Originally Posted by ap72
a bad module CANNOT advance timing, though it can slightly retard it.
I'm wondering if you either have a bad advance mechanism, or just don't know how to set timing. you said "locked out" and locked out is locked out, that means 34º at idle, at redline, and at every point in between.
The timing wasn't locked-out when the car was on the chassis dyno. On the chassis dyno, the timing was set-up for around 14* initial + recurved (medium springs) mechanical advance, supposedly all-in by 3,000rpm. Vac advance was disconnected for all pulls. Prior to going on the chassis dyno, I had checked the timing with a xenon timing strobe and verified 34* total @ 3,000rpm and took it to around 3,500-4,000rpm to make sure it was all-in... the timing didn't advance any further, so I didn't take it any higher. The oddity is, on the chassis dyno, the operator of the timing light was saying it hit 50*+ at the top end of the RPM range, which I just don't understand. I'm starting to think that maybe he set-up his fancy timing light up wrong, or was just somehow mis-reading it. Having said that, the guy tried a different light and got the same result.
When I was talking about locking the timing out, I was referring to a time well before I went to the chassis dyno when I was experimenting with different set-ups.
So, as long as the initial is correct, how can a mechanical advance mech add timing beyond its design limits? The amount of mechanical advance is limited by the length of the slots in the base plate and this is all stock GM HEI. I believe stock HEI distributors add around 20* mechanical. To get into the 50* range, the distributor would need to be adding at least 36* to the 14* initial and I just don't see how this is even possible.
Finally, with 50*+ total timing on a WOT pull with the hood up and standing right by the motor, surely it would be rattling away and it would be very obvious. When I've had the timing too far advanced on the past, I can even hear rattling from the driver's seat when driving the car out on the road.
Unless anyone had any 'magic bullet' explanation, I can only assume the operator somehow misread the timing?