I have been putting together a suspension set up for my 70 using advice and tips from the track going guys on the board and a couple of friends who run vintage cars around Road America once in a while. I have had a couple of mild Pro touring rides that handled very well even compared with some modern cars. and of hoped I could come up with something similar without having to go to the XV level 1 or Hotchkis stuff..
Before I started the upgrades, everything on the car had been restored or rebuilt, so I think it was probably a good representation of a new stock car.
Bolt in sub frame connectors-
I got a pair of the dual tube floor hugging type from Magnum Force ($259).
I didn’t expect too much, and was more concerned about dealing with some of the sail panel cracking I was experiencing. Even though they are currently bolted in, they did make a big difference in the “solid feel” of the car. I still plan to weld them in later this summer.
Front sway bar-
The car came without a front or rear sway bar, and had .920 torsion bars. It handled like a cement truck. With the addition of the 1.125” front sway bar, the handling improved greatly. I tried using a G meter app on my iPhone, but couldn’t get data worth posting with my backyard methodology. The reduction in understeer was impressive. Now it handled more like a mid sized SUV, and didn’t threaten to scrape the gills off of the rocker panels on every tight corner.
Rear Sway bar-
I added a stock E body rear sway bar with poly bushings and end links. To be honest, there wasn’t too much difference compared to some of the other modifications. I do think the car felt more predictable in hard turns though.
Brakes-
I started out with stock 10 inch drums in the back and stock discs in the front. My backyard measuring tape 60-0 distance averaged out at right around 152 feet, with surprisingly little drama although I think the back brakes locked a little earlier than I expected when the weight shifted.
I did the 11.75 inch brake swap and used the following parts:
Brake Caliper - 78 Cordoba Slider type -$36 bucks at Advance Auto
Brake Caliper Support - 78 Cordoba Slider type -$100 bucks on EBay
Brake Discs - 11.75 inch 78 Cordoba Drilled and Slotted -$135 bucks on EBay
Brake Hose - 75 Dart -$32 bucks at Advance Auto
Brake Pads - 78 Cordoba semi metallic -$22 bucks at Advance Auto
In normal use, it was a little more positive when hard braking, but the improvement wasn’t too apparent until I did the 60-0 again and posted about 11 ft shorter distance. The fade resistance was another noticeable improvement, especially doing the repeated stopping tests. They seem pretty well matched to the stock rear 10 inch drums even without an adjustable proportioning valve.
NOTE- The new rotors were zinc washed and very shiny, but the area between the bearings still had a ton of casting sand in it. If this wasn’t cleaned out, the abrasive sand may have made it into my bearings and made for an interesting drive. I also installed new TIMKEN bearings and their races into the rotors. The bearing races that came with the rotors were zinc washed with everything else and I didn’t trust them.
Torsion Bars-
The car had a new set of Mopar Performance .920 bars on it. It wasn’t terrible, but I knew that more spring rate would help a lot. Just Suspension 1” torsion bars helped a lot. The ride didn’t seem to suffer at all, and the adjusters still let the car go low enough to rest on the bump stops if you want.
Shocks –
The car had a new set of Monroe gas charged shocks on it. I thought they were fine, but the difference that the Bilstein RCD shocks made on ride quality and handling was drastic. I was skeptical about a set of shocks being worth the $400, but I am a believer now. I think they handle much better than the old KYBs, and they ride as smooth as the Monroes.
Steering Box and fast ratio pitman and idler arm –
I installed a Firm Feel Stage 3 Power Steering box as well as the fast ratio pitman arm and idler arm. It may be the best modification I have made so far. It is actually a bit stiffer than I expected, but gives the car a much more modern feel.
NOTE- The fast ratio pitman arm also allows the wheels to turn in and out farther than stock, so now my 245/60/15 fronts will rub the frame rail if I turn the wheel the whole way.
All together as a package, these modifications made the car feel like a completely different vehicle. It is a pleasure to drive even on curvy roads now. With the stock upper control arms, I was able to get almost 4* caster at 0 camber. I have a set of Moog Offset upper control arm bushings that I might install to get even more. Modern 17” wheels and tires would make a big improvement too, but I don’t want to ruin the stock look of the car. If I had to pick just a few items from my list, I would do the frame connectors, the front sway bar and the Firm Feel steering box first, but skip the fast ratio idler arm. Next would be the 1” torsion bars and shocks and the rear bar. Unless I was going to run the car really hard I would consider the brakes optional because I didn’t really consider the stock set up that bad.
