G-Body IRS options

[2wolf_Michael]

I am thinking about replacing the solid rear axle with an IRS set-up for my 88 Monte SS. I am looking at a few center section options. My big concern or issue is figuring out is the uprights to use.

I am figuring either C5 or C6 options isa start, but have also seen custom options on other websites.

My question is for both track and street use what would be a good starting point on a design.

If it helps, I am planning on upgrading the front suspension to C6 based set-up.




I am working on a few drawings for ideas, will post them as soon as I can.

[2wolf_Michael]

I have a few drawings for a Speedway Eng Stock Car QC center section set up for IRS use. The brackets or replaceable, as I only added them in my drawing to give an idea for mounting.


I have a line on a used center section and a rebuild kit. I would only have to pick up the proper side bells and stub axles. I also still have the factory rear axle and a 9" sitting in my shop, which I could modify to use also.

I figure the QC rear end would work best for a custom build up and would allow for quick gear changes if needed.

Looking for opinions or idea????

[silvermonte]

Im not going to be able to help you with any answers, but im along for the ride to see how you do this. I cant think any g-body that has done this yet.

[2wolf_Michael]

Thanks Miles.

I with myself having a Aerocoupe model, I am hoping this will give me a little extra space because of the extended package tray. This should help hide things better, without having as many issues with the body. not sure if it will work out that way though.

If I can do this right an IRS set-up should not take up much more room that the stock set-up.

I will be adding to the drawing shortly.

[silvermonte]

I would think that once you figure out what center section you want to use and then get it mocked up in the place the rest of the puzzle pieces should fall into place pretty easy. With seeing people put 3 and 4 links in without much floor mods i cant really see where this would be much different, maybe at the front of the rear wheel wells where the links would hook to the frame, thats about all i can think of that would require some cutting.

[2wolf_Michael]

Yes, the Qc center section is only 17" wide from CV flange to flange, but is 24" deep from u-joint flange to the back of the stock style rear cover. So this takes up extra space and it is not really centered in length 10.5" from axle centerline to u-joint flange face.

I am doing my drawings based on running 335/30R-18 BFG rivals as those are the dimensions I have, at a near factory track width.

I hope to have a basic drawing up posted up tomorrow night for a starting point, only issue is I do not have a C6 spindle to use for dimensions right now, which may change some things later.

[Schwartz Performance]

Are you using the stock frame or building one? We offer a chassis for these cars, we could leave the rear end out so you can fab in an IRS. As you know, the stock frame is very weak and heavy in the wrong areas.

The QC IRS looks pretty sweet though, interested to see it all executed!

-Dale

[Rwolf15241]

you could use a ford 9 inch!! or a Mark VII 8.8 center

[Marcus SC&C]

Picking which center section and spindles to use is the least of your worries. Throwing some parts together street rod style (looks cool don`t it?) isn`t super hard but making it perform really well IS. At what height do you want your roll center? Why? How much lateral roll center migration is acceptable? Why? How much camber gain do you want? Why? How much will toe in increase under heavy acceleration? Why? What`s the ideal anti squat for an IRS in a G body? Why? Does a C6 share the same geometry requirements as a G Body? Why not? Etc. etc. Once you`ve answered all of those questions and measure the frame (or design a new one) then you can start looking at the right parts to fit the bill. I`ve done a few scratch built suspensions with IRS like this one http://scarab-motorsports.com/model.php which have had quite a few class wins and a few conversions, it`s nowhere near as easy as it looks to do it well. They`re cool looking but in my experience the view is seldom worth the climb.

[Samckitt]

I am thinking about replacing the solid rear axle with an IRS set-up for my 88 Monte SS. I am looking at a few center section options. My big concern or issue is figuring out is the uprights to use.

I am figuring either C5 or C6 options isa start, but have also seen custom options on other websites.

My question is for both track and street use what would be a good starting point on a design.

If it helps, I am planning on upgrading the front suspension to C6 based set-up.


I am working on a few drawings for ideas, will post them as soon as I can.

I know, old post, just wondering what came of this if anything.

[Vimes]

This should give you an idea of what you'd be in for on it. This is my project, which is using a 2003 Corvette IRS with a 2013 Camaro IRS differential. The shop still has some reinforcing work to do, and there are more pics in my project thread in the signature. I'll have to have axles made up to fit, but as I'm going stock Corvette width that's something available from G-Force. My project will top out at 600HP tops so the stock Camaro diff will work, but G-Force also sells these huge, chunky Camaro IRS units based off a Ford 9 inch that will handle pretty much anything you care to throw at it.

There's several ways you can do this. There's Dobberton adapters, which I don't really recommend but can sell you an unused set. They're designed for someone who can do minimal welding and require 2x4 steel rails to mount to but require no dimensional measurements past that. You can also weld tabs on like the shop I used did and use the factory cradle. You can also just get the upper and lower A arms, and brace the framerails with tubing that also supports th IRS. Don't ask for measurements, that truck is at the shop doing my frame and it's a good 3 hours away, but if you can get under a Corvette or access a factory body manual all the measurements would be there.

I'd suggest going with a C6 over a C5 as the peanut gallery says the C6 is a better handler. If you stay with the stock Corvette width you have the option of using the leaf spring, if you narrow or widen the leaf is out and you must go coilovers. Another alternative, some of the big Ford cars also had IRS, and are designed for a car the same size/weight as a G-body. An early 90s Cougar/Thunderbird was a comparable car to the G-bodies and, as a former owner I can attest that they handled great for a big boat.

Also, measure the A arms because they are pretty long, like upwards to a foot long. Other IRS units will have shorter A-arms, which may fit your existing frame better. To use it, you may have to narrow the frame.