Don Malling asked:
> A very knowledgeable person told me that I should not go higher than
> 9.5:1 with standard (cast iron?) pistons.
> [snip]...... and was about to
> go to 9.8:1 and wondered if there was general agreement on not exceeding
> 9.5:1 because of combustion temperature.
IMHO, 9.5:1 is a very conservative figure, and is a good number for people
who are not careful about ignition timing, or live in Colorado, or cruise in
the mountains frequently.
If you are careful about timing, and do not live in the mountains, then I
would advocate that 10:1 is safe.
If you are fanatical about timing, and have a great ignition system (i.e.,
MSD or Jacobs), and are prepared to carry octane booster for your trips into
the mountains, then I would say that 10.5:1 is at the edge. If you have a
high-tech multi-port fuel-injection and engine management system, I would
guess that even 11:1 would be safe with stock TR6 pistons.
I ran 10:1 on my Pantera, and ran it regularly (and hard) at 5,000', with no
detonation. Other Mates were running 10:1 and 10.5:1 with absolutely no
pinging.
That9s my belief, and I'm putting money and my motor on 10.5:1.
[Don9t ask me for stock market picks] YMMV.
Shane Ingate in Maryland
|