set timing

[johnpaulny]

I set the timing because there was pinging when the engine was under load - uphill, accelerating, etc. It worked, no more pinging. However, I subsequently learned that you're supposed to disconnect the distributor vacuum line when setting the timing. The line on mine is the original metal tube. I disconnected it right at the vacuum advance on the distributor. If I'm correct the vacuum should be blocked, but I'm not sure where; should I block the vacuum advance connection point or the tube leading to the carburetor? Also, is it necessary to use a tachometer when setting timing or is it OK to just let it warm up to idle? It seems to idle at a reasonable speed judging by ear.

 

[Yadkin]

When you disconnect the vacuum line you need to plug it to keep air from entering the vacuum source. So the way you did it, plug the tube.

Going by the book, you should use a tachometer.

All that being said, most classic car mechanics set the initial ignition timing "by feel". The main reason is that the crankshaft dampers have rubber between the outside ring and the inner ring. The design is for harmonic balance. After 50 plus years the rubber deteriorates and the outer ring slips relative to the inner. Once that happens the numbers on the ring mean nothing.

The second reason is that the factory settings are on the conservative side, for gasoline sold back in the day and for compression that the engine had when new. Typical factory numbers are 6 degrees BTDC but 10 or slightly higher is typical.

Best to advance the timing by trial and error. Use your timing light to verify the the distributor vacuum and mechanical advances are working smoothly and properly. With the vacuum disconnected, the mechanical advance should star to add after 1200 RPM and increase smoothly with increasing RPMs. Vacuum advance should add 15 to 18 at idle, and drop to zero additional when you "blip" the throttle.

To time by trial and error, keep the vacuum connected, advance the timing, test drive the car, and keep adding until it knocks under uphill acceleration. Then back off 2 to 4 degrees and be done with it.

 

[johnpaulny]

thank you, very comprehensive answer.