Robsproject

Ok i know this is probably not the best place to talk about GM cars. but I am planning a project Fbody. (ls1 trans am) I want to set it up for open road race. Big power but I want better high speed handling and for this I want IRS.

My question is, What kind of power is the 03+ cobra IRS rear ends able to hold, and what kind of supporting mods would I need for ~800 HP

MTShambles

800RWHP = Bad for IRS.

Why?

Halfshafts. When you get that high in RWHP, any amount of wheel hop can shatter a halfshaft easily, and they are not cheap to replace. Not to say that IRS cant be stiffened up in order to hold that amount of RWHP, but ive seen halfshafts shatter from just having 400-550HP in a 03/04 Cobra IRS setups.

Most of the IRS things from Maximum Motorsports (http://www.maximummotorsports.com) should stiffen you up a bit, but if you are going that high in RWHP, I would shoot for a solid rear rather than a IRS setup.

JD1969

Besides what MT just said, you don't need to have IRS to make an F-body handle extrea,ly well. Go to LS1tech.com and ask around in the suspension section, there are a couple of members there who really know thier stuff when it comes to road race suspension on an f-body.

Tim37

or buy a vett

Robsproject

I have been posting on ls1tech for a while, and I know that Fbody's can be made to handle very well (i just sold one Trans Am project car) but I am looking to hit the 200 mph club with open road race in nevada with this one. Its going to end up with 2.73 gears and that should reduce the stress on the rear, Its going to be a twin turbo setup with lots of aero mods, but I know from my current car that the IRS is very good for high speed handling dynamics.

But what I am hearing is that Half shafts are the problem? is that the main potential source of failure? its not going to be launched hard as in a drag race.

Tim37

the rear will hold a lot fo power but you can't be hard on it.

Bullitthead

I believe an IRS like the one in the '03 & '04 Cobras can handle quite a bit of horsepower as long as you are not trying to do a hard launch with slicks or drag radials. This is what torques the halfshafts and makes them shatter. If you are going to be using the car to make a high speed run, I think an IRS will be fine. I've seen companies selling strengthened half shafts for the Cobras that could handle quite a bit of extra horsepower. I saw the ads in MM&FF months ago, but unfortunately I can't remember the company's name...

Anyway, I think going with an IRS is fine for your needs. And besides, who wants to be just like everyone else anyway?

Robsproject

Yea there will be minimal hard launches, the car will be built to have "long legs" geared for the highway and tuned for power lower in the RPM band. My second challange will be underhood heat, For this I will probalby need to do a custom twin turbo setup that will locate the turbo's a little farther down, about where mid length headers drop out. It seems to be a project that will be longer in planning than building just so I can get everything in place before moving on.

MTShambles

Even with that amount of power, I have seen level 5 halfshafts shatter under that much torque/power.

If you are going to do it, be very careful.