VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 How do I check if the vacuum advance is working?

I am still having trouble with hesitation from a standing start. I advanced the timing, which helped a lot but the engine knocks on acceleration. I backed off on the advance but the hesitation got worse and the knock is still present.

Should I see the distributor rotate when I "gun' the engine?

I doubt that the vacumn advance has anything to do with hesitation from a stop, nor about the engine knock.

To answer your question: yes.
If you have a rod knock, forget about trying to fix anything until you get that fixed or replace the engine. I think if you pull off one plug wire at a time and the knock goes away, you will have found your bad bearing. You may be lucky. I'm not sure if your engine still had the bearing shims or not. Some of these guys can tell you stories about swapping the bearings out or just shimming to get rid of a knock. I don't know the story of your car, but rebuilding yours or finding a good replacement is not that big a deal. Lots of guys get rid of the stock running gear to hotrod our cars.
Plenty of guys here can give you more help than I can.
Good luck!

When you say "knock" ... are you talking about a "spark knock / ping " or are you talking about a knock, such as an engine bearing problem ?

I think it is a spark knock/ping.

Use a hand held vacuum pump .... connect to the vac. advance .... see if it will hold vacuum or not. If not, diaphragm in advance is leaking.

Actually you can put a rubber hose on the vacuum advance and suck really hard. If the link does not move (some times you have to push in on the link lightly) they you have a leak. If the link moves put the end of you tongue on the end of the tube to seal it off. If the link returns to the original position then you have a small leak. If does not move for 30 seconds or so the advance is okay.

I like your diaphragm leak-down test method , Chipper , it helps me " bond " with my car...How long will the circle on my tongue last ? Thanks , Kevin

Depends on how hard you can suck and the size of the hose.

To check the advance run the engine at a fast idle. Then disconnect the vacuum line while the engine is running. . The distributor should return to the same position it is in when the engine is not running.

This all sounds like the beginning of a "R rated" story !