Timing engine by vacum?

[010175]

1961 GM engine and i read that you cant time engine by a timing light because of new gas. True or Not? They said to use a vacum gage but how? Thanks Dave

[maxwedge]

Not true, set the timing to spec and drive it, under heavy load you may get a slight ping, normal. Worn timing chains and loss of compression on an older engine actually may allow slightly more base timing.

[010175]

Thanks I will put a light on it.. Dave

[MagicRat]

Vacuum gauges are handy for setting carb idle mixture and for detecting faulty valve timing, but vacuum is not directly affected by ignition timing.

[consultIII]

i agree that nothings more accurate that a timing light.
but to play devil's advocate....

my old motive power instructor (who was a ford master tech) told me he used to time certain older vans by vacuum as you couldn't get a light on the marks.
the procedure (if I remember correctly...which i may not) was to turn the distributor to achieve max vacuum and turn back so it drops 2" vacuum from max....or may have been max vacuum and turn back until get 50rpm drop?

comments

[j cAT]

Originally Posted by 010175

1961 GM engine and i read that you cant time engine by a timing light because of new gas. True or Not? They said to use a vacum gage but how? Thanks Dave

review this thread I posted in april of 2008. this chart is what you need to set up the timing for optimal performance...

the use of relead is needed when running these older engines..this should protect the valves from wear..


http://www.automotiveforums.com/vbul...d.php?t=897935