GM HEI weird timing "curve"

While trying to set the timing on my little Cadillac V8, I noticed the timing actually would retard when the rpms went up! This is a GM HEI distributor with mechanical advance only.

Long story short, the rotor button almost jams up the advance mechanism. This used rotor button came off a non-advance computer distributor, so maybe there are different rotor buttons.

I will update after I get a new rotor button for a non-computer dizzy.

440shorty

Update: Bass ackwards??

Well, I got a rotor button for a "77 Cutlass with a 260 V8" which would be any non-ECU HEI distributor. It was different than the later rotor button. However, now that the advance works freely, it really retards the timing.

I checked a couple of manuals, and it seems to be assembled correctly. I tried heavier springs and different weights. Still works backwards.

I guess I will try flipping the weights and center piece and see what happens...

440shorty

update...

So far, I have found that the center piece can be flipped, but that only alters the timing curve' not reverse it. There was a reference to a "neutral" position of the parts in the articles I've been reading, which may imply that I am somehow on the wrong side of "neutral."

I did realize that I did not lube the shaft before reassembly, so I have to take the distributor back apart and properly lube everything.

Stay tuned, this might help more of us.

440shorty.

P.S. - this thing retards the timing like 20 degrees - the exhaust note changes as if the engine were laboring under load!

Sounds like you have a counter rotating marine distributor in there to me.