Distributor advance curve
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The curves are approximately linear from (the RPM) where the mechanical advance starts to kick in and until it maxes out at the positive stop. All distributor curves can be modified by altering/swapping weights, retention springs, and stop collars.
Binding and/or mechanical restrictions in the advance mechanism can yield "odd" advance curve behavior and need to be resolved before trying to establish a new curve.
Binding and/or mechanical restrictions in the advance mechanism can yield "odd" advance curve behavior and need to be resolved before trying to establish a new curve.
Last edited by 7T1vette; Jan 27, 2015 at 12:45 PM.
Thread Starter
Melting Slicks
Joined: Oct 2012
Posts: 2,156
Likes: 273
From: Dunedin NZ.
Thanks for the info. guys. I have already had a few goes at the advance springs in the dist and it seems to be running reasonably well (static advance about 15 deg, full advance 35 deg at 3000 rpm) except I believe that the vac advance is too much at idle (running manifold vac) because the idle is quite uneven unless you disconnect the vac advance, there is also some popping from the exhaust when descending hills unless I make the idle mixture richer, say about an A/F ratio about 12.3 to 1, I think this is too rich. Sitting at idle with the car in drive she does idle smoothly though. Was thinking of changing the vac advance can but my eyes were glazing over trying to figure out what to use!
So, I found an electronic unit that can replace both the mech and vac advance, will retain the stock dist (I have already rebuilt this)and can be programmed with several curves, I figured maybe this will be the answer as I can tailor the curves exactly to what the engine likes but retain a stock look.
Hence my asking for the original timing data because I would use this as a baseline if I get one of these units.
So, I found an electronic unit that can replace both the mech and vac advance, will retain the stock dist (I have already rebuilt this)and can be programmed with several curves, I figured maybe this will be the answer as I can tailor the curves exactly to what the engine likes but retain a stock look.
Hence my asking for the original timing data because I would use this as a baseline if I get one of these units.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If spending money is no problem, go for it. Otherwise, the vacuum advance cans are for different amounts of advance at idle vacuum. You need to know what your idle vacuum is and how much total advance you want from the advance can to make your selection. It sounds like you already have that info.
There are also "adjustable" vacuum cans that allow you to tailor that device to your particular needs. Lot less expensive (and less trouble) than figuring out a new spark box, too.
There are also "adjustable" vacuum cans that allow you to tailor that device to your particular needs. Lot less expensive (and less trouble) than figuring out a new spark box, too.
