My dial back timing light is a Sears that is also sold under the Acton name. I don't know what Autozone sells.

The M103 balancer is marked to at least 40 degrees BTDC IIRC, and it can be read with a conventional timing light, but I find it much easier to use the timing light dial to turn the balancer notch back to align the 0/T mark on the balancer with the timing tab and then just read the dial on the light.

I've only researched the EZL operation on M103 engines. The V-8s had very similar systems, but I can't say for sure whether the 4.2 had vacuum advance at idle or not since I have not reserached it.

Go to the following link:

http://www.peachparts.com/shopforum/showthread.php?p=833484#post833484

In this thread I reference another link with results from the timing tests on my car that I conducted earlier this year.

I will also add the following caution. Further reserach indicates that the EZL alters the timing map - not exactly sure how - if the coolant temp exceeds 95C, and some of my data was with temps over this value, so I need to do some retesting will coolant temps under 95C.

Duke