Re: Vaccuu gave test location

Posted by Owen_Dyneto On 2015/4/23 8:19:25

Measuring manifold vacuum via the port on the caruburetor for the distributor vacuum advance will not give a true reading. If you don't see a removeable plug somewhere on the manifold, then remove the vacuum line at the intake manifold going to the vacuum booster section of the fuel pump, insert a suitable fitting, and take your readings from there. An engine in overall good condition should show 18-20 inches of vacuum and rock-steady, no fluctuations of more than 1 inch or so.

Typically there is a screen mesh filter in the fuel pump and at the carburetor inlet.

Regarding your hesitation, if you can drive along at 50+ mph or so w/o problems, the hesitation at lower speeds isn't likely to be lack of fuel but it's a classic symptom of a leaking distributor vacuum advance diaphragm. You might also check your ignition timing if you haven't done so already. Easy enough to check the integrity of the diaphragm in the vacuum advance, just remove the line at the carburetor and with your mouth try to draw and hold a vacuum. Failure to be able to hold a vacuum indicates failure.