I have an old '80 vette that I plan-on turning-into a strip-only car.

My original plans were for a complete 'back-half' (narrowed 9", new frame rails, wheels tubs, 33" x 15 slicks, ladder-bar/4-linkwith coil-overs, fuel cell, cage, interior tin-work, etc.), but the cost of that, coupled with a new motor is

making this a very long-term goal, at-best.



A few days ago, a buddy said:
"Why not take the original 10-bolt rear-end from your '79 Z28 (I replaced it with a bullet-proof 12-bolt years ago), that already has a posi 4.56s, whack all the mounting tabs off it, have the local chassis-guy build you a 4-link/coil-over suspension using it (the 10-bolt) and the existing frame rails, fuel tank, etc., and while he's at it, have him install a decent cage, too.

I got enough spare parts (block, crank, rod/piston assemblies, cam, cylinder heads, intake, etc.) laying around my shop that we can put a 400+ HP 355" SBC together for cheap;
it'll make as-much, if not more, HP than the one in your Z28 (which runs high-12s), run on pump-gas, turn easily to 6400 RPM, and won't hurt itself in the process.

You've already got a spare THM400 that is 'built', ready-to-go, along with an 8"/4000 RPM stall converter.

You don't want to try changing the Earth's rotation; you just want to run good, consistent mid/low 12s without busting the I.R.S., and without spinning the tires.
Figure-out what wheel-offset you'd need, using the stock-width '79 Z28 housing, to get 30" x 10.5" slicks (13.5" section-width) into the wheel-openings, without rubbing the inner wheel-tub....."

Originally, I thought: "No; I want a REAL race-car", but it did get me thinking about this possibility.


I guess my questions to you guys with very big rear tires are:
#1: What are the dimensions, in inches, of your tires (anybody running 30" tall Pro-Street-style tires?) Height, width, section-width, etc.
#2: What is the side-to-side dimension of the stock I.R.S. (wheel-mounting surface to wheel-mounting surface)?
I am going to my storage facility later today to measure this dimension on the 10-bolt...
#3: What wheel-offset/back-spacing would I need to stuff 30" x 10.5" tires, with a 13.5" section-width (cross-section) tire into a C3, if the trailing-arms and other I.R.S.-bracketry weren't a factor?
#4: Any 'other' questions I've over-looked?

My 'original', whole-hog plan would've cost close to $10k at the chassis-shop, and another $5-$7k for the motor;
my buddy is thinking that this 'modified' solution would cost only $4k at the chassis shop, probably another $1k in wheel and tires (both front & rear), and maybe as little as $2500 in the SBC.

In other words, "IF" this works, I can go racing for half of my 'original' plan...

THANKS IN ADVANCE:
any thoughts, ideas, and recommendations are greatly appreciated.

 

I dont know about putting in 30 inch tall slicks, but i was able to fit in 17 by 12 tires with vbps three inch adapters to get me the proper backspacing, im not sure how safe it would be to drag race with wheel adapters though.

 

Alot of people have said that 30 inch slicks were too tall. When you launch the car will squat and the tires will hit the rear fenders which will either crack them or tear them off. I suppose you could raise your rear end a few inches if you wanted to run the 30s. With offset trailing arms, I think the widest tires you can run without flares are 315s with 5 inch backspacing. Mounting surface to mounting surface is somewhere around 59 inches, I will look in the aim and online for a more exact figure. If all you want to run are 12s, then you can get away with keeping your IRS and just replace a few things to make it stronger and more consistant. People are running low 9s with the stock style IRS after spending a few grand on stronger components.

 

Vetteman9369 informed me that running the I.R.S. isn't too bad, but the '80 came with the weaker aluminum Dana-44 rear-end.
Opting for TOM'S 12-bolt set-up was considered, but I'd still have all the splined joints, alignment issues, U-joints, geometry-problems, etc.
I'm guessing that I'd need to find an 'early' C3 iron rear-end ('pre-80), and then spend a few grand...
and at the end of the day, I'd still have a rear-end that is made for cornering, not transferring power in a straight-line.

This Vette'll never see the road again;
it is 'well-used', and I bought it specifically for this application.
This'll become my 'primary'-car at the track, 'specially if/when I relocate to compete in the various 'Corvette Challenge Series'.

Raising the rear of the car is not a problem for clearence:
Vetteman9369 says he thinks I can run 30" x 10.5" in an I.R.S. with proper offset trailing-arms/wheel back-spacing.
Besides, I'm not sure how much it'll 'squat' with the 4-link/coil-over suspension.
If 30" x 10.5" will 'clear' everything in an I.R.S. application, unless I'm worng (or, 'wronger-than-usual')the only way it won't work with a solid-axle rear is if I can't get wheels with correct back-spacing to fit with the 10-bolt Z28 rear end, centering the tires in the available 'space'.....

 

As best as I could measure (without using straight-edges), the OEM '79 Z28 10-bolt looks to be 61.5" mounting-surface to mounting-surface.....

Anybody?