Timing curve for my big-cam 451?

Finally had a chance to work on it... very strange findings.
I had another vac can (9L, or 18 degrees) and tested that with a Mityvac hand pump. Sure enough, with the adjustment full CW, it barely moved at 5", about 10 degrees at 8", and full 18 deg at 12". :)

So I removed the existing can (8L) and installed the 9L. There is a little slack in the reluctor plate and it doesn't actually start to move the plate until 6-7", all in by 12".

Started the engine and got it warmed up... noticed the idle speed was a bit faster. My timing light showed it idling at 39 deg now, rev in neutral up to 50 deg. I readjusted the idle speed slightly and disconnect the vac hose, idling at 28.

With the hose still disconnected, I gradually increased the rpm and it only got to about 33 and then began to retard! :eek: A quick fast rev and it dropped to 31... on decel came back up to 33 and then down to 28 at idle. I expected the high rpm retard from the electronics, but what happened to the 35 at 4000... ?

Even more strangely - I tested the 8L can I'd removed and it also started to move at 5" and was all-in by 11". WTF. There has to be something binding or moved in the mechanical parts... Time to take the dist apart and clean/lube. Maybe reconfigure to an initial of 22-24 with two medium or heavy springs as suggested, as long as it doesn't start advancing at my 1200 rpm idle. Definitely will need the vac can to keep the idle timing up then.

Would be nice to have a distributor machine in my shop about now :rolleyes: