Timing- how much advance at speed (45-50 mph)

gearloose

gearloose

Member
Right now I am running 5 degrees advance at idle and it purrs as much as an A can. What would be a good advance at speed w/a Brumfield head and what could the rpm be?
 
my sedan has a BF head and it idles well at just a few degrees advance, too. For the most part, I drive it at half mast, or 20 degrees. Only at 45-60 mph on a flat road do I advance it more. Rich Falluca of Antique Engine Rebuilding suggests not to exceed 28 degrees at highway speeds with a high comp head. That is about 4 clicks up from the bottom of the register. Larry Brumfield suggested staying shy of pinging by a click or two, but I can't hear the subtle pings anymore, just the loud ones. By the time you hear the loud pings you are much too far advanced. When pulling a hard hill I back off a click or two ( 3 to 6 degrees). After a while you will learn to feel the engine. If it gains power with more advance, that's fine. Just at the point where it fails to gain power with any more advance, you are in the right zone. Further advance will rob power. You can find Larry on Ahooga.com and get his opinion.
 
Are you setting the timing at exactly TDC with the spark lever fully up?

And then going advanced from there?
 
Listen to the engine! At a given speed lower the spark lever slowly you will hear the engine pick up speed. When the engine stops picking up speed stop lowereing the lever. Due to adjustments, slop, gaps, compression, etc the actual lever position will vary from car to car.
 
cars56 said:
3/4 up the quad to all the way
The car will let you know
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I agree. If the engine starts pinging you're too far advanced. It's like "How many pounds should I torque the wheel lugs nuts?" I just make sure they are tight that's all. You just can't put a number on how much advance to use.
 
i run 35* total with 5* retard at start . i run mine full advance all the time & it does great . no ping or detonation . no problems at all . if i retard it a lil , i lose power & the motor sounds labored . 6-1 head .................. steve
 
steve norcal said:
i run 35* total with 5* retard at start . i run mine full advance all the time & it does great . no ping or detonation . no problems at all . if i retard it a lil , i lose power & the motor sounds labored . 6-1 head .................. steve
Click to expand...

steve,
Wow; not saying I don't believe you but that is really surprising. I suppose you're doing hills and using regular gas too?

Otherwise, my understanding is that maximum advance is actually needed at intermediate loads, which is why newer cars use a vacuum advance system to supplement the centrifugal system. At high loads, which you may qualify for as you push to 50 mph in a Model A, the vacuum advance backs off and returns you to the centrifugal "baseline" advance.

steve
 
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