mechanical advance question
Thread Starter
Pro
Joined: Oct 2005
Posts: 541
Likes: 1
From: Freeport FL
mechanical advance question
I read the sticky up top there, but am unclear on one item. When I rev my motor up the mechanical advance comes in at about 2500 (actually seems to come in at about 3000 but not drop back out until 2500, but that could just be me). However it all comes in at once. Its like it hits a certain point and the balancer timing marks just roll over from the no advance setting to the mech advance setting. Are my weights sticking? There was a note with my new MSD rotor that said trimming of the weight post bushings might be required to prevent interference, but I dont see how that could be when looking at it.
Advanced
Joined: Dec 2005
Posts: 87
Likes: 0
distributor advance curve
your distributor should start advancing around 1000 engine rpm (500 dist) but you need to do a little research for your specific engine,year,transmission and distributor(number) application.
Last edited by Bob06COUPE; Feb 15, 2009 at 06:05 PM.
Le Mans Master
Joined: Apr 2004
Posts: 7,106
Likes: 38
From: Newark DE
the mechanical advance should start to come in about 200-300 RPM's above idle speed. The factory distributor curves were not very linear but for arguments sake and for simplicity it should be a fairly smooth gradual mechanical advance as the RPMS increase up to between 2500-3000rpm when the mechanical timing is all in.
If you are not getting any mechanical advance until 3000 and than it all comes in at once it your weights are probably sticking and getting hung up on something and them when the RPM's are high enough the centrifugal force becomes enough to force them loose which is the point when you see the timing jump all in.
I'd inspect the distributor carefully to see where the mechanical interference is coming from and fix the issue
If you are not getting any mechanical advance until 3000 and than it all comes in at once it your weights are probably sticking and getting hung up on something and them when the RPM's are high enough the centrifugal force becomes enough to force them loose which is the point when you see the timing jump all in.
I'd inspect the distributor carefully to see where the mechanical interference is coming from and fix the issue
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
It sounds like your mechanical system (flyweights, springs, etc.) are 'hanging up' on something. See if you can locate the cause of the binding. The mechanical advance should be a smooth ramp up to max. and a smooth ramp down again.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The most likely problem is that the weights are not sliding freely on the top plate. It may be corroded or gummed up. Someone may have put too much grease on those parts. Clean them all up and you might be OK. Or...there might be some parts getting pretty well worn. All of the distributor internal parts are available at the aftermarket Corvette parts suppliers.
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