anyone bored their lm7 to a 3.9 bore, used ls1 pistons/rods, and threw your stock 5.3 heads back on it? any idea what kind of ptv clearance you have? any valve free drop measurements?

 

There have been a few that have had it bored that much, but it makes the cylinder walls extremely thin,esp towards the bottom of the stroke. IMO if you are wanting to make a 5.7, just find a used one and put in its place... (what you got in thure good to eat) Love the avatar

 

thanks on the avatar. i am asking because i was given a bad lm7 (complete minus acc) and stock ls1 internals. i am going to do it, but i just wanted to ask a few questions before getting started. i plan on leaving the heads alone (706) with exception to adding ls1 valves and having some minor work done to support the bigger valves. i just think that having those bigger valves and a (61cc?) head might cause problems with a flat-top piston. the largest cam i'd use is an ls6, and that's only if i find a good deal on one.

 

Be sure to have the block sonic tested before you overbore it, because as John mentioned, the cylinder walls get very thin and could be problematic in the future.

 

Why not get a set of 241 or 853 castings, then run the cam you want??

 

because i don't want a big cam. and the ls1 castings will eat at my compression. when i am ready for a big cam, i will have a vic jr, accufab tb, and flycutting to do.

i want to go fast on stock parts. stock ls1 intake, manifolds, etc. shouldn't be hard to do in a 2800lb car.

edit: any recorded instances of thin cylinder walls being a problem? i've seen a lot of 360cid sbc motors that "should've" came apart or overheated or whatever, but never did. i had one of them haha.