Hey Guys,
We are in the process of rebuilding the top end of an engine that missed a shift in which the pistons and valves became real good friends. The head has been rebuilt and we assembled the top end last weekend. On initial startup the engine ran for about 3 seconds, next crank it coughed, and on the third crank it just spun. And by spun I mean a nice smooth sound with no associated resistance. Based on the sound we decided to go ahead and do the compression test to confirm. First spin we got 50 on #1 and then 0 on the next 3. Timing was at TDC on Cam and Flywheel.
The next day we took off the intake and made sure the valves were moving, a few minutes later we took off the came tower. We then blew compressed air into the cylinders since all the valves should be closed when the cam tower isn’t on. Perfect compression.
Later we noticed the exhaust valve stems were protruding 1/8” higher than the intake valve stems. On another head we had in the shop they were all level. Fast forward a week and the head is back with all valve stems flush. We put everything back together and the same scenario played out. We spun it over a few times with no spark or gas to build some oil pressure and the compression was there. On initial start up the engine ran for 3 or 4 seconds. After that the engine just spun again.
It seems to us that everything is ‘ok’ until the lifters pump up after which they are somehow keeping the valves open on the compression stroke. Again, we used the same cam tower that came off the car and the flywheel and cam are at TDC. Any thoughts or has anyone ever had this issue?
Thanks!
