Before pulling the head, lets check a few items.
First, rotate engine till any intake valve, other then the bad one, is at full open position. Measure somewhere on the head to the top of the spring to get an idea how far its open. Do this for a few of them to see how they compare to the noisy one.
If the noisy valve is not lifting all the way, then check to see if the pushrod is moving as far as the others using the same idea as above. If you determine the lift is OK, then check to see if the valve is returning to the same height as the others.
If the lift is not correct, then the camshaft or a lifter could be bad. By pulling the offending pushrod out, you should be able to get the lifter out and check the face for wear.
Use a steel rule or a indicator if you have one for the measurements. If its a obvious problem, you will see it by these few checks.
Don't forget, the fuel pump is run off the camshaft and could be making noisy at the sametime the valve is opening. It might be worth your time to remove it before the head.
Joe
