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.
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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.
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