Hi Everyone,

I am fianlly getting around to working on this car. The motor is in MUCH better shape than I first thought. I bought a cheap-o aftermarket oil pressure gauge and got 6lbs at idle. On a suggestion from someone here who had trouble with the SAME gauge I bought a Sun Pro gauge and now have 46lbs at idle... So far so good.

BUT I have a valve tap sound that can be heard clearly through the right rear tail pipe. The car also has a rough idle. I pulled that side valve cover off to have a look, when the car is running everything moves and seems ok but I can hear the sound at the #2 cylinder exhaust valve.

With the car shut down, I layed a straight edge accross the rockers at the begining of the roller and they are all even except #2 - that one is about 1/4 inch lower than all the others.

This tells me that the valve is not shutting all the way. Any idea why? When I gave it a compression test ALL the cylders were between 150 and 152 even #2.

I would think if the valve is not closing that cylinder would have low compression

The car is a 454, with iron GM heads tat have been worked. Roller Rockers, hydraulic lifters.

When the car is running I can look down through the head (someone opened up the heads I assume for oil flow) into the valley and I can see that lifter is moving.

Any suggestions are appreciated!

 

First thing is to back off rocker nut and see if valve closes.

 

If the valve were even slightly open you would have very little or no pressure on that cylinder. Ideas-cam lobe worn, bent push rod, worn rocker etc.

 

 

I'm not going to flaunt any engine expertise, but the camshaft, lifters, push-rods and rocker arms only serve to open the valves, not to close them. If your valve is not shutting all of the way it looks to me like you have a restriction assocaited with the valve itself (bent?), valve-guide or possibly a broken valve spring. If I'm a left fielder with these suggestions someone please correct me.

I agree with DWncchs, I'd try backing the rocker-arm nut.

Mudbone64