Chris,
My first engine in My 67.5 Solex was assembled by Bob Sharp Racing, and was
about 12.5:1. The compression was raised by using the domed top 1600 pistons
that were fly cut for valve clearance. The head was also milled a small
amount .00020 I think. I had three problems: 1. It would only run without
detonation if I used Sunoco 260 which was around 104 octane, which would be
about 96 -97 with today's R+M/2 ratings. In fact the Sharp team used 100/145
octane aviation gas. 2. With the combination of this compression and very
advanced timing, the starter couldn't cope. I had to install a separate
starter button, I would get the engine cranking without the ignition and
once it was turning I'd switch the ignition on (which I had wired through
the heater fan toggle switch) and it would catch right away. 3 and most
important, the engine did not last too long.
The next Sharp rebuild had 11.7:1 compression, and 30 plus years later it's
still in good shape(of course it been in storage for 25 years).
Jerry Krakauer
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