Thomas Witt wrote:
>David,
> First let me say that I'm honored to be mentioned in such esteemed company.
>I found the Chevy article you mentioned interesting in that it assumes a
>(too) high cranking pressure (for pump gas) and then stated the long
>duration bleed off reduces the potential to detonate. Put that back into a
>reverse perspective of your high compression, stock cam (reduced bleed off)
>motor and the situation would only get worst.
>
>
Yes, it would. On pump octane. And would need to be compensated for
with a higher octane rating to avoid detonation.
>
>
>165 PSI to 180 PSI Marginal for street motors. Possible hard starting,
>detonation and overheating.
>Over 180 PSI These are all out race engines. A street motor in this range
>will be trouble. Stick to the track. <<<
>
>
Again, I come to a different conclusion. Both of these have more
radical cams as well as higher cranking pressure. The more radical cam
leads to poor drivability in a *street* environment, and the higher
compression doesn't work well with *pump* octane, which is why I believe
they recommend sticking to a track envrionment where higher octane fuel
is utilized and drivability is less important.
The conclusion I come to is that if the car is run on 104 octane daily
and the cam timing is kept stock, the higher compression is compensated
for by the octane increase. There's still going to be an upper limit to
compression with higher octane, but what you've presented seems to
reinforce my original idea that if I were running 104 octane fuel daily
anyway, it would be possible to push the compression to 12:1 to take
advantage of that expanded envelope without detonation and without
sacrificing drivability.
Unfortunately, the only way to test this is to build the thing and see
what happens :-)
Best Regards
David
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