List,
I am asking for help in diagnosing a valve clatter for a fellow Wycroc member.?
His car is a 67.5 1600.? The noise is a fairly loud valve tick at idle.? It
appears to be most apparent in cylinder #1.? (We used a screwdriver as a
stethoscope and heard the noise in?the head, chamber #1).? Upon revving the
engine the noise frequency increases with rpm.? It is definitely an upper end
valvetrain noise rather than a lower end bearing thunk.
I have adjusted valves several times to different lashes and hear no
difference.? I have set lash to zero and still no change.? I have replaced the
rocker assembly with a good used assy I had in the garage and it made no
difference.? All cylinders are at 160psi compression.? Carbs are dialed in
correctly and the car idles well at 700rpm.? The noise started after a blown
head gasket was repaired and a valve job performed.? Owner states all new
valves were installed, seats cut by hand with a cutter (three angle cut on
seats), new guides installed and reamed correctly.? Seats were not removed when
the valve job was performed.? The head was cut .025" and the machine shop said
it had been cut once before.? So I'd estimate up to .050" has been removed from
the head.?
About the only thing I can think of is that one or more seats are loose in the
head, or a guide is loose, or the rocker shaft needs rebushed.? I didn't
measure the head thickness, but highly doubt a valve is hitting a piston.?
Has anyone encountered a similar problem?? Or can anyone offer some tech advise
on further diagnosis?? Owner hopes not to have to pull the head again but I am
afraid that it may be necessary.
Thanks in advance,
John Over
Denver, CO
67 2000
68 2000
71 240z
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