General Category > Quadrajet Carb Talk and Tips
HEI Distributor mechanical advance curve options
Cadman-iac:
--- Quote from: Kenth on April 10, 2026, 03:02:49 AM ---Here is some info that might be helpful:
--- End quote ---
Yes, those might prove useful. Were your tests done on a Pontiac distributor with a ccw rotation, or a Chevrolet with a cw rotation?
Thanks Kenth.
Cadman-iac:
Ok, just a bit of background info here, after doing all of my testing using the angle protractor to determine what the centrifugal advance each combo of plate/weight I've got on hand will yield.
Remember i mentioned that the actual engine testing results were not the same as what I got on the bench.
But comparing my bench results with the list that Kenth just posted, the differences are very slight.
For 1 example I've tried on the engine, Kenth shows that with a 370 center plate and number 139 weights, he got an advance of 25°.
On my bench test, using the same plate and weights, I got an advance of 26°, which is just 1° off.
However, on the engine, this exact same setup yielded only 20°, even when run up to as high as 4000rpm, falling short by 5 or 6° depending upon who's results you use.
What gives? I realize that the springs can have an effect on both the rate of advance as well as the total available advance, I think. Is this correct?
The next question, where would you get new springs that are not Chinesium garbage?
I have multiple sets of springs, and there are differences such as the number of coils and the diameter of the wire itself. I'll try using the smallest ones I've got to see how it affects the total available advance. This may be what I've been overlooking in the past. Any ideas?
Rick
DJD OLDS 4MC:
Please refer to attachment.
Hope it helps!
DJ
Cadman-iac:
Yes, this helps. I'm guessing that your readings are in distributor degrees because of the small numbers shown.
I'll try to get some pictures of what I've done some far as far as the test distributor. Im also using an old drill press adapter, meaning it's a fixture that holds a portable drill in order to turn it into a drill press. The distributor will sit at the top mounted above the drill itself. Then it’s just a matter of outfitting everything that would turn it into a distributor tester.
Rick
DJD OLDS 4MC:
Glad to help.
Yes, the advance numbers are in distributor degrees.
Looks like you'll need to find some different centerplates if you're going to hit your 24 degree target.
Good luck!
DJ
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