Re: dyno/ignition timing 1600

[bearbvd@domain.elided (Greg Hermann)]

>could the timing at 26 btdc be because of mixture being wrong?was the timing
>light reliable? I have never had an alfa run good with less than about
>35(because of high compression/pinging)-stock engines seem to like 38 to
>40-any other experiences?

It all depends on the shape of the piston crown/combustion chamber
geometry. With stock pistons, more than 40 degrees total advance (as much
as 46 if you have cold air to the carbs) is not an uncommon requirement,
particularly with stock compression ratio. With pistons with a good, tight
squish area around the fringes of the chamber and a flat topped dome, 31 to
33 degrees total is more like it, and there is much less octane
requirement, even with compression  ratios approaching 12 to 1.

A lean mixture and/or hot air to the intake will definitely limit how much
advance an engine will accept.

The most interesting aspect of running the squish type chamber shape is
that the engine will run without pinging with its advance in the
mid-forties, but it will make a BUNCH more power with the advance set in
the low thirties.

Regards, Greg

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