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comp. ratio & pinging

To: british-cars@hoosier
Subject: comp. ratio & pinging
From: hiss@fionn.lbl.gov (Eric Hiss)
Date: Fri, 20 Mar 92 15:13:54 PST
I've been reading David Vizard's book on How to Build HorsePower.

I've also just read a few other hot rod books and some auto mechanic text 
books and I just had to point out that some of the postings seem to differ
from what I've read.

first off the bigger the bore the higher the compression ratio can be without
'pinging'

second aluminum heads transfer head better than iron and have less hotspots
and can take a higher compression ratio than iron. 

combustion chamber also has an effect. A hemi head can take the highest comp.
ratio, with wedge following.  

My 429 V8 seems to run just fine on pump gas at 10.5 :: 1  and I've been told
it will take 11 :: 1  with a stock iron head.  It has a 4.1 inch bore or
something around there.

Also noteworthy ... going to higher and higher compression ratio yeilds 
diminishing returns. After about 10 :: 1  the theorhetical gain is only
about 1% per point. 

Also, I read that the majority of octane boosters did not really boost 

I'll try and find that information but as I recall (Vizard?) there was only
one which did anything ....



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