Vacuum Advance
Posting Guru
Joined: Feb 2002
Posts: 2,404
Likes: 3
From: Cleveland, WI USA
Vacuum Advance
Hi all,
I want to make sure my VA is working and I'm not sure how to do it. Don't laugh, but I tried sucking on the vacuum hose and it did nothing. I can move it with my finger, but it's hard. I mean, it moves freely, just feels like strong springs.
It's a 460 w/a Holley 750, and the vac comes from the carb.
If I remove the cap and have someone turn the engine over, should I see it advance?
How else can I test it?
Thanks in advance!!!
Kevin K.
I want to make sure my VA is working and I'm not sure how to do it. Don't laugh, but I tried sucking on the vacuum hose and it did nothing. I can move it with my finger, but it's hard. I mean, it moves freely, just feels like strong springs.
It's a 460 w/a Holley 750, and the vac comes from the carb.
If I remove the cap and have someone turn the engine over, should I see it advance?
How else can I test it?
Thanks in advance!!!
Kevin K.
Moderator
Joined: Jan 2001
Posts: 56,949
Likes: 2,718
From: Virginia
Vacuum Advance
Hook up a timing light. Run the engine just above idle speed. Pull the vacuum line on and off. You should see the timing jump everytime you put the vacuum line on. Or if you want to hook the vacuum line to manifold vacuum, you could leave the engine idling. Everytime you take it on and off manifold vacuum, the idle should change and the timing will jump with the timing light hooked up.
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