1955 mechanical timing advance

[Al S.]

Timing is set to zero degrees at idle. At 2500 rpms it moves to 40 degrees. The engine runs hot(water temp is 180 at top of radiator and 140 at bottom). and oil pressure drops to 15 pounds at idle (30 pounds at 2500 rpms.
How do we change the curve on the distributor?changed the fly weight springs. will test tomorrow but I'm looking for other possible causes. Any ideas?
Al

[John H.]

Re: 1955 mechanical timing advance

Timing is set to zero degrees at idle. At 2500 rpms it moves to 40 degrees. The engine runs hot(water temp is 180 at top of radiator and 140 at bottom). and oil pressure drops to 15 pounds at idle (30 pounds at 2500 rpms.
How do we change the curve on the distributor?changed the fly weight springs. will test tomorrow but I'm looking for other possible causes. Any ideas?
Al

Al -

Do you have the original 1110855 vacuum advance distributor? Its original max centrifugal advance spec (crank degrees) was 30*-34* @ 3600 rpm (vacuum advance disconnected and plugged), and the vacuum advance unit should add 14* to your base timing setting when connected at idle.

180*F at the radiator inlet is perfectly normal, and 140*F at the outlet says the radiator is doing its job.

[Al S.]

Re: 1955 mechanical timing advance

I do have the 855 dist. and a085 vac. advance. The vac is now plugged. I wanted to confirm the mechanical advance. The spec says 17 degrees max. Glad to see 30-34 in your reply.
I think I had a big vac. leak. I'll let you know if that solves the problem.
Thanks,
Al

[John H.]

Re: 1955 mechanical timing advance

The spec says 17 degrees max. Glad to see 30-34 in your reply.

Al -

That centrifugal advance spec (in the ST-12 Specifications section) has an asterisk (*) next to it, which means distributor degrees - you double that to get crankshaft degrees.