rklessdriver

So the fastest stock IRS C4 Corvette is no longer going to race on on IRS. I have raced it on stock IRS for 2 years in heads up competition and honestly I have never been as competitive as I would like to be.

In 2013 the car would 60ft really well but I didn't have the HP to run on the big end.... only had a 600 hp pump gas 427 SBC.

In 2014 I built a new 722HP 434 SBC engine and the car would just go up on the bumper if I tried to get after it.... not to mention all the money I spent every 50-75 passes keeping SPICERs U Joint plant in business.

My best times on the factory IRS:

1.24 60ft (6.02@112MPH) - Old 427 on 150 shot

5.70@126 MPH 1/8 mile 1.36 60ft - New 434 on 200 shot

8.71@155 MPH 1/4 mile 1.36 60ft - New 434 on 200 shot

Alot of folks are going wonder why I built a 3 Link rear suspension and not a 4 link.... Well this is purely a product of the rules of the class that I race in. We are primarly a stock suspension class and 4 links are prohibited.

The class promoter evaluated the factory C4 IRS and how it is a 4 link, but he wouldn't allow me to keep it like that once I converted the car to a solid axle and anything I did had to bolt into the factory trailing arm mounting points. We stuck a compromise of me using either a 1982-2002 F Body TQ arm or a 2005-2013 Mustang 3 Link (also what was used under 1958-1964 GM X Frame cars) with a Panhard bar locator link.

The lower suspenion brackets "Bolt In" to the factory IRS trailing arm points. Of course the upper link crossmember had to be fabricated and triangulated to the frame for strength. There is an Auto-Fab Race Cars Pro Series anti-rol bar and also a fabricated coilover shock cross member installed to the factory frame rails.

All the suspension links are 1.5" OD .120 wall Chromoly with 3/4" Chromoly/Kevelar lined heim joints from Midwest Control Products Corp.

The rear end is a Quick Performance 82-92 F Body fabricated 9" Ford housing (62" wide axle flange to axle flange). It holds a Yukon alum Thru-Bolt center section with Motive 3.89 gears and Moser Engineering 35 spline spool/axles.

The rear brakes are Wilwood Dynapro low profiles due to the inner clearance issues associated with a Billet Specialties 15X10 wheel that has 6.5" back spacing. Also due to the fact that I still street drive the car alot, bigger brakes than those little solid rotor drag brake kits is helpful.

I picked the car up Sunday. I have some pics from before the package tray/deck/floor under the hatch was installed, so you can see the suspension.

Dominoc Cimino at Maryland Performance Specalties in Baltimore, MD did the fabrication. The man is one heck of a fabricator and chassis guy. He also built the Chromoly 8.50 certified cage for me that I posed pics of last year.











For those curious about the cost.... Little over $2000 in the 9" rear end itself. Another $4500 in labor to fabricate everything and supply some small parts - So about $6500.00 parts and labor. Of course you could use a less expensive 9" center section and axles to knock almost $1000 off that total.

I also went ahead and converted the car from the long standing TH350 transmission to a 2 speed Powerglide with a 1.80 ratio low gear from Transmission Specialties Inc. Hopefully this will calm the car down some on launch and allow me to get after the power harder.

New in the engine compartment for 2015 is a custom one off direct port fogger nitrous system from Nitrous Outlet. My 20yr old BG Nitrous Works plate kit was pretty much tapped out for power, even after Monte Smith tuned it up for me and I wanted to make the most of this new suspension... So I am making the most of the new rules. Limited to a 36 jet it will be somewhere around 400+HP all in.

There is still a little work and lots of pe-season testing to do before our first race on April 18. I am hoping, in legal trim, to be consistantly in the 5.20's 1/8th mile this season.

Feel free to show your support for my local heads up class and the people who support me racing in it. I am the lone Corvette in a class of Mustangs, Camaros and Novas.

MPC Real Street

https://www.facebook.com/MPCRealStreet

Maryland Performance Specialties

https://www.facebook.com/marylandperformancespecialties

My family's engine shop - Magic Racing Engines

https://www.facebook.com/Magicracingengines

Thanks for looking.
Will

bjankuski

That is nice!

mrmmoore

WVZR-1

Quite a "nice piece" Will - I've seen a few other construction efforts of that facility and I don't believe I've ever seen anything that was disappointing.

STEVEN13

Looks Great!

Not sure if I missed it-But what rear spring rate are you using?

I have my shocks/springs behind the axle also and I currently have 200lb springs. I may go softer and extend the shock travel.

Can't wait to see your results! Good luck.

Regards,
Steve

rklessdriver

130 lb spring rate. Still using the 6" stroke Koni double adjustable shocks. Of course with mine being a drag car all the springs do is hold the rear of the body up. It would have a higher spring rate if I were turning corners.

I'm excited to see how it will do as well. Serious changes from what I've been racing.
Will

383vett

Nice setup. Interesting the torque arm is on top. Can't wait to hear your crazy numbers.

l88rocket

From personal experience 3 links and drag racing don't seem to work, I would convert it to a 4 link myself, none the less nice looking piece

383vett

I've got a 3 link in mine. I don't have Wills horsepower and am running low 10's. My fabricator has built 7 second cars with a similar torque arm setup.

red L98

Looking forward to seeing this combo finally shine .. Not familiar with 3 link setup, Should be interesting. I honestly don't see any issues with today's power management options like progressive , MSD 7 etc.. The powerglide helps a ton , what rear gears are you running ? Not a fan of the 1.8 1st gear myself, although it's stronger than other options .

rklessdriver

I don't know what your experience is in regards to it but I been doing this a long time, and choose to do a 3 Link for a very good reason... in addition to the fact that 4 Links are outlawed in stock suspension class racing.

3 Links are working pretty good for these guys.... only the fastest Stock and Super Stockers in history...

http://www.fordracingparts.com/cobrajet/

We have a couple of customers racing these cars in NHRA and NMRA/NMCA. On small tires they tune, leave and drive every bit as good as a 4 Link car.

Will

rklessdriver

3.89 rear gear... Easy to adjust if needed.

I put a 1.80 low set in because its indestructible compared to the 1.69 and 1.58 low gear sets.

Plus my engine has a good wide and flat TQ curve. I feel it can pull the gear drop.... espc once I put that 36 jet to it....
Will

red L98

That's not bad starting line ratio .. I'm gonna end up with a 1.58 . 4.33 rear gears on a 28" tire .. Starting line ration is low and the RPM drop and tall gear should help pull the car.

Should run strong , good luck

blackozvet

Great stuff Will, i love seeing these sorts of mods being done,
its hard to believe you will be getting a full bodied c4 to go faster than 8.7, but it looks like you Will !

red L98

I wounder if you lost or gained weight with the swap .. Also any pics of the trans cross member ? Thanks

rklessdriver

I don't know about the weight.... The builder didn't weight it or set it up - like he said he was going to.

The trans crossmember is nothing special. It's just a bar that goes from the rocker bar across the floor infront of the seats and thru the side of the trans tunnel. It's 3 peices. It's got a flange on the other side of the trans tunnel for the center bar that has the trans mount.

I can take pics but it'll be a few days as I'm taking the car to my dads engine shop in GA tomorrow.

We were trying to get the car ready so I could run Nitrous X at the Ducks race in Valdosta GA on the 19th but it don't look like my nitrous kit is going to finished in time.

So if that dosen't happen, what I think I'm going to do is pull the engine out and check it over for GP. I only have about 50 or 60 passes on it last season and none of them were we even remotely leaning on it but since we have plenty of time, theres no reason not to make sure it's 100%..... Once I get my intake back with the new kit installed, I am going to re-dyno it.

Want to try out my my new carb.... A C&S Aerosol Billet 1000.

Want to try a few carb spacers now that I don't have that nitrous plate under there.

Also going to cut the headers off and shorten up the primary tubes. No idea why Stahl made them so long (34") to begin with.

Then I'm going to take it to a friends chassis shop (he's an oval track builder) and have him finish setting it up and get it scaled out. I have to add nearly 50lbs, even if there is no change lighter in weight from the 9" conversion... If the car is lighter now that's gonna get trickey becasue there arn't many places to hang weight bars on these things.

Once that is done we are going to test the car at Reynolds (Silver Dollar Dragway) to get it read for my season up here which starts April 18.

Will

tpi 421 vette

Looks good Will. You will like the dependability of a solid axle back there. A solid axle was the best thing I ever did for my car, for what I use it for.

rklessdriver

I hear you.

This cost a little bit to do but I wanted to do it right once and not have to worry about it for a long time. The stuff I have under there should be indestructible at my race weight and any forseeable future power level.

I'm looking forward to (really) launching this thing for the first time.

Thanks!
Willl

thetoy

I agree with Jim. I also run a three link setup in my car with a watts bar and in three years of hard racing I haven't touched the rear end once. I mostly autocross the car and I'll run the 1/4 mile track a couple times a year. I love not having to worry about breaking the rear end anymore.

_ski_dwn_it

Very nice progress...

I may have missed it, what heads are you running? Compression?

And what is the weight of your car?

Been thinking about nitrous also.....

And PS: you will love the solid rear. Wait till you take it down the track the first time and the car seems like it is on rails. Once you get power and start putting it through the IRS there is no comparison. IMHO - these cars should have had solid rears in them from the get-go! I have had several people buy mine and autocross/drag race and they love the solid rear in comparison. My car with the IRS when it was running low 10s always felts like it the rear was trying to walk around the front from side to side in an back and forth motion. I think it was just everything twisting and the torque from the 1/2 shafts working back and forth. With the solid rear at 9.80 and 1.26 60ft times, I could and do drive the car with one hand. With the IRS it was all hands on deck! And when the hands were not on the steering wheel they were on wrenches trying to fix it. Since I put my solid rear in back in 2006 I have not touched it since other than routine inspection. BEST THING I ever did to the car both track and street.