Re: 392 OVERHAUL

[Howard R Pletcher <n9ads@domain.elided>]

On Fri, 5 Mar 1999 13:17:34 -0800 "Dave Pavloff" <pavloff@domain.elided>
writes:
>I have a 392 improoved cooling that I am overhauling and I want to bump
the
>compression rato up to 9.0-9.5 range.How mutch would I have to machine
off
>? would it be better to machine off the heads or the block? I plan on
using
>.030"head gasket. is there anny one out there that has done this?how
mutch
>power gain would I get?
>
>
>
The fact that the piston tops and combustion chambers are not flat
surfaces may throw calculations off a little, but treating them as such
and starting with an 8.28:1 compression ratio and a stroke of 3.65625"
indicates that .045" off the heads would give you a 9.0:1, .072" would
yield 9.5:1, .096" would yield 10:1, and .137" would yield 11:1..  That
should be in the ballpark at least.  

I don't know about better, but it seems more manageable to machine the
heads.  

I don't know just what the limit is, but it seems that I've heard that
the .072 may be approaching the limit of what you can take off without
having to shim the rocker arms to keep the lifters operating in their
proper range.  Check into this if you go this far.

I've machined .050 off the heads of my 345 and this combined with headers
and some porting makes a very nice running engine.  I have no figures for
what the power gain might be.

Howard Pletcher
Howteron Products Scout Parts	

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