In an article in this month’s Hot Rod Magazine (January 2019), a question from a reader is why their engine (Chevy
330 355 as I recall) is performing poorly after they installed new aluminum heads and a new Holley carburetor. No changes to the camshaft or block. In order to get the engine to idle & run well they now have to advance the timing to 30 degrees BTDC base timing. Hot Rod suggests this indicates a problem b/c the normal base timing for this engine is usually around 16 degrees BTDC. It’s the same distributor, but it had to be temporarily removed in the process of installing the new heads of course. Hot Rod says the problem may be the distributor installation is “off”. I can’t figure out how that could occur. It seems like all that’s required is for the rotor to be pointing more or less at the number one spark plug terminal at TDC compression stroke. Beyond that, it’s just adjust the timing according to the timing light as viewed on the balancer, right?
My question is: How could the distributor re-install being “off” result in the need to idle the engine at 30 degrees BTDC?