiffen up the rear Duster springs enough to be acceptable.

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Casually looking for a Clifford hyperpak intake for cheap.

If new rear springs are a budget buster I don't think you want my opinion on shocks and torsion bars. I liked my 1.04" torsion bars and QA1 shocks on my '67, but those shocks are $146 each.

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Joshua

New rear springs are a budget buster right now. I am looking at replacing the gas tank, replacing the rear springs, and getting a new gearset installed in the rear axle in the near future. I am trying the van leaf adding route simply because I have the van leaf springs on hand and it will cost me nothing but time to try it out. If it doesn't work then I will be ordering new springs.

I am looking for what parts I should put on my want list and start saving up for. I can save up for shocks and torsion bars and a front sway bar since I won't be needing to buy those in the near term. Right now the Duster has NO shocks since the original shocks were compressed to be pushed out of the way for the disc brake and rear axle swap about three years ago and have remained compressed to this day.

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Casually looking for a Clifford hyperpak intake for cheap.

Front and Rear sway-bars with poly bushings.

3/4 rear
1 1/8 front

Addco is fine if you improve the front mounting (I have a post somewhere on the site on how to make it better)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

If you are doing bushings, change the tie rods to the C-body 11/16" rods, they will firm up the steering (or show you that the box is really crappy).

-D.Idiot

I've always been a fan of using the stock T bars and a fat sway bar. Nice ride in a line, but a big front/rear bar to firm up the handling. I don't like my fillings falling out driving down the road.

The stock bars on a 60s-70s mopar are so soft that they allow too much suspension movement when you get on the brakes and accelerate even if you have a huge swaybar. On the street that makes handling in an emergency braking situation very unpredictable.

And, in a bumpy corner you run out of suspension travel and hit the bumpstops which sends the spring rate to infinity and results in instant understeer. This happens even on the street, and if you lower the car at all you make it worse.

These suspensions were designed around narrow bias-ply tires with stiff sidewalls. The effective wheel rate of a 60s Mopar is approximately 1/3 that of any modern car of similar weight and power (70-ish versus 200+).

Put 15-inch radials on it and you have added 2x more grip and a softer ride. That means 2x the cornering force and 2x the braking force that the original suspension was meant for, and 2x the suspension movement. You have to increase the t-bar diameter just to end up where you started!

I installed stock V8 torsion bars and new stock rear springs on my '64 225 convertible, and I love how it rides and handles. I didn't want the harshness of poly anything, so I rebuilt with all new US made suspension and steering parts. The only real mod was a first stage firmfeel box, and it was worth the money.
I also upgraded tires and wheels to stock 14" specs, and replaced the shocks with standard Monroes.

I don't street race and TX roads are in bad shape, but I don't baby it, and I'm never left unsure of what the car is doing.

When all the parts are new, the old A-bodies handle very well when equipped with a sensible selection of stock parts. The only future modification I intend to try is a better shock, since at slow speeds I experience some annoying chassis related shudder.

I read thru this with the same question on the rear leafs and didn't see an answer that fits my situation. I hope you guys are still following this one. Before reading this there was a post saying to use the four leaf set up and not the five leaf, but no cap or rates were stated. So I set out to buy and all General Spring had was 5 or 6 leafs. So I just replaced the leafs on my 72 225 Scamp with General Spring KCs #78-705 which is a 5 leaf 620 lb capacity 85 rate set up and I can't tell any difference from the 40 year old factory leafs. I also need to change out the leafs on my '64 convertible valiant and am wondering what to do next. General has a #33-909 6 leaf 640 lb cap and 120 rate that I could use on the heavier '72 and move the new 5 leafs onto the '64. They also have a #78-581 6 leaf for the 383ci that is 760 lb cap 130 rate I could do the same swap on. Or I could use the #33-909 on the '64 and slap some old leafs in the 5 leaf set up presently on the '72 making them a 6 leaf set up.
Thoughts?

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'64 Valiant Conv V8
'72 Scamp /6 4bbl
'79 Adventurer SE

Well, the only progress I have made with this is to confirm that the longest non-eyed leaf out of a 83 Dodge B-150 rear leaf spring pack will just barely fit in between the longest and second longest leaves on an A-body suspension. I have the van spring packs apart and the wheels off the Duster but that was as far as I got before I but my right hand and had to get stitches. I will get back to the suspension project at a future date.

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Casually looking for a Clifford hyperpak intake for cheap.