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 also upgrade the front with 11/16″ C-body tie rod hardware. Most of my improvements are, 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 the axle sideways. What about a watt-linkage (if that’s the English word)? It should 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 rear suspension setup, which your ‘Cuda should have (it was just being phased out on 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 springs form a very rigid trailing arm, with some (much less effective) locating being provided by the rear sections (which have the obvious shackles and long length). So, in my experience, you really need do nothing. The front spring 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 the successfully in the majority of the ’80s / early-90s FWD cars. The secret to minimizing the “side step” effect is to simply make the rod as long as possible, pivot placement is also critical so the Panhard isn’t fighting the springs.
The Watts linkage is excellent, having virtually zero functional drawbacks -i.e., not counting weight, complexity, and expense. But I think it would be overkill. 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?