The Stovebolt Site Forums The Shop Area Engine Shop Points/HEI Advance Weights Compatibility

Looking for a reality check here. Are springs/weights from a points dizzy compatible with an HEI dizzy?

Working with a fresh '64 292 and finally tracked down an OEM HEI from a 70's 250. The 292 advance curve is retarded for longer before sweeping up to full advance very quickly thus preventing detonation at lower RPM's on the longer stroke of the 292 (this is a big bolt lugging motor, not a hotrod). The 250 sees advance earlier in the power band with a more linear application up the power curve. I cannot verify (my scale is broken) if the 292 weights are actually heavier than the 250. I have a points dizzy from the 292 and then the HEI dizzy from the 250.

I can verify that the 292 (points) weights fit in place of the 250 (HEI) weights, but the 292 weights look as if to give more total mechanical advance than the OEM 250 weights do. The 250 weights have thicker fingers vs the 292 weights which have thinner, thus allowing further centrifugal travel resulting in a higher top end advance. Intuitively, I would assume that the weights are not compatible without modification to prevent the excessive mech. advance, of which would defeat the purpose of using the weights as they would then be modified and no longer stock weight. The 250 and 292 have roughly the same RPM limit correct? Thus, both should have the same total possible mechanical advance, just differing curves?

I Have a recurve kit on the way for the springs as all the recurve kits I see are for v8's and I am assuming those weights are less desired than the 250 weights. Pairing the heaviest springs with the 250 weights "should do" for the 292. No amount of searching has been able to turn up OEM 292 HEI weights.

I've been digging the internet, Stovebolt, Inliners, etc for a few weeks and haven't turned up a solid answer. I've also been talking with Hotrod Lincoln and picking his brain as well on this topic. Figured I would post it up for others to chime in on and possibly help others in similar position in the future.

I have some opinions based on 40+ years of doing dyno tests on a variety of engines, marine, street, and racing versions. I'm not about to get into a fire hydrant watering contest with a few guys who have read a couple of Hotrod Magazine articles and can quote reams of internet searches, but if you'd like to discuss the matter privately, drop me a PM.
Jerry

Always appreciate the feedback Jerry. Our convo is continued in the PM's

Further observation from this morning with fresh eyes:

Given the difference in thickness of the fingers of the weights, it looks like the 292 points weights would allow a higher centrifugal travel when placed on the HEI vs the 250 weights, thus, a higher advance at the top end. Further inspection shows that the weights are spaced closer to the axis of rotation on the points dizzy and further from the axis of rotation on the HEI dizzy. Change in distance (further out) from the axis of rotation would mean that the 292 weights would allow advance quicker (the further from axis of rotation, the higher the centrifugal forces) on the HEI than they would on the points dizzy, assuming the same springs are used. Quicker is the opposite of what I am looking for however.

All of this to conclude: I assume that the weights between points dizzy and HEI dizzy are not necessarily compatible with each other, at least in unmodified form.

I am yet to find any info on actual mass of 292 HEI weights vs 250 HEI weights and if they do indeed differ or if it is purely the springs between the configurations that differ. The 250 HEI weights are labeled/engraved "60" for whatever that may mean. I also cannot find any data on the difference between L6 and V8 weights and compatibility. They look the same, but no-one can verify weight mass and it is my understanding (could be wrong) that OEM had different weights for different applications. V8 and L6, for lack of a better explanation, are very different.

Like many things, I could simply be over complicating a non-complex system. Use the 250 weights, put on heavy springs, and roll. Given its not a race car or dragster, I guarantee I wouldn't notice anything out of the ordinary, excluding pinging of course.

I use a dope dealer's digital scale to measure things like centrifugal advance weights and ammo reloading powder charges. A scale that measures down into grains and/or 10ths. of a gram is available on Ebay, dirt cheap. "We test, not guess!" like Sun used to put on all their automotive test equipment!
Jerry