Re: Project 69 Corvette L88
 

Before you finalize your decision on the rear end please contact other Big Block Corvette racers that have successfully used an upgraded I.R.S. I have made an
Aluminum 12 bolt I.R.S. casting called the HammerHead for the 2010 Camaro that has been in several test cars with 800 plus hp. I am currently in the process of doing the same for the Challenger, Viper and C4 Corvette I.R.S.

If there is enough interest I can make a cast iron version of the 12 bolt HammerHead for the 63-79 Corvette also. NHRA will not allow an Aluminum replacement differential casting. If you are curious please visit hammerhousing.com for more info. Thank you
Fred Lee 231-740-5534 Cell phone

Re: Project 69 Corvette L88
 

Hi
Looks like a great pce.
I may be wrong but it has been my thoughts and understanding that the IRS may use up some hp and with my build of course I am only looking at point a to b in a straight line no corners, having said that thou may be there is a advantage to IRS on a rougher or uneven tracks ?

Are any of your units being used in the copo's in stock eliminator ?
I thought the factory ones came with a 9 inch ? Unless somebody was scratch building one
What are you thoughts on the hp drain from straight tube to IRS

Thanks Rory

Re: Project 69 Corvette L88
 

Rory,
All COPO Camaros and DragPak Challengers do use Strange engineered and NHRA
accepted 9 inch Ford straight axles similar to the Cobra Jet Mustangs. The 12 bolt
HammerHead I.R.S. that I make will be legal in Gen 5 Camaros that are in the NHRA
stock car classification guide but it is not used under any COPO Camaros.

Big Block Corvettes were known for breaking the weak factory I.R.S. rear ends but Tom's Differentials has developed many parts that will last. My goal was to make a 12 bolt aftermarket casting that will accept the 9310 alloy gears in all the popular ratios, 35 or 40 spline spools and whatever other heavy duty driveline parts that are currently available.

I have not tested the power loss between a "straight axle" and an I.R.S. but the first test car for my 12 bolt I.R.S. was also the first test car for the Driveshaft Shop's 9 inch
Ford fabricated I.R.S. We used a chassis dyno to compare the power loss at the rear
wheels. The horsepower numbers were 780 for the 9 inch Ford and 800 for my 12 bolt.

It has always been rumored that 12 bolt made 3% more power than the 9 inch Ford
because the pinion is 3/4 of an inch further away from the ring gear centerline than the
12 bolt. (1.50 vs 2.25 inch) I do remember seeing 12 bolts installed under SSA/A Hemi cars to replace the Dana 60 also. Fred Lee

Re: Project 69 Corvette L88
 

Fred, what is the website again? www.hammerhousing.com doesnt seem to be working for me. need challenger info

Re: Project 69 Corvette L88
 

I am sorry. The website is hammerheadhousing.com
The part is named and Trademarked for the shape of the Gen 5 Camaro front mount. Fred Lee

Re: Project 69 Corvette L88
 

Hi Fred
Yes I could see where there would be a market for it for sure we have worked and built a few corvettes for customers that where street strip cars and they did not want to loose the IRS but needed things made stronger so the centre section that you are proposing for the corvette I would think could have a pretty decent market.
What would a set up like that be worth ?
Thanks Rory

Re: Project 69 Corvette L88
 

Rory, if our Tom's differentials IRS I using up any horsepower, it doesn't seem to show it in 60' or in mph. The 3x2 combo is a little soft across the middle, but the mph is all there. Last week in bowling green we were consistent 1.42x 60' with the rear wheels. The car hadnt been to the track in almost three years, so it was a little slower than it should have been, but a 10.53@129.77 doesn't look like the IRS is eating too much hp.

Re: Project 69 Corvette L88
 

Rory,
I was a Patternmaker for the foundry business for 40 years, so I am responsible for idea, design and manufacturing of the actual casting only. The price on my machined casting of about $1200. - $1500. is based on the low volume early Corvette market.

The entire bolt-in kit requires Aftermarket stub axles, half shafts, etc. which will need to be purchased from a specialty company like Tom's Differentials. In the case of the Gen 5 Camaro 12 bolt kit, The Driveshaft Shop in Salisbury, NC makes those parts for the kit which retails for $5495. with driveshaft, stub axles, outer CV axles and choice of gears. Fred Lee

Re: Project 69 Corvette L88
 

Thanks Chad
That gives me more information to go by as I don't know many running the IRS in this situation so I don't have much to go by or compare to.


Hey Fred

Thanks for the information and input sure sounds like a great pce. And gives me more to think about , I have started somewhat on my straight axle with pces. Etc but could go either way just yet.
Thanks again Rory

Re: Project 69 Corvette L88
 

Rory call Mike Dyer at 214-717-8379 he builds the tom's 12 bolt IRS for c2-c3 corvettes he's very knowledgable and does great work.

Tell him Richard Mynatt recommended him.:)