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cosmo
03-07-2005, 11:36 AM
ok i've installed a double barrel carb,a petronix ignition, i have stock cam, and a stock exhaust. by the way it's a 63 lark 170 ohv 6 cyl. my quetion is what should my advance settings be? what should my idle advance be, and what should my mechanical advance be then for wide open throttle what should the advance be?

Sonny
03-07-2005, 04:49 PM
The bad news is we don't have too many options for adjusting the vacuum advance, and the best way to adjust mechanical advance is to change/adjust the little springs that control the counter-weights inside the distributor. The brand-x boys have all kinds of help in these areas so you can check out what's available to the chevy crowd if you have the Delco distributor, otherwise it's gonna be a hit and miss deal adjusting those springs yourself. If you don't find a replacement mechanical advance spring kit for your particular distributor you have to get BOTH of the springs set almost perfectly alike, something that's pretty tough to do by eye.

Get yourself a good timing light and something to read engine rpm. With the advance system connected normally, slowly rev the engine and watch the timing mark on the crankshaft pulley, you should see the timing start to advance almost immediately, note the rpm when it first starts to advance. Disconnect the vacuum line at the vacuum advance and plug it. Slowly rev the engine again and note the rpm where the timing starts to advance, this will give you a true picture of when the vacuum and mechanical advance is coming in. You do not want ANY advance at idle. You want the mechanical advance so that you get full advance no later than 3000 rpm.

You can adjust the vacuum advance, but you have to have the type of advance that has the removable end, then you can change the spring and/or metering orifice to adjust vacuum timing, something that takes a LOT of time and testing.

Get your full mechanical advance set to come in at no later than 3000 rpm, set the initial timing 2 degrees advanced from the book setting to start with, (with the vacuum advance line disconnected), re-connect the vacuum advance line, drive it and check for pre-ignition detonation, (rattle), under load. If it's good there, then advance the initial timing by two more degrees and keep doing the same thing again until you find the rattle. When you find the rattle, decrease it by two degrees and leave it there. I think you should find that you'll get at least 4, and mebbe even 6 degrees advanced timing out of it.

Bottom line, unless you can find an adjustable vacuum advance to fit your distributor, adjust the total mechanical advance to hit no later than 3000 rpm, leave the stock vacuum advance system in place, find the timing "rattle" under load, drive it.


Sonny
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