Quote:
Originally Posted by gustafson
"Just gotta say, if this were the case (stuck valve causing crank to not turn), in over 50 years of wrenching, that would be a first for me. Valves tend to stick open, not closed, and don't prevent rotation. A stuck valve on an engine that prior to a starter change turned over OK? No, disregard that post, it makes no sense."
Agree
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Here is my thought and experience . Valves are just as likelyto stick up as down !!! If you have enough experience with engines to visualize this , here goes . The valve is stuck closed. The lobe of the camshaft is up against the lifter that lifts the valve . The valve is stuck and the lifter cai't move to lift the valve . You could watch with the pan off . When the engine is turned in the reverse direction , the lobe of the cam will turn back around to the other side of the lifter that cant move because the valve that it would lift is stuck closed . If and when the stuck closed valve or valves get unstuck . the engine should fully rotate again . Valves often can stick open . Stuck open valves cain't lock up the engine but does remove compression , completely from the effected cylinder . A tight engine can lock up easier . An engine with lots of worn in clearance wont stick as easily . I've owned and worked on model A's for 58 vears. I have had to un stick a lot of open and closed valves on model A engines as well as other engines , This is really common for older engines if they sit for long periods of time . believe it or not .