I like .250-.300" for any engine. All but 1 of the lq4 blocks I have tested were less than .175 in between cyls, and most are between .120-.150". Thrust is usually double.

 

Was that with a stock bore?
Right now my block is 4.030 and it had some cylinders with some ring grooves and debating on going on up to 4.065 for off the shelf ls3 pistons. I've read people going up to 4.080 and 4.125 with filling the bottom of the block.

 

Why don't you tell us what your working on before asking for help.

Each Block is different and so is every casting. You would have to sonic check a block in various parts of every cylinder to know what your starting with. I believe the rule of thumb is to maintain at least .200 minimum wall thickness on an NA Block. Forced induction, Nitrous, High compression with different fuels would obviously require more wall thickness for the added cylinder pressure's. Also things like filling the block will effect the wall strength as well. Every machinist will have something different to say on the subject.

 

All Im looking for is a rule of thumb what thickness is necessary when I take this block and have it sonic tested.

 

I see you posted more info as I was Typing in my response earlier.

I hope Stock48 and I were able to get you a range to look at. I think what he has said would fit good with the higher cylinder pressures.

I haven't seen one of those blocks Sonic checked but I think you might be able to go .060 and still be ok.

Keep us posted on what the Sonic check revels for you. I would be curious to know.

 

Yeah, I pretty much believe anything over .030 on the LQ blocks should be sonic tested.