Manifold Vacuum Advance what am I not getting?

340inabbody said

I don’t know what you mean by “run good”. That’s a hard question to quantify. When I tuned it, I didn’t look at my timing light at all. I timed it based on what sounded good and smooth and what gave me the highest vacuum. Will it run at 24° yes. Does it seem to run better at 42° I believe so. I believe an engine is more efficient when you have higher vacuum. So I think I answered this question correctly or is best I could.
I can also say that I repeated this tune 3 times and all three times it came out to 42° so it was consistent.

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Jacking timing to an engine with cranking compression that high is a power killer.

Manifold vacuum is a bad way to select your initial timing?

Why, because long duration, high overlap cams cause EGR. This does require more timing BUT you can never get the idle efficient enough no matter how much more than optimal initial timing requires.

Set the vacuum gauge aside, set the initial at 24 and start there without MV hooked up.

I just went through this last Sunday. I had to unfuck something I did correctly because some jack *** read that you need as much initial as the engine will take.

It was garbage. Did it idle “smoother” with 30 initial? Yes, but the time was off. It was smoother but it ran like ****.

I put it back to where it was supposed to be and even the owner was smart enough to see it was screwed up.

What spark plug do you have?