mjb%hoosier@cs.utah.edu (Mark Bradakis) (02/01/90)
Gee, wanna buy a nice white 67 solid axle? Have I got a deal for you... As one who's been flogging TR4s around parking lots for a couple of seasons now, thought I'd throw in my opnions. The short answer as to which type to get is it doesn't really matter. If you end up really liking the car and doing well and spending some time and money on it, the IRS car might be a bit better. But for the first 99% of the car's potential the two are fairly similar. In other words, don't pass up a solid axle car in good shape just because it isn't IRS. The most important consideration is to get a 4A which is in good shape. The condition of the car is more important than the suspension in the beginning. Being a flexible car the sills (rockers) need to be in good condition to provide as much rigidity as possible. Get a car as clean and rust free as you can afford. Also, if you want to race you should get a 4A and not a 4. The 4A has a much improved frame. It is possible to actually set the front suspension to reasonable settings (see below) without using large heavy impact instruments as on the 4. The 4A also has a very good stock cast iron manifold, flows much better than the 4's. As a matter of fact in the next day or two I need to weld up a collector to convert my car from the front muffler/rear muffler set up to just having a 2" pipe running to a rear muffler. On the 4 I raced, I had Quicktrip headers and a 2.25" pipe ending in a turbo tube and then Supertrapp. Noisy, good flow but the lower end torque seemed a bit off, and that is more important on an autocross car than top end. Another advantage of the 4A suspension is that is the same as the TR6, so one can easily adapt TR6 front sway bars to the car. I run a 7/8" custom made bar on the front, will put a small one on the rear this year. Also various TR6 springs are available which fit right in. I am assuming that you'd race the car in Street Prepared, in case you can't tell from what I am recommending. The solid axle car has a lot of unsprung weight back there. The wheels, tires, shocks, springs, etc. on the Rust Rocket were about 300 pounds or so, nearly 15% of the car. That was the unsprung portion. On the IRS cars I imagine [never having weighed the parts] the unsprung rear weight is probably more like 120 pounds, around 5% of the total weight. While one would think that the IRS would be much better, the limited range of travel and angle of the swing arms isn't that great. Lots of folks in the motoring press of the time seem to say the IRS isn't that great of an improvement. One fellow I respect says the solid axle actually is a better handling car. I'd like to take two equally prepared cars, one solid, and one IRS, and try them side by side. Oh well, maybe someday. At any rate, the IRS car, from what I hear, has to be sprung really stiffly in the back to handle quick transitions very well. I wonder how stiff Randy Lewis' TR6 is? He had the rear in the air at Salina, I couldn't jounce it and see. I myself ran the stock leafs on my car last year, and plan on going a bit stiffer this season, maybe tube shock conversions if I can afford it. Oh well, enough rambling for now, let me know how it goes, I'd be glad to offer advice, parts suppliers, etc. mjb. ---- Appendix 1: My white autocrosser: (may be off, from memory) 67 TR4A, SCCA DSP 87mm bore kit (about 2180 cc) 10.3 or so compression (neve did cc the heads) 2 42 DCOE Webers planned, ran 40s last year. The 40s had 30mm chokes, 115 mains, 140/f? idles, 190 airs. Maybe f15 e tubes? The 42s will have 32mm chokes, we'll see about the jetting, depends on exhaust I end up using. Remember I'm at 5,000 feet elevation, need leaner fuel jets. Offhand I would say the motor is developing maybe 110 bhp. I WILL dyno it this year! Front suspension: SAH springs, Koni shocks (set full soft), 7/8" sway bar toe 1/32" in, 1 degree neg. camber, I think about 4.5 degrees castor All new Delrin bushings, new trunnions, ball joints, etc. Poly steering rack mounts. Rear suspension: Dead stock, really needs to be stiffend up to match front end. Plan on new springs and shocks, small sway bar. 15x7 alloy wheels, 195/50-15 General tires, may go to 8.5" rims with Hoosier 225/45-15 later this season, hopefully by the Utah divisional. The car is now up on stands in the garage getting the gearbox rebuilt, new clutch, and the rear axle rebuilt with 4.1 gears and a limited slip. Also a GOOD roll bar is on order, I'm going to move the battery, etc.