I don't know much about ZL1s, but I have always liked to retorque head bolts and exhaust manifold bolts after running the engine for a while.
I have read somewhere that the bolts are all longer on the aluminum engines, and that why you can apply the same torque as on a iron engine without stripping the threads.
But I'm not the expert. Fortunately, I happen to have recieved something nice in the mail today. So here is what the Motion Performance Chevy Performance guide had to say on this subject back in 1971.
