Timing

[Duke W.]

Re: Timing

Got back to the car today.

The distributor has 21 degrees of advance at 900 rpms and 31 degrees at 3000 rpms. These readings were taken with the vacuum advance disconnected. The readings were done with a dial back timing light. The readings are steady at 3000 rpms. They jump around 2-4 degrees at 900 rpms. I'm going to remove this distributor and substitute it for another one. I'll send that other one out first for calibration.

Big concern is the lack of vacuum. I mean the gauge reads only 2-3 inches of mercury. Hardly moves off the stop. I either have the mother of all vacuum leaks; a bad gauge; or, I'm not getting a signal from the port in the back of the carburetor.

I'll have to come back to this later. I have other responsibilities for the next week. Thank you for your help with this.

Your data doesn't make any sense. The centrifugal should have a start point, usually between 700 and 900 RPM and a maximum point. I believe the OE '62 340 HP curve is start @ 700, 24 @ 4600, but check your ST-12 and AMA specs.

Does the engine still have the original 3269S AFB? Since the engine was not originally equipped with vacuum advance, I'm not sure if the carb has a port to supply manifold vacuum to a VAC.

Also, you have still not reported and estimate of shaft end play and side play. Most OE distributors were assembled with way excessive end play. The spec in the 1963 Shop Manual is two to seven thou, but most are in the range of 40-60 thou, and this is the major source of spark scatter.

As Joe said the engine would likely not even run at an idle vacuum of 2-3" Hg. It's likely that the port you are testing is not reading full manifold vacuum. Also, the vacuum gage must be attached to a proper manifold vacuum source with a "tee" for a parallel connection. A common mistake is to remove the hose from the VAC and attached it directly to the vacuum gage, but this is incorrect because you have changed the engine configuration by eliminating the vacuum advance, which will cause loss of RPM and vacuum.

Duke