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Re: Cylinder head questions

To: Scott Gardner <gardner@lwcomm.com>
Subject: Re: Cylinder head questions
From: Aron Travis <atravis@spacey.net>
Date: Fri, 13 Jun 1997 16:52:42 -0700
Scott Gardner wrote:
>   What's a good
> compression ratio to take full advantage of 93 octane gas?

I think that the upper limit is 10.5:1, 11:1 if you polish the chambers.
Shoot for 9.5:1 to 10:1. The book "Auto Math Handbook" by John Lawlor
is good with the equations for figureing out stuff like this.
I'm running approx 10.7:1 on my Galaxie, I can tell the difference
between 93 and 92 octane gas. I run 12* BTDC, but will ocasionally
have to back off to 10* or so if it's being truculent. I think high
compression is worth it for the performance and added gas mileage, but
your engine will be more sensitive to timing and carbon. Therefore
you have to keep track of the tune more.

> Lastly, if I do it and it turns out that I took off too much and the
> engine pings on 93 gas, what can I do? 

Octane booster, timing, water injection, runing the carbs richer will
sometimes work. I don't think you'll have a problem. 

> Double-gasket the cylinder head?

This would be asking for more trouble. MOWOG likes leaks, double gaskets
can leak more. With some performance engines you can have the choice of
thick or thin gaskets, but I don't know if the MGB has that option.
Check with companies that cater to racers.

-Aron Travis-
"always in a automotive frenzy"

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