HEI distributor springs / freshen up

[rajon]

I have an HEI distributor that I've had since the '80s and I don't know what it came from, originally.
It seems to be a Delco or whatever Chevys had stock.
But I've never been able to set the curve the way I understand that it's supposed to be done, and I finally got around to trying to figure out why. What I have is a distributor that has some really long slots in it that allow the centrifugal advance to move about 32 deg (crank rotation)
I looked and it doesn't appear to be modified or worn out in any areas, Unless someone who is a skilled machinist modified it, I'd have to say it came from the factory that way.
Do you, Cliff or anyone, have any inside info on whether the factory used a distributor with that much centrifugal advance for some application?
I have been setting it at 4 deg with the vac advance disconnected and then with the vac advance on manifold vacuum, that gives an additional 16 deg.

I also have read the post here on dist timing and I could use some OEM springs because what I get is full centrifugal advance at about 2300 RPM
So if springs can be had for that particular HEI unit that will give me full advance at a bit higher RPM, I'd like to order some.

Thanks

[Cliff Ruggles]

All HEI's have "long slots" but that doesn't control the amount of mechanical advance.

The advance curve is controlled by the center cam and weights.  The weights move out as RPM increases and stop advancing when the they reach the "flats" on the center cam, not when the pin reaches the end of the slot.

The picture below is from one I worked on recently showing the relationship between the weights and cam at full advance.

The factory design is excellent and the factory advance curves don't need much help either.

The aftermarket spring/weight kits are pure JUNK and will allow too much advance with little or no control of it at idle speed as they add some in making idle tuning difficult if not near impossible.

If you haven't done so already the shaft needs to be removed from the distributor to clean out all the old dried up grease, polish the shaft and associated parts and re-assemble with fresh grease.

Any rusted parts would need attention at that time as well.

HEI's have a bad habit of wearing out the pins and holes (bushings used on some) in the weights, so may need some work there as well.

I braze up the holes and re-drill them to resize them and provide a bearing surface. 

We offer a service to rebuild/restorer, recurve HEI's, which includes welding in a positive stop for the advance so lighter springs can be used.  Failing to do this will allow the distributor to add timing at high RPM which can be damaging to your engine.......Cliff