Ignition Timing Advance
Junior User
Joined: Dec 2000
Posts: 80
Likes: 0
From: Lakewood, CO
Ignition Timing Advance
How much is too much for total advance (Mechanical and Vacuum) @ 3000 RPM or so?
My 78 F-250 4X4 with a 351M advances to about 50 deg btdc for total advance. It doesn't ping, and runs really well. Of course, I am always trying to optimize gas mileage. Initial timing is at about 11 deg btdc. The distributor is new. Why so much advance?
Thanks,
Jeff
My 78 F-250 4X4 with a 351M advances to about 50 deg btdc for total advance. It doesn't ping, and runs really well. Of course, I am always trying to optimize gas mileage. Initial timing is at about 11 deg btdc. The distributor is new. Why so much advance?
Thanks,
Jeff
Elder User
Joined: Oct 1999
Posts: 917
Likes: 3
From: Kelseyville USA
Ignition Timing Advance
Jeff, I think that 50+ is way too much..
I kinda got a rude awakening when checking out the mechanical advance on rebuilt distributors.
Here is what I have found..... Under the points plate is the mechanical system, springs weights etc.., on the mounting/rotating shaft the side arms are stamped 13, 15, 10, etc. That is the TOTAL mechanical advance that the dist can be set up for ONLY one side matters... NOW, take the number and DOUBLE IT.. Thats what the mechanical advance will produce...
SO if you use the initial timing say 12 geg. then add in the mechanical MAX..say 26 (13x2) thats 38... Now add in the Vacuum produced advance and you can well go over 50deg.
I had to look through the rebuilts on the shelf to find one set up for 10 deg.MECHANICAL! then I installed a crane adjustable advance (like 12.00). Now I can control the vacuum advance MAX.
I like to keep the TOTAL below 38 deg at 3,000....
I think this link is still good >>http://www.fordmuscle.com/archives/2000/03/timing/index.shtm <<
Kinda goes deeper on what I said.
__JOHN__Õ¿ö
FTE Club #7
Member-
http://www.cruisin-north.com/
Santa Rosa, Calif.
72 F-250
ICQ#6030753
http://www.ford-trucks.net/users/jbhf250/
https://www.ford-trucks.com/pictorial/big/1972_f250_2.html
I kinda got a rude awakening when checking out the mechanical advance on rebuilt distributors.
Here is what I have found..... Under the points plate is the mechanical system, springs weights etc.., on the mounting/rotating shaft the side arms are stamped 13, 15, 10, etc. That is the TOTAL mechanical advance that the dist can be set up for ONLY one side matters... NOW, take the number and DOUBLE IT.. Thats what the mechanical advance will produce...
SO if you use the initial timing say 12 geg. then add in the mechanical MAX..say 26 (13x2) thats 38... Now add in the Vacuum produced advance and you can well go over 50deg.
I had to look through the rebuilts on the shelf to find one set up for 10 deg.MECHANICAL! then I installed a crane adjustable advance (like 12.00). Now I can control the vacuum advance MAX.
I like to keep the TOTAL below 38 deg at 3,000....
I think this link is still good >>http://www.fordmuscle.com/archives/2000/03/timing/index.shtm <<
Kinda goes deeper on what I said.
__JOHN__Õ¿ö
FTE Club #7
Member-
http://www.cruisin-north.com/
Santa Rosa, Calif.
72 F-250
ICQ#6030753
http://www.ford-trucks.net/users/jbhf250/
https://www.ford-trucks.com/pictorial/big/1972_f250_2.html
