LT1-LT4 Modifications - with stock pistons and 58cc chamber what is the CR

we are building a friend of mines car and he is running a stock bottom end with 58cc chambers i know that the lt1s stock are 54cc so he will have a little less compression can anyone give me a figure we are just curious and i told him id ask on the forum

Actually if you go to a thinner gasket you could still net a tiny compression gain.
The stock aluminum head LT1 gasket is THICK at .049, there are popular inexpensive reliable gaskets as thin as .026 and .029.