Armydad

Hi all,

Does any one know what the approximate hp and torque gains are with a .020 overbore. Also does the increased surface area of the piston head effect comp ratio or is that just a function of the combustion chm.


Thanks

2000GT4.6

A .20 will add virtually nothing to your 2v car, espcially with stock heads/cams/intake. Even most of the stroker kits do not add alot of power on built cars.

Armydad

Well actually I will be having ported SVO heads a Crower blower cam and probably the FRPP s/c. Also headers full exhaust, CAI, TB, I probably should have mentioned all that, sorry.

JD1969

You don't bore an engine for added HP. Boring is done to true the cylinder walls and provide a good seal for the rings.

hotrod7687

+1

You might get a 1-2 hp gain if your lucky. You buy the pistons with the compression ratio you want, they will already have the overbore factored in.

Sxynerd

How Does this motor differ from any other? A bigger bore means more power! It Might not be huge number but it does give some. My Experience is with my 71 notch w/ a 302 that was bored and stroked to 357! 500Hp w/ dual quad carb's a beast, to say the least... And about a dozen hand built Chevy 350's.... A few were strokers.. Why doesn't it add power in a modular?

Mike

droptoppony

[sm=exactly.gif]

.020 overbore is just a clean up...only adds like 2 cubic inches.

Armydad

thanks for the response, I agree that perhaps.020 is more of a trueing of the cylider walls, but why then would someone need to go bigger? To increase displacement and make more power. if you need to overbore .040-.060 just to true the walls, you should look for a new block.

Stang9946

Why do you think guys take 350s and stroke them to 383s? More power! More potential! You don't bore out a 350 30 over and put a 400 block crank and pistons in it to seal rings. Don't know where you got your information from.

droptoppony

some will do a .020 over on an engine rebuild then if they make a change take it out to .030 over...modular blocks shouldn't be taken out much more then that thus the reason for resleeving them when going with a big bore. Now a big bore will add some power.