[olddog]

I was reading through a book and found this information. I remembered you asking the question. It is not clear if this was factory setup or what Ford recomended for performance applications. This is for the 351C 4V. It referred to a dual vacuum diaphragm canister distributor and said for auto tran hook up only the outer diaphragm canistor to manifold vacuum not ported vacuum.

Set initial to 16 with vacuum disconnected.

Centrifugal Advance Curve:

Dist rpm dist deg
400------ 0
500------0.5
750------3.5
1000------6
1200-----8.5
1300-----9.5
1400-----10

Eng rpm Eng Deg
800------0
1000-----1
1500-----7
2000----12
2400----17
2600----19
2800----20

The mechanical giving 20 plus the intial of 16 gives a total of 36 deg at 2800 with no vacuum.

Sorry for the late reply, but I just read it.