im building a 383 with stock 243 heads. i want it to be pump gas friendly so what would the max compression ratio need to be? im going with a big cam like a ms4 or the eps 238/248 cam. what size piston should i go with? i want to stick with wiesco or diamond since i am going to be spraying it. thanks in advance.

 

From what I read and hear an ls1 block can only be bored out to .100 safely. and compression no higher than 11.5

 

Do NOT have your block bored out .100, that will ruin a perfectly good block. Most 383 kits end up in the 11.3-11.7 compression ratio and run a 3.905 bore.