timing with vacuum gauge

[basement]

Oh boy, another timing question for you all. I reviewed abunch of the vacuum/timing posts but never really could find anything that addressed my question so here goes. I know there are about as many opinions on timing techniques as there are sparkplugs in my engine but what about this one. Attach a vacuum gauge to manifold vacuum and adjust the distributer at idle for max vacuum and call that good?

[Chryco Psycho]

never tried it 

[miketyler]

I would say vacuum pressure is a better method to adjust the carb once you have the timing set. I dont think you can be as precise with it. Maybe close though? 

I was just reading an article about that vacuum yesterday. Not so much about using vacuum exclusively but lists problems associated with unusual vacuum scenarios. Check it out:

http://www.centuryperformance.com/vacuum.asp

And a decent article on timing, vacuum advance, etc

http://www.centuryperformance.com/timing.asp

[dodge freak 2]

How I set my timing is with no vacuum advance and rev it up until the mech. advance is all out-like 2000-3500 rpm's depending on how strong those little springs are in the dist. Then turn the dist to give more timing until the motor starts picking up no more speed or running a bit rough  or slows down. Then back it off a bit and lock it down.

Afterwards I looked with a timing light and its like around 38 degrees, give or take a little. Time the motor to what it wants, the most timing while still running smooth

[kudakidd]

at idle turn the dizzy until you get the highest hg reading on the vacuum gauge. Then back it off until the gauge reads 2" less. (10" hg, then set at 8" hg) That will be the ideal setting. It works like a charm

[moper]

I would compare setting timing with a vacuum gage to carving a turkey with a dinner fork.

If it works for you, that's cool. But, it's a very rough and vague way to set things. By ear is just as good. If you want to seriously know how it works, and how and what it does when things are correct, use a timing light. First step is to set the timing curve with a light. Then you tune the carb preferably with a vacuum gage. Then the results are much more paletable... 

[miketyler]

I dont know if this helps but evidently some people time their engines using vacuum as a reference (initially anyway). Here's a response from a Moparts member asking about timing his 383 six pack with MSD. Init timing set at 12BTDC

well, if its a mild performance cam, I'd say you should be in the ballpark @ 12*. Invest a few bucks in a vacuum guage (invaluable tuning tool). Hook the guage up to non-ported vacuum. then adjust the initial advance (at an idle) for the max. vacuum. that's gonna get you pretty well on the money. Once the initial timing is set, you can start to tailor in the advance with the spring kit. The same tuning tool & rule goes for the carb, play with the carb idle mixture screws looking again, for max. vacuum. Once you're there, if you still have a flat spot just off idle, you'll start looking at accelerator pump options & jetting.