I've got a newbie question about vacuums

[Anonymous]

Hey everyone...I was just wondering if anyone could point me in the right direction about vacuum and vacuum advance and all taht jazz, as it kinda confuses me. Also, i would like to know how to test my vacuum to see if that could be causing some shakiness in my idle. Not sure if you need this info but here it is

Stock I6 200 in a 65 mustang
The only thing thats been put in it is the petronix ignition and the 40k coil
its got the old 1bbl autolite carburator, i'm pretty sure its the autolite 1100

Main thing i am trying to find out is how i go about testing the vacuum, where i can test it, what i need to test it (i have a vacuum guage but not sure what i need for hoses or other attachments) and what some numbers should be...i understand that the vacuum can help diagnose some problems, and i think this is the only route that i haven't taken yet. Thanks for all your help ahead of time

Sean

 

[wsa111]

Sean, what pertronix do you have in your distributor?? If its the pertronix II that could be your problem with a rough idle & will even cause cutting off. If so go the pertronix I and possibly your rough idle will be fixed. Did your engine just develop this with the installation of the pertronix if it is a II ?? Advise William

 

[Anonymous]

nope, i have the pertronix I installed. i installed this last summer and since i have installed it, it has been running fairly well. i've done just about everything and i think i'm down to the last choice of switching out my carb/distributor to something a little newer and getting rid of the load-o-matic that i guess i have...that stuff is still kinda sketchy in my head but i've been reading up enough as to where i think i could handle it

 

[66 Fastback]

Get a vacuum gauge. I think Autozone and most places carry them now. I bought one from Sears years ago. Or you can buy a Mity-Vac pump with a gauge. You'll find lots of use for the pump. For diagnosis of engine health, you need to connect to full manifold vacuum. My '66 had a plug and a port on the passenger side in the intake manifold. Get a pipe thread to hose barb connection. Keep in mind that a common cause of low engine vacuum is insufficient timing advance at idle. A functioning vacuum advance should speed up the idle and smooth it out once it is reconnected after setting the initial timing.
Doug