<VV> Re: VirtualVairs Digest, Vol 7, Issue 28

[Padgett]

>but here's a review of "Corvair Tire Size 101".

That assumes you want to keep the same "revs per mile". One of the greatest 
factors in the modern engines ability to go 200,000 miles without an 
overhaul (and much better gas milage) is much lower gearing in cruise. 
Consider my '92 Pontiac TranSport trip car. 3800 engine, 3500 lb curb 
weight, 24.7 mpg on my last 500 mile trip to Naples.

Good piece of that is a gearing combination that turns under 2000 rpm at 70 
mph.

If you consider that the engine is a big air pump with lotsa reciprocating 
masses (get stopped and reaccelerated twice per rev), at 70 mph with a 3.55 
and 1:1 final the power required just to turn the fan is about the same as 
to move the car on level ground (see the 140 stock engine test).

Many years ago (first fuel crisis) I was able to coax over 25 mpg @ 70 
(pre-55) from a 67 Camaro convert with a 327 mainly through FI and 28" rear 
tires. Then it was not politically correct (future as evidenced by the GMI 
Firebirds was an I-6 with turbo and massive thermal wrapping, I have never 
thought much of boosted engines myself).

However I strongly suspect that if you could gear/tire a Corvair to under 
2500 rpm at 70 mph, mpg would go up and engine temps would go down. 
Significantly.

Given that the stock tire is about 24 " tall and the 255x70x15s on the back 
of the Judge are more like 29" (make the 15x8 Snowflakes look small & would 
effectively change a 3.55 to a 2.93)  Might be interesting to see if they 
would fit on the back for a test.

Of course when autocrossing seriously I never had just one set of tires and 
the auto-x tires were much shorter than the street wheels and tires.

ANFSCD: Did anyone ever make a lock-up torque converter that would fit a 
Covair PG ? Am sure is much looser than a modern automatic.

Padgett