Reply to "Ignition, vacuum advance question"

Mikael,
I'm no expert but have been messing around with my dizzy the last few weeks so here goes.
First off the vac reading is to low for a stock motor, if it's been modified with a hot cam then it could read lower than the 18in. normal reading but if your running the 600 carb than I assume it's fairly stock. Is the 14in. at idle and manifold vac? Do you get the same reading cold or hot engine? Is the needle steady or drifting, pulsing, vibrating?
Here's some general info on low vac.

Low vacuum readings may indicate intake valve, manifold, or carb gasket leaks including internal or external manifold leaks. Spray carb cleaner around suspected areas to test for leaks.
Plugged catalytic converters, stuck heat riser valves, plugged intake crossover heat passages, crushed exhaust pipes, plugged mufflers, (check out that mouse nest in the exhaust!), and similar restrictions will usually lead to very low vacuum readings.
Excessively carbon in engines or those that did not get their oil changed often enough may result in sudden vacuum reading changes when valves stick. It could happen at any engine speed and may temporarily cure itself by quickly changing engine speeds.
Lower vacuum readings directly related to engine misfiring may be a result of a burned exhaust valve.
Constantly changing vacuum readings at low engine speeds may indicate a problem with worn valve stems, guides, or seals. Higher engine speeds tend to temporarily cancel out this problem.
High-speed vacuum readings that change may be a result of broken or tired valve springs, while low engine speed vacuum readings tend to be constant.
High performance or race cams tend to result in lower vacuum readings.

The burnt exhaust valve is high on my list.
Do a compression check on the cylinders.
Cowboy from Hell wrote:
My advice is that you do not need a timing light. Start by connecting the vacuum advance to ported vacuum. Leave the vacuum retard disconnected. Loosen the distributor locking bolt enough to allow adjustment. Start the motor, let it idle, once up to operating temp, slowly rotate the distributor in the advance direction. (clockwise). As you rotate the distributor, the idle speed will increase, continue to slowly rotate the distributor until you just reach the point where the idle speed stops increasing. This is the ideal advance setting for idle, and it will be significantly different than the specified setting from Ford. Ford’s setting was derived to meet emissions, it never was an ideal setting. If you’ve modified the motor in any way, the oem setting no longer applies anyway.

I think I'm at 18in BTDC. Your description off idle sounds to advanced.

If you have a dial back timing light see what your advance is at the 1000(0 advance), 1500, 2500, and 3000 (all in?)RPM speeds.

Steve