I was checking the timing on my '56 292. I'm running a recently rebuilt t-pot carb with a modification to run a single vacuum line to the vacuum advance. I have a distributor from a '62 Y-block and a single vacuum advance. When I adjust the timing with the vacuum line disconnected to the I think "3 deg" mark on the damper and then reconnect it after it's sets it runs poorly. It advances quit a bit with the line reconnected at idle. When I set it to the spec'd degrees with the line connected it runs much better, like it should. How much should the vacuum advance advance the timing at idle? It seems too much which is causing a poor running condition as specified in the shop manual.


~DJ~ AKA "Bleach"
1956 Ford Fairlane Town Sedan 30K original miles

Sorry I must have wrote it confusingly. The PCV is connected to the spacer. The vacuum advance is connected to a modified port on the carb  like the one done on Ted Eaton's page. https://www.eatonbalancing.com/2013/03/02/modifying-the-holley-teapot-four-barrel-carb-for-late-model-distributors/


~DJ~ AKA "Bleach"
1956 Ford Fairlane Town Sedan 30K original miles

3° BTDC ignition timing should run OK, and it should also run OK with vacuum advance connected, regardless. In this case it sounds a little like the vacuum advance diaphragm is leaking, but it's difficult to determine from just a description sight unseen.

20 or 30 degrees timing advance at idle would not be "too much" as far as that goes, something else is going on to cause the poor idle. For test purposes disconnect and plug the vacuum advance port on the carburetor. Set the initial timing to 12° and see how much manifold vacuum the engine is pulling. It should idle smoothly enough and drive OK as well. The mechanical timing curve is always sorted first, before connecting and messing with the vacuum advance.

Unfortunately I'm not sure how to check the mechanical advance. I recall there was a machine in my high school back in the late 70's that would check the advance. We were never shown how to use it.





~DJ~ AKA "Bleach"
1956 Ford Fairlane Town Sedan 30K original miles

It is very doable to use the engine itself as a kind of distributor machine for careful tuning. Basically just involves disconnecting and plugging the vacuum advance port, and then run the engine up through the RPM range and observe the mechanical ignition advance using a timing light. You can tell a fair bit as well about the mechanical ignition condition and timing set wear simply by looking at the way the numbers appear under the strobe, the way they react going up and down. A lot of the parts we use today are just plain worn out, a good "tight" serviceable distributor really makes a difference in how smoothly it runs.

Ford type distributors are not generally known for their ease of adjustment should it be necessary and Y-Block distributors in particular are not exactly conveniently located, back against the firewall like they are. So there's a lot to be said for avoiding the hassle and sending it off to be checked out and curved on a machine for the application intended. On the other hand it is very gratifying to have "done it yourself" and really learning a lot more about how a good sharp engine tune is achieved. As always the shop manuals and publications have the important details that are sometimes overlooked.

I have the same machine (plus the tall manometer needed for accurate Loadomatic setup).  Good thing I also have the operator manuals, since it’s been so long since I used it, I will likely have to study them at length before calibrating another distributor!



6 VOLTS/POS. GRD. NW INDIANA

The '62 292 y-block distributor with mechanical advance curve appears to be rather wimpy compared to a '57 292 distributor with mechanical advance.

11 deg. @ 2000 for '62  @ dist
17-18 @ 2000 for  '57 @ dist.
Then you double it for at the crank

The 62 version would be more desirable to me.. That way you can give it 12-14 degrees of initial advance for a nice idle and throttle response and the 22 degrees in the distributor gets you right where you want to be for total timing