On a 4 cylinder engine #1 and #4 are at TDC at the same time but.....
Doesn't have to be at TDC. Just has to be fully closed. If the adjacent
valve is wide open it usually will be. I normally adjust the ones that have
clearance, mark them with chalk as I adjust them, turn it 180°, do it again,
and keep on till they are all marked. Then I go back and check to make sure
none have more than the right clearance (in case one was not quite all the
way closed when I adjusted it before). I sorta integrate the setting and
rechecking along the way. I realize that is not the most efficient in terms
of engine motion but it seems to be in terms of my time. I set mine to 0.020".
Some guys like less but I have burned B30 exhaust valves with less in the desert.
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George Downs Bartlesville, Heart of the USA!