Is there a kit to convert the C4 from IRS to a Ford 9" or will it all have to be a custom build?

 

It will have to be custom build. I know of two people who have put a solid axle in theirs and they both had to do some hacking to get it in.

 

IF YOUR CORVETTE IS A 94 OR NEWER ITS NOT AS BAD BECAUSE THAT YEAR FORWARD HAS A FRAME TO ATTACH THE CLIP TO.

 

The one I'm considering do it to is an 89.
What are the rules for how fast you can run at the track and still use the IRS? I see a lot of people running 9s and 10s with them. I also know 2 people that ran 10s and 11s at Gaineville Fl and were told that they had to go to a straight axle.

 

The NHRA RULE BOOK calls for drive shaft loops at 12.99 thats about all.to turn 10s 11s 12s you also need a 6 point roll bar, 5 point harness that is only good for about 3 years.

 

Actually NHRA factors the C4's IRS differently than they do the earlier IRS suspensions. I spoke at length a couple of years ago with Wesley Roberson (the head NHRA tech) when I broke into the 9's with mine. They are a "positive retention" setup unlike the previous IRS's which means the wheel won't come off should you break a halfshaft.

Regarding a 4-link or ladder bar setup for a solid axle swap it's really NOT that difficult but you do have to cut up the car from the rear bulkhead (behind the seats) back. I don't know what is meant by the '94 ups having a frame to attach it to but ALL Vettes have a real full frame (unlike unibody cars) and I don't believe the frame was changed at all between 1984 and 1996. You simply have to weld a ladder bar or 4-link crossmember to the frame and a secondary member for the coil over shocks that will be required. I've looked at several converted solid axle setups; one of which is Bob Curran's PRO Xtreme Street "Skunk" which is a ladder bar car. Believe it or not but it's NOT that difficult, it's just most people don't wanna cut out the rear floor of the car to do it.

I've been working with my chassis builder on coming up with a solution that would allow the stock control arm forward mounting locations to be used and the axle brackets to be on the rear of the axle instead of the front like a typical convention 4-link is. That would give you longer length bars and establish the instant center where it needs to be.
-Jeb

 

Thanks Jeb for the reply. Does this mean that the C4 IRS is okay for the 9s? I may try to do the 9" myself one of these days.

 

According to Wesley they don't have a factored ET for the C4's... The ET for the earlier IRS Vettes is 10.99 before a rear end swap becomes necessary. I've run 9.90's at several NHRA sanctioned tracks in my car (mostly Memphis) and never had anything said to me about the rear.. My 6 pt. cage was a different story... As soon as I broke into the 9's they told me I had to add a halo bar and downbars...
-Jeb