1972 LT1 Tapping noise
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Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
1972 LT1 Tapping noise
I am attempting to troubleshoot my none operational headlights. As I was doing this I thought I would check what kind of vacuum I have during idle, before I started on anything I Pinch the vacuum line coming from the manifold, when I pinch it probably restricting anykind of flow or vacuum I would hear a tapping noise from the right bank toward the rear. When I let the tube go the noise would go away.
I called the previous owner and asked him it a cam was installed in the car. He confirmed my assumption, so I am thinking during the cam installation the proper clearance on the rocker arm was not established.
The car barely have any vacuum during idle. I am concern about the tapping noise when I pinch the vauum tube.
I called the previous owner and asked him it a cam was installed in the car. He confirmed my assumption, so I am thinking during the cam installation the proper clearance on the rocker arm was not established.
The car barely have any vacuum during idle. I am concern about the tapping noise when I pinch the vauum tube.
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
Unless the PO exchanged the original cam for one of the hydraulic variety you should be able to eliminate the "tapping" sound by correctly adjusting the valve lash to the proper specs, generally somewhere between .020"-.025". Since the valvetrain is completely mechanical and not related to any of the vacuum systems on your car, pinching the main vacuum line shouldn't have anything to do with any 'tapping' sound. If the camshaft that you have has a lot of overlap, i.e., if it's ground such that the intake and exhaust valves are open simultaneously for a significant amount that would explain (at least partially) the low vacuum at idle. I would first check the valve adjustment and make sure that is correct, then plug the vacuum tap at the intake to see if you get a significant increase in idle vacuum. After that you can begin tracing back through the headlight and wiper door systems to try and locate any leaks.
Last edited by birdsmith; Jan 16, 2011 at 08:52 PM.
