Mechanical advance in old school C5AF-E distributor

[dcdoug]

I thought I might pose this question in a separate thread to my thread about rebuilding a 1960s Ford distributor (as not all of you may be interested in where to find lower distributor shaft bushings....).

For reference: This is for a 1966 OEM C5AF-E distributor with mechanical advance in a 427FE with the "B" cam (.500 lift, .242 duration). Bore and stroke are both standard. Distributor was dual point and I converted it to pertronix ignitor ignition.

I have a question on the mechanical advance cam adjustment. My cam has two options, 15L (15 degrees distributor advance, 30 degrees at the crank) and 10L for (10 degrees distributor advance, 20 degrees at the crank).

When I removed the distributor, 15L was on the limit pin, but I don't know that it was ever advancing properly and knowing that FEs like 16-22 degrees of base timing (mine was set at 22, but I'm not sure I had much/any advance, assuming of course my dampner isn't slipping - I'll check that), it seems that adding another 30 degrees on top of that for a total of 52 would be WAY too much. Even with 16 degrees base timing, 46 total timing seems like it would be way too much.

Seems like I should rotate it to the 10L/20 degrees advance setting?

Thoughts?

And if I do this, as long as I rotate the assembly so that the rotor is in the exact same position as it was when I took out the distributor, the timing should be close to what I started with, correct?

For now, please don't post that I should upgrade to a decent distributor (new), etc. If this proves a big PITA to get dialed in correctly, I will come back and ask for the best FE distributor and I'm sure we will have another lively discussion. For now, I'd like to keep my engine as period correct as possible.