[mfuller]

Everyone:

Looking for a bit of help here, now that I'm hip-deep in my engine build.

A bit of background......picked up a 47K mile 3400 long block and my builder has it almost completely torn down. Insides were a bit nasty with oil/sludge, but the crank tuned fairly easily.

I am building it up with a 1280 cam, and a totally awesome set of street/strip heads that Ben did for me. Flowmatched, cc match, stainless valves...the full monty. Plus a ported LIM to match. Already have 65mm TB, ported plenum, headers, etc.

Now, since I have the thing apart, do I just go for broke with a 1.00mm (.040") overbore? CR calculator says my compression ratio goes up by about 2 tenths of a point, from 9.88:1 to 10.09:1.
Or do I just wait for the machine shop to let me know the condition of the cylinder bores? I'm betting on new rings at the very least, but if the piston skirts are scratched up, likely the cylinder walls are too and it'll have to be machined anyway.
Oh, and I'm going to have the machine shop balance the rotating assembly, which obviously can't happen until we get pistons.

New 1.00mm overbore Sealed Power pistons and rings are about $350 from Rock Auto.

Thanks in advance for your opinions/advice.

[bszopi]

I'd bore it if I were you. The slight increase in CR will help out power wise, as well as bumping the overall displacement closer to an actual 3400cc. If you are going to buy pistons anyway, then might as well just go with the slight overbore. Now, if you were planning on using the stock pistons if all looked ok after disassembly, then it might lean me to say just save the $$.

[project89]

save some cash
http://cgi.ebay.com/ebaymotors/GM-3-...QQcmdZViewItem

[blackbombshell95]

I had my 3400 sonic checked when it was getting rebuilt. Here is a picture of the sonic check.

http://60degreev6.com/forum/gallery/...=3&userid=6428

The machinist recommended .030 over just to be safe. So thats what I did on my 3400.

[gectek]

keith black makes them over 1.00mm iirc...and i dont think they would make them if they turned the engine to crap. i went .030 but prob would rather have gone .040 in hindsight...oh well for another build i guess