I seriously doubt that you'd be able to run 87 octane on a TR6 with 9.0
compression. Heck, I didn't even run such a low octane with the stock
8.5:1 compression. Better to spend a few extra bucks on the good stuff
(92+ octane) and have some piece of mind. Detonation will take care of
those cast aluminum pistons pretty quickly. An expensive mistake. If
you want to go to 9:1, run high octane gas. If you want to stay at 87,
I wouldn't think anything over 8.5 is safe, and even that may be risky.
As always, when doing a compression upgrade, it's better to take a
little off the head than a lot. You can always take more off the head
later and bump the compression up a bit more, but you can't put any
back on!
Tim Holbrook
1971 TR6
--- Kendall Larsen <klarsen@inreach.com> wrote:
> Tim/Dick you guys really seem to know this stuff so I thought I'd
> double
> check what the machine shop told me. The guy there said that 9.0:1
> would be
> able burn 87 with out retarding the ignition. what do you guys (or
> any one
> else!) think? I'm thinking I'm going to shoot for 8.75 because the
> cylinders
> haven't been bored out at all yet so when that becomes necessary I
> don't
> want that extra volume to bump my compression ratio into the
> unworkable
> range.(when I serviced the engine I determined a honing would be
> sufficient
> for now and, yes, the rings did seat nicely. ) I'll check those
> numbers all
> over with the machine shop guy again before he starts milling the
> head but
> I'd like to be armed with second opinions before I speak to him
> again. I
> would prefer to be able to burn 87 but still get a performance gain
> from an
> increased compression thus all my fussing about where to draw the
> line.
> Thanks guys.
>
> Kendall Larsen
> 74
>
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