s346k

iTrader: (4)

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?

Mangled03gmc

iTrader: (95)

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

s346k

iTrader: (4)

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.

budhayes3

iTrader: (19)

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.

Mangled03gmc

iTrader: (95)

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

s346k

iTrader: (4)

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.