Any guidance on my 1970 Duster plans

poconos_power said
Hey everyone! I was recently lucky enough to pick up a 340 TA engine that has been off the road for about 40 years (going to need to get sent out, but it's complete). It belonged to my Dad's friend and his wife finally convinced him it would go better in a car than sitting in their garage. So I did what any reasonable person would, I bought a car to put it in. I ended up finding a 1970 Duster that was originally a slant 6 automatic. I got lucky the interior is great and it only needs small rust patches in the rear quarters, then I may send it out for paint.

In figuring out what I want this car to be, I have never done a performance build before, and was thinking autocross seems like something I want to do. Though I also want the car to be able to cruise and do road trips and such. So I'm looking for it to be good at multiple things but not great at one thing I suppose, I'm sure my limitation will be my driving skill instead of the car in the beginning, I'm just something that works and lets me get into it and would be an interesting project to get to my goal. I did some research and there are plenty of great options for full coil over conversions on the front, and I'm sure I could do that eventually, but I find the prospect of trying to tune in a t-bar suspension more interesting. I figure I can always upgrade and change in the future. So after a few weeks of lurking and reading here is what I'm thinking, and please let me know what you think about this.

For the rear, I was able to score a new 8.75 rear at Carlisle this past summer to upgrade the previous rear. I was thinking of putting in the Hotchkis geometry corrected leafs.

For the front, I was going to do the Firm Feel reinforcement kit for the k-member, reinforce the lower control arms, get the Firm Feel tubular uppers with the big ball joint (if I replace the spindles), and adjustable strut rods. Poly bushings for everything. Also the car has a pretty big front sway bar currently, though I haven't measured it, but I don't think it's original.

For torsion bars I was thinking 1.08 or 1.12 based on what I'm reading here. However the question is, how do I address the 1" drop from the Hotchkis leafs? Do I get drop spindles or just drop the front using the torsion bars?

And finally I'll replace the power steering box with a better ratio. Perhaps at some point I'll also add frame rail connectors and torque boxes, but I'd like to get driving down the road first at least.

Any thoughts out there about this? I've read a lot of posts saying if you set up a torsion bar suspension correctly, it can be on par with a coil spring setup, but I haven't found the full breakdown or how that can be achieved. This is what I've pieced together from various posts. Thanks!

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Looks like a nice car to start with. I became addicted to autocross almost 4 years ago. Don't worry about being the fastest out there, because chances are you never will be. You will, however, have the coolest car there! I wouldn't worry about the ride being too harsh if you go with large torsion bars. It's all about the shock you use to control the big bar. That's the beauty of pro-touring cars, they can handle on the autocross and drive to and from the event with a perfectly comfortable ride. The same can't be said for the guys that go "street/strip". So many people buy into the Super stock springs or caltracs and use drag racing shocks when in reality they never go to the track. I've had that setup, it rides like a tank. No thanks!.
Others have done a good job explaining what parts work well, so I won't go into that. I've run the torsion bar recipe outlined here and it works very well on the autocross. (I have an HDK coil over setup now) Maybe not mentioned here is the importance of alignment. You will want at least 6.5+ of caster and maybe .5 of camber to start. If you decide to do more autocross, you will likely want to bump up the camber. It's been very surprising to me how much difference an alignment can make. Here's a photo of my car. Notice the front tires are nearly vertical, particularly the one outside front and the inside tire still has good contact with the ground.

This is an extreme circumstance, but I wanted you to see what a standard alignment looks like.