[MescaBug]

Looks like I dont have any, or very limited mechanical advance following a cam swap.

Engine break in went very well. Set my initial to 12, two 10 min runs, changed the oil and filter, oil was very clean, no residue/shavings. No vacuum leaks, everything works like it should. Purrs like a kitten. Except...

Took the timing light to set the correct timing after cam break in, re-set to 12 BTDC without vacuum advance, adjusted the fuel mixture and idle speed.

My wife was in the car, asked her to rev up to 2000rpm, no advance. 2500, no advance, 3000 no advance. I was like, what the hell. Maybe 2-3 degrees...

That's with a working HEI with 349 centerplate and 139 weights. Typical. Changed for heavier springs, thinking maybe too light or worn springs would already advance timing at idle. No change. Went to the lightest springs I have (RED), no change. Rotor is moving freely, no binding. This HEI was completely rebuilt about 1100miles ago.

Swapped for a points distributor with a Pertronix Ignitor, re-set the initial, rev up to 3500, no advance. Swapped for a points distributor, no change.

Traced a line on the balancer to see if its slipping, its not.

I'm at a loss. What can cause 3 different distributors to not advance timing?? I should ask, what else can prevent mechanical advance?

Any help/advices would be greatly appreciated.

[skipp65]

Problem with timing light???

[MescaBug]

Originally Posted by skipp65

Problem with timing light???

I didnt think of that. Good call, lol. Never had a timing light failed on me, but i guess it can happen.

[neill]

If the timing can be changed by moving the distributor then it can be changed by the movements within the distributor.

[Schurkey]

Advance mechanism assembled incorrectly?

[steve25]

If it is a used HEI then it by far would not be the first time that the inner advance shaft was so gummed up by old dried up lube that it can not move, which will make for little to no machincal advance if it's stuck in one position, or stuck the other way will not allow the mechanical advance to drop back down with rpm.

[MescaBug]

This HEI unit was rebuilt last summer. It moves freely, everything was cleaned, lubed and reassembled. Same for the 2 standard distributors I tried.

Very odd. With the 1112121 points distributor, manual says it should start advancing at 1400rpm, then 10 degree @ 2400, and 24 @ 4600. So with light throttle, timing should be +- one inch before the 12BTDC mark. It barely moves past 2500rpm.

I will try another timing light just to be sure that's not the problem.

EDIT: The vacuum advance works though.... I plugged it with the engine running. The rpm jumped a bit and I saw a few degrees advance. That's what the HEI.

[MescaBug]

Did some more tests: Problem seems to be the tach I'm using for these tests... Looks like its off (high) by as much as 500rpm. Didnt had the time to re-install the original dash tach wire, so I used an Auto Meter tach.

Wife was starting and revving the engine, I was under the hood with the timing light, a feet away from the fan and noise, you think its revving a lot, when its not. Cant blame her though, she drove the car maybe 2-3 times...

I started the car to do more tests, I knew right away the tach was off. It was idling fine, tach was showing 1500rpm. So when we thought we were at 2000rpm, expecting at least 10-12 degrees of advance, we were actually at 1400-1500rpm, just when the advance is suppose to start.

I hooked up my dash tach to the coil, idle was at 900-1000rpm. Will check the timing tonite and post the results.