Erratic Timing

ScamperTom said
Thanks, this is just what I was looking for! I am debating getting that plate, but it might just be too easy for me... lol

If you can weld a tack , your are almost always better off not using that plate.

ScamperTom said
I was wondering if 19* was too much. I've read that the total advance shouldn't exceed 50*

That's about right, but clearer to describe it as timing at high speed cruise (60 - 65 mph).
Lets say the engine is turning around 2800 rpm at 60 mph, and you observe the vacuum is around 17"Hg.
Then the mechanical timing at 2800 plus the vacuum advance should equal 50 * BTC.
example:
The '68 318 graphed above shows the distributor with 5* initial. At 2800 rpm it could have a timing at 24*.
At 17" Hg it would have no more than 27* more, probably closer to 26*. 24 + 26 = 50* :)

ScamperTom said
but I guess you really can't dial in the vacuum advance until you get the mechanical right. Just a question: The adjustment in the can only changes the amount of vacuum required for advance, not the actual amount of advance, right?

You got it! It shifts the line on the graph left or right.

ScamperTom said
My engine was built by the PO, but he provided no build sheet, so I have no clue what spec. I should go look at the codes, tho, it will at least tell me what it started as.

LOL. OK. Do you think its a basically stock rebuild?