Michael, and anyone else who can help,
The mysterious clicking from the rocker cover indeed appears to have
been
caused by something, presumably a rocker, striking the cover from
underneath. Here's what I have found so far:
I removed the rocker cover (much trickier than you might think with all
the fuel pipes over the top!), and there is a small mark on the inside
of
the cover in exactly the 'right' place that I pinpointed using the
brilliantly simple and effective screwdriver/stethescope trick Michael
describes below.
This seems to correspond to valve no. 9 counting from the front. From
inspection, and running it at idle with the cover off, the only thing
that seems possible wrong is that the top of the valve doesn't line up
perfectly with the rocker as it does on the other 11. There doesn't seem
to be
excessive lateral play in the rocker itself, at least compared to the
others, but it's hard to judge. What counts as excessive anyway? Does
this mean my valve is bent? Or something else?
Please help - I need to get the car back on the road as soon as possible
-
it's my only car!
Thanks
Paul
"Michael D. Porter" wrote:
> Paul Mitchell wrote:
> >
> > Sorry, yes it was. Any ideas?
> >
>
> A few, but not all of them may pan out. <smile> As others have said, you
> probably will need to pull the valve cover, but if you can tolerate the
> mess, it might be quicker to diagnose with it running at idle with the
> valve cover off, providing you can't locate the source by sound (while
> there are lots of echoes inside the valve cover, try the screwdriver end
> on the valve cover and handle in the ear trick first to see if you can
> pinpoint it that way). Several places to look come to mind.
>
> First, it could a rocker which is sticking--especially if the rocker
> bore or shaft is worn, so that the rocker gets cocked a bit sideways.
>
> Second, a weak or broken valve spring can cause the valve to bounce a
> bit, which then causes the rocker arm end to slap back and forth on the
> valve tip, especially if the valve head is sunk down in the seat a bit.
>
> Third, the clearance could be quite wide, but I generally discount this
> if it's intermittent--plus, you'd be very likely able to hear it above
> idle.
>
> Fourth, a slightly bent pushrod, so that the adjusting ball and the cup
> mismatch as the pushrod rotates.
>
> Last, it could be a lifter sticking, but it seems that would make a bit
> more noise than you describe.
>
> Try to pinpoint the area with screwdriver or stethoscope, if available.
> And if you don't see anything obvious with the valve cover off, run it
> at low idle and watch for something not moving smoothly.
>
> Cheers, Paul.
>
> --
>
> Michael D. Porter
> Roswell, NM
> [mailto: mporter@zianet.com]
>
> `70 GT6+ (being refurbished, slowly)
> `71 GT6 Mk. III (organ donor)
> `72 GT6 Mk. III (daily driver)
> `64 TR4 (awaiting intensive care)
> `80 TR7 (3.8 liter Buick-powered)
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