Is my thinking correct that to disconnect the distributor vacuum advance in order to connect a vacuum gauge,the only way to do it is to remove the fitting in the base of the carburetor, at the throttle body?
You can disconnect the vacuum line from the advance at either end. Just make sure to plug it up. Where are you connecting the gauge? Are you disconnecting it to set the timing or just check manifold vacuum?
Otto,
I would be disconnecting it to set the timing, or to time the engine with a vacuum gauge.
When setting the timing, You can disconnect the vacuum line to the advance at either end. Just be sure to put a rubber plug in the line or the fitting at the carb to keep it from sucking air while you're making your adjustments to the distributor.
Folks,
If one is going to hook up a vacuum gauge, it is not done at the carburetor fitting - wrong vacuum.
One needs to get the vacuum reading at the manifold, not the carburetor (we can discuss this if anyone is interrested).
Use the fitting for the windshield wiper motor.
Tha's my story.
John W
It depends on what you are trying to do. I’ve teed off the vacuum advance line to check the vacuum advance curve verses vacuum.
I don’t do it that way anymore. I use a hand vacuum pump now. No worries about the mechanical advance affecting the readings.
Glen
Quote from: Glen on May 24, 2010, 12:56:27 AM
I use a hand vacuum pump now. No worries about the mechanical advance affecting the readings.
Glen
Glen, care to explain the procedure? I ask, as I do have a vacuum pump. Where would one connect it?
I connect the hand vacuum pump to the vacuum advance unit in the distributor and plug the line going to the carb or manifold. With the engine running at idle to prevent the mechanical advance interfering with the test, and using a digital timing light, I slowly pump up the vacuum pump. Comparing the vacuum gage on the pump and the timing mark on the harmonic balancer I can check the vacuum advance curve.
Using this technique I discovered that the vacuum advance units I buy from the parts stores are going well beyond the 12 degrees advance for my 68 ELDO. I installed a plate to block the VA from going beyond 12 degrees and I no longer have pinging at a steady pull up a slight hill.
Glen