Hope I'm not boring the list with my updates ;^)
I have found the problem. I am not the first to get the head off in
44 years. This TR4 has valve seats installed, I'm guessing for
unleaded fuel. The issue I now have (slapping tappet noise, low
compression on one cylinder) is that one exhaust valve guide is over
size. My 'bad' valve was due to the opportunity for this exhaust
valve to flap laterally, I think. It slides sweetly in the other
three guides. In this visibly bigger guide, it's all loosey goosey -
inverted, as when grinding the valve and seat, if I lift the valve
1/8 inch, its lateral movement is 3 to 4 times that when in the other
exhaust guides. Other exhaust valves behave similarly, i.e., its an
odd guide, not an odd valve. I guess in the work above someone got
distracted and didn't finish the job. There are no signs of distress
to indicate a drift couldn't get the guide out.
I do not have the equipment to measure accurately, but I'm puzzled by
the descriptions in the relevant catalogs of 3/8 to 5/16 conversion
guides, if that is what happened previously. I've a good eye for
sizes (spanner - nut). To my eye, the difference is more than 1/16 inch.
Enough, today.
Cheers all,
Brian
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