Question on bored over block

[b17what]

I looked for a bit but not sure how to word the question in search. I bought a rebuilt block to replace my current externally cracked water jacket engine. Just found out its bored .040. I was planning on doing aftermarket rods and pistons because I was planning on 650+ on a built th400. What are my limits on a block bored out to the max?

Should I just dump this block for a untouched one? Would rather not because this ones is really nice besides my issue above.

 

[GC89]

.040 over is the max I have seen. Has it been run since being bored or is it fresh?

If its fresh and they cylinders check round I would say get some .040 over pistons of choice and run it.

 

[b17what]

.40 over is the max I have seen. Has it been run since being bored or is it fresh?

If its fresh and they cylinders check round I would say get some .40 over pistons of choice and run it.

I know it's max. That's why I'm worried. It's got stock stuff in it. I just don't want to blow through head gasket in the thin spaces between cylinders or warping the cylinders if I'm pushing very high boost. Basically I don't want to put $800 Pistons in it if it's just going to not work for what I want and then have to by new ones for a smaller bore...

 

[GC89]

Plenty of people running big power on .040 over, that's not an issue. However if it was bored/built with factory cast pistons that's not the best situation as you normally run tighter clearances with forged pistons.

 

[b17what]

Plenty of people running big power on .40 over, that's not an issue. However if it was bored/built with factory cast pistons that's not the best situation as you normally run tighter clearances with forged pistons.

I appreciate the info!

 

[Jonnymkiii]

It was my understanding that 1mm over (84mm) was the ~max bore size; I know you can easily find 1mm+ over bore forged pistons out there. I am pretty sure you can bore it out 1mm+ and be fine.