Thread: setting valve lash

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Make sure the feeler gauge is dirt and oil free as well as the rocker tip and valve stem tip. You should be able to lift up on the rocker tip with your thumb and forefinger at the valve tip to take out the play at the pushrod/rocker interface and insert the correct feeler gauge or stack of gauges with just a slight push. They shoudn't go in loose, but you shouldn't have to force them either. Always use the thickest blades you can make a combination with. For instance, if you were to need 0.025" and there was no 0.025" blade, use a 0.012" and a 0.013" stacked together rather than a 0.020" and a 0.005". The thin blades will want to bend and curl up on you where the thicker blades will hold their shape.

The feeler gauge blades should have just a very light coat of oil on them. Wet your finger and thumb with oil and draw the blades through your finger and thumb to wipe off all but just a very, very light coat of oil, wiping your finger and thumb on a lint-free rag as you prepare the blades. Remove dirt and grit from the rocker/stem tip interface by drawing strips of paper through them as you hold the rocker tip down against the tip of the valve stem. Just cut up some strips of white paper about the same size as the feeler gauge blades. That'll remove all the grit, dust and oil from the interface so you can get a good reading. Be careful when tightening down the lock nut. If you don't have someone holding a tool on the adjusting screw to keep it from turning, it can tighten up as you draw the lock nut down.

Oh yeah, and don't forget to squirt some oil on the valve stem tips before you hit the starter.