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Old 02-11-2013, 05:59 AM
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Originally Posted by cruizin uncle bob View Post
Thought maybe someone out there would have idea about a problem a friend of mine is having with his 41 Chevy. We built this car about 2 years ago, it had 350/350 eng/trans, he burned the engine up then changed it out with a 283. It was running a HEI distributor which went bad and we installed old OEM points distributor with Pertronix upgrade. Are running resistor type coil as suggested. The engine starts great, idles really good, but when you put in gear and try to accelerate it pops and falls on it's face, if you feather the throttle it will go but as soon as you get into it, it pops and goes dead. I suggested to him that vacuum advance could be the problem what do you all think. Plan on checking all the grounds to the chassis and engine. Engine timing has been checked and re-checked. Carb is new and I don't really think it is a fuel problem. Any suggestion is appreciated.
Check it to see that the vacuum advance is working like you said to begin with.

BTW, do all the initial and mechanical advance tuning w/the vacuum advance disconnected and the line to the carb plugged. Once you're done tuning, hook the vacuum advance to manifold vacuum (aka full time vacuum).

Verify the timing marks are showing TDC.

Most vacuum advance cans give too much advance; you really only want about 12-14 degrees w/a mild cam and "normal" compression ratio. To limit the total amount of vacuum advance you will need to physically limit the vacuum advance can's travel w/a vacuum advance limiter plate like the Crane p/n 99619-1. This part also fits the points-type distributor. Or you can make one.

Then use a timing light to see that the mechanical advance is working as it should. If you don't have a dial back light, you can make a timing tape to see what the total timing is.

I would give it more timing if you're at or below 6-8 degrees BTDC (like has been mentioned already). You use more timing for a bigger than stock cam.

Be sure the total (mech. plus initial timing, no vacuum advance included) isn't higher than about 36 degrees BTDC (stock heads), and that the mechanical advance is all in by 3000 rpm or less.

More info on setting up a performance timing curve is here. Balance the initial plus mechanical advance figures as needed. As an example, if you use 10 degrees initial, you'd use 26 degrees mechanical (36 total is the target, minus 10 degrees coming from initial = 26 degrees mechanical). 15 initial gets 21 mechanical, et cetera.
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