I have looked everywhere and I can't get an exact answer to what I looking to do. I have a 2004 Hummer H2

I have a set of stock LS1 head out of a 2001 Trans Am and I know they will bolt up no problem, but my question is will my stock manifold work or do I need a LS1 manifold? I looked around and it seems the only difference between the two is height.

My second question is, is there any performance benefit to doing this and would my stock computer work with the new heads without tuning?

The only reason why I am thinking about doing this is, I have to remove the head on the driver side due to a broken manifold bolt in the back that I am unable to drill out. So if I am removing the heads I figured why not upgrade since I have the LS1 heads lying around.

Thanks in advance for your advice and input.

 

The "317" castings on some LQ4s are the same heads that come on C5 Z06s. If you look on the driver's side head, just above the coolant temerature sensor, just below the valve cover, you'll see the casting number in the corner of the head. The difference in castings are a larger combustion chamber, IIRC. The valve train is a little different, but that's not the casting... Not only do the 317s have larger intake and exhaust port volumes, I believe the short side radiuses are improved for better flow. I believe the 241s from later LS1s flowed up to about 240 cfm through the intake ports while the 317s (243 heads on the Z06s) flowed around 270 cfm.

Your stock manifold should work on the LS1 heads, but you'd be taking a step backward if you already have the 317s.