Mr. Sir

Does anyone have any power comparisons between similar combos where the only difference is the bore? I'm mainly interested in 4.030 vs 4.065.

Mr. Sir

Bump.

A.R. Shale Targa

iTrader: (2)

The combustion chamber shape and the bore diameter are extensions of the
port in a sense with the valve in the way. Obviously the larger the valve the
more important the chamber and bore become. The only true way to test for
what you're asking is to reduce the stroke in order to maintain identical cubic
inches since 6-7 cubes can easily increase 8-10 horsepower alone. Just know
that an increase in bore diameter WILL help low and midlift flow when a 2.165"
valve is used.

Mr. Sir

I don't mind that it's an unfair comparison; I'll probably be getting an iron block when (or if) my current engine goes, and was just wondering if spending a little extra on a block capable of 4.065 bore would be worth it. 8-10hp isn't worth it. 25-30 is.

Tainted

iTrader: (9)

It wouldnt be much to bore your current motor out and stroke it while youre at it

The less shrouding and more cubic inches the better

bww3588

iTrader: (49)

Only true way to get an accurate comparison would be to use a flow bench using different test bores. Obviously, the larger bore will flow more even if the valves were not shrouded, but it should give you an accurate comparison given the correction factors that can be applied to the numbers on the flow bench.

Mr. Sir

Of all the people here, who would be the most likely to have this information?

dodson55

iTrader: (18)

i wouldnt see that much of a power difference at most 5-10 difference between the 4-4.065 and even less between the 4.03 and 4.065 gm did use the ls3 style heads on a 4 in bore engine in the l76 g8 engine