I'm trying to set my timing on my '72 based on BarryK's write up. I set the initial timing to 8* and checked that the centrifigal advance is not kicking in at idle using the rubberband method mentioned in his post. After removing the rubberband, I watched the timing as I increased the engine rpms. This was all done with the vacuum advance disconnected and plugged and I am using a dial back timing light. The timing went to about 24* at 2500rpm and did not change up to 3500 rpm. The centrifigul advance mechanism appears to be obstruction free when I have the rotor off and move it by hand so I can't see why its only giving me 16* (24* total minus 8* initial).

A couple of observations on the distributer:
1. Looks to be original. The car has well over 200,000 miles on it but the engine was rebuilt recently by the previous owner. The distributer has new points, cap, rotor, vacuum advance can (by me), and the advance weights and springs look shiny and new. The rest of it looks rusty and old.
2. When I originally bought the car, the initial timing was set to about 30* and the vacuum canister was disconnected (and had a hole rusted in it).

So, I'm trying to figure out where to go from here. I am wondering if it has the wrong weights on it. I'm also wondering if its worth messing around with this distributor or if I should be looking for a new one. Any thoughts/opinions?

 

is there a number on the distributor housing or on a band around the top of the shaft of the housing showing which model number distributor you have?
I have a chart that lists a number of distributors and what the advance curves and total mechanical advance amounts should be.
Some of the were only 14º - 18º total advance from the factory.
That MIGHT be your issue or it could be the springs you have installed, or a mechanical issue with the unit itself

 

There is a band around it right above the intake manifold with numbers on it but I can't get my head in there close enough to read it and my eyes just ain't what they used to be. Maybe I'll pull the distributor out tomorrow and see if I can read it then. On the very top (under the rotor) there is a plate that the posts for the springs are attached to. That plate has a number 183 stamped into it if that is any help. My wife is out of town and she took our camera with her so I can't take a shot of it. It really looks like the springs and weights are new while the rest of it looks really old.

 

How often due do you drive at idle? Idle specs only make sense for passing smog.

I have 36 degrees, all in by 2500 rpm plus an additional 16 in my vacuum advance. At idle, it runs about 16-18 centrifugal plus I have the vacuum advance connected. About 24-25 total at idle.

Read Lar's tuning paper at www.corvettefaq.com and go from there.

 

yukon
yep, the number of the distributor will be on that band