What would be gained by just going with a overbore rebuild? Lets say that the engine is stock for all intents and purposes. Say you need a rebuild at like 125K on a bone stock LT1, obviously 350ci. Say you have a machine shop build you a balanced and blueprinted fully forged 361ci (.040 bore) LT1 with everything stock just like the factory LT1. Would you see any hp/tq differences with everything being the same? Thanks guys.

 

Nothing worth mentioning. Coupla hp at best. Forged stuff does not produce more hp, so the only gain is from the (marginal) displacement increase. The bigger bore will also increase CR, all else being equal, so there would be some gain there. Going 0.040" over leaves nothing for a future rebuild, BTW. HP gains wil come from work on the induiction system (heads, cam, intake) primarily and also the exhaust system.

Rich Krause

 

Yeah, I didn't think it would be much. I was just wondering about going ahead and doing a rebuild now and put together one hell of a stout starting point. Then maybe a month down the road put a real nice heads/cam package along with exhaust. Then obviously with the forged internals spray the heads/cam 355/361 to the moon.
Just a off the wall question, does the CR matter in a sprayed engine. I know without a doubt turbo/blower motors you want less CR for best results. How about a spray motor? Can you get away with say a low 10.X:1 fully forged 355/361 or would you want a little lower CR? Thanks

 

And just to keep the math correct:

3.48 x 4.030 = 355.12
3.48 x 4.040 = 356.88
3.48 x 4.060 = 360.42 (as Rich mentioned.... don't go there)

Nitrous is no problem with high compressions.... I run 10.8:1 with a 300-shot and that's considered "lame" by some people, who prefer 12.5:1

 

okay so probably best to do a 355 for future rebuild, and if I only plan on spraying, still shoot for high compression. So a 12.0:1 355 spraying a 200 shot on a fully forged bottom end is no problem what-so-ever. Sounds good.

 

What Fred said about N2O and compression!

Rich Krause