Mopar Action On-line – Tech Questions


Tech Question

Magnus Wallner, Stockholm, Sweden, 1972 Plymouth Cuda 340

I’m restoring and hopefully improving my 340 6pak ‘Cuda, and since it’s only gonna be a road car, I wanna improve handling as much as I can (afford). I have acquired everything that I need (I think) including one inch torsion bars, beefier front and rear sway bars, poly bushings, Koni shocks and MP rear heavy duty leaf springs. In addition to this I’ve also purchased subframe connectors and torque boxes from ART. I will alsoupgrade the front with 11/16″ C-body tie rod hardware. Most of my improvementsare, as you see, as per your recommendations. My question is:

How can I further improve the rear in a way that improves cornering? I’ve seen cars with Panhard rods but that don’t seem like the way to go since it pushes theaxle sideways. What about a watt-linkage (if that’s the English word)? Itshould be able to keep the axle in place without interference with spring travel.I have the 8 3/4 axle if it matters, 3,23 Sure Grip.

Best Regards from Sweden, Magnus Wallner


Actually, the early non-rubber-isolated, non-oval-bushing leaf rearsuspension setup, which your ‘Cuda should have (it was just being phased outon the luxo barges by this era) has very little of what we’ll refer to as”side sway”, as long as the U-bolts are torqued to factory specs (45-50ft./lbs). So torqued, the axle housing and front segments of the springsform a very rigid trailing arm, with some (much less effective) locatingbeing provided by the rear sections (which have the obvious shackles andlong length). So, in my experience, you really need do nothing. The frontspring segments are probably more rigid laterally than any of the new-designIRS stuff, especially when taken as a unit as described above.

I share your misgivings about Panhard rods, although Chrysler used thesuccessfully in the majority of the ’80s / early-90s FWD cars. The secret tominimizing the “side step” effect is to simply make the rod as long aspossible, pivot placement is also critical so the Panhard isn’t fighting thesprings.

The Watts linkage is excellent, having virtually zero functional drawbacks -i.e., not counting weight, complexity, and expense. But I think it would beoverkill. I say just replace all the rubber with urethane , if desired, or,at the front, even aluminum.

Now go humiliate a Swedish Ford or Chevy (Saab or Volvo) at the nextIke-parking-lot Auto-X, will ya?



Main Index | Current Issue | Tech Q & A | Tech Archive | Subscription | Advertisers Links | Contact Info