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 HEI centerplate advance curve / slope 
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Joined: Sun Aug 04, 2013 11:02 am
Posts: 44
Does anyone have information on the advance rate for the various centerplates used in HEI distributors. I do know that info is available for the total advance the various centerplates provide but I'm looking for the actual increment in advance as the weights act on the centerplate thru the RPM range. I do not have access to a distributor machine. And I realize I could use the degreed damper to find the curve but was hoping to find someone with a chart with the plate numbers and the actual curve provided by the different plates.

I have one extra plate to play with and grind. Looking to achieve a linear curve to add 20* that starts at 1500 RPM and is full in around 3300 - 3500 RPM.


Thu Aug 06, 2015 9:11 pm
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Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
I don't know of such information about rate. There is a list in the Chevelle Forum of cam numbers and amount of advance but not advance rate, as far as I have seen. What numbers on the plates and weights you have? Spring wire and coil diameters, number of coils - full and half turns (4.5, 5, 5.5 etc.) and inside length of spring eye to other eye. Can you post a picture of what you have?

Fri Aug 07, 2015 12:55 am

Joined: Sun Aug 04, 2013 11:02 am
Posts: 44
I have seen the Team Chevelle listing of centerplates, weights and degree information. Helpful, but not quite enough.

In the dizzy I have a#368 plate and #106 weights with a pair of Moroso silver springs. The plate and weights are original to the distributor and should provide ~20* at the crank according to the Chevelle info. Haven't checked the RPM curve but I do know they are not fully in until around 4000 RPM.

I have 2 extra centerplates - #370 & #406, and 2 weight sets - #139 and #130. For springs I have the original set that went with the 368 plate and 106 weights. Measurements are: 4.5 coils, .030" wire, ~250" diameter of coil, .180" length of coil, overall length (outside of eye to outside of eye) .650" to .660".
Other springs are: 5 coils, .030" wire, .230"diameter of coil, .200" length of coil, overall length.655" to .675".
Will need to pull cap and rotor to get the Moroso spring details.

Have seen a Pontiac site that suggests grinding the centerplate to achieve an ideal curve but it seems like a distributor machine would make that task much easier. Not that lucky.


Fri Aug 07, 2015 3:38 pm
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