vacuum advance


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By 55Birdman - 17 Years Ago
I have installed a petronix ignition in my 292. Do I need to keep the vacuum advance or can I block it off? Thanks
By sundance241 - 17 Years Ago
I have to ask ,   Why would you want to block it off ?....Sam
By oldcarmark - 17 Years Ago
IF you disable it you wont get any advance on your timing at ALL unless you have changed to a post 56 distributor which has centrifugal as well as vacuum advance!  Pre 57 had ONLY vacuum advance capabilities which is why many people upgrade to the later distributors.  Better performance and bonus better gas mileage.  I guess I should have asked what year 292 you are working on.  I assumed 1955!
By The Bat out of hell - 17 Years Ago
3x2 some times can have a weak vac, but when just going along will be enough most of the time to help MPG out by kicking it up to about a max of 40° full adv., hooked only to base of center carb [#1 carb in P-link], but if not using progresive linkage [all 3 carbs at one time], then it does not have enough vac to use vac advance, in that case you must use the late dist. and set time at full° adv. to 36°.

There maybe some better then this info from some one, but that's my 2 cents.  It's worked nice for me in the past Cool

By Ted - 17 Years Ago
The Pertronix module is simply replacing the points so if you’re still street driving this car, then you’ll want to keep the vacuum advance operational for the extra fuel economy if gives.  As oldcarmark mentions, the year of the distributor is an important factor as the Load-O-Matic distributors (pre ’57) must have the vacuum advance or overall performance suffers.  On the '57 and later distributors, the vacuum advance is most beneficial under part throttle and/or cruise conditions.
By 55Birdman - 17 Years Ago
I didnt know if it was that necessary when you change ignition systems. Have been told its not needed but ....  maybe it is.

thanks