LA360 initial timing too high - are there different timing covers?

You know what, A while back someone mentioned the pick-up polarity. I made a mental note of it. Now that popping in the exhaust has come out, it is time to verify that polarity.Ok that was JunkyJimmy post #14.
This is easy-peasy. Just disable the vacuum advance,put the timing lite on #1, and check the idle timing. Then slowly increase the rpm while watching the damper marks. The advance mechanism should advance on a steady march to it's maximum. There should not be any spark drop outs, no retarding at any time, and no jumping around of the mark, other than a couple of degrees that might be chain-slack.So to recap; you want to see a steady march to; timing- all-in.If you see missed sparks,double sparks, or if the timing goes to retard at any time, or starts dancing around, then STOP! Reverse the pick-up polarity. Retard the timing a bit, and start her up. Reset the base timing to 16ish, exact number not important. Then repeat the slow revving to all-in rpm looking for the steady march.And freedom from popping.If/when it works right, you will be able to reset the base-timing to something much more reasonable.

But, if your advance mechanism is working correctly, then you will have to verify the rotor phasing.
And if the rotor phasing is correct, then you will have to verify no water or other contaminants in the fuel. And if that's good, then,clean out your slow-speed circuit. You may have to boil out the metering block in a high-powered carb cleaning agent, to clear out the emulsion tubes, and IdleFeedRestrictions.

But before you go through all that, verify that the manifolds or headers are not sucking air at the head flanges. If air enters the headers there, you will for sure get exhaust popping.