You look to have the same MSD billet distributor I have. I have a source for custom bushings. The largest bushing MSD makes is 18. Not enough for your motor. I think they come in 23/28 or so. With no vacuum advance, it's even more important to have more timing at lower rpm. The whole point of vacuum advance is to start ignition sooner under high vacuum conditions. Fuel takes longer to burn in that scenario. While your engine never has high vacuum in comparison to a stock engine, it does in comparison to idle and load conditions. I wish I had vacuum advance on mine. It would need to be adjustable due to our naturally low vacuum. The other factor is a clean idle. The more inital you have, the more vacuum you create. That is important for a consistent idle that doesn't foul plugs. That keeps you out of the transition circuit in the carburetor. I've thought of locking mine out but my combo works fine as is.
I'm not trying to step on Rich's toes, but our builds are on the same piece of paper and I've spent countless hours fiddling with alot of this crap.
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Todd
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