ZD Problem

[Justin]

SO I finally got my regulator problem fixed and finally got the zd running for the first time. It had good compression but only ran for about 30 seconds then quit do to a lack of compression. The intake valve was leaking. I don't know why as I had already (about 6 months ago, and never ran engine) had the exaust valve seat ground and I laped the valve to it. I also laped the intake valve while I was at it. So I laped the intake for a second time. After this the engine has absoultly awsome compression. It ran for about 15-20 minutes then died from lack of compression. This time the exaust valve was leaking. So again I laped the exaust valve. I didn't get very much compression(almost none). However the engine runs. Now my question is why is this happening?? Is it something to do with the fact that I am running the engine on lp?? It only runs at about 80-100 rmp's pulley speed. Anyone got any ideas whats wrong or how to fix it??

Thanks Justin

[Chris Kirk]

Justin -

Did you make sure to adjust the clearance between the lifter "wedge" and the valve stem? Remember that when you lap in valves, they always drop deeper into the seats a few thousandths of an inch, which closes up the clearance between the valve stem and that lifter wedge. If you have not properly adjusted the valves after lapping, the clearance is probably too tight, and when the valves heat up, they expand enough in length to hold the valve open enough to loose compression. When the engine cools down and the valves contract, the compression returns because the valves can once again seat properly. Try adjusting your valves and see what happens. Just a thought.

Chris

[Justin]

That was my problem, I went back out after the engine had cooled of and sure enough it had lots of compression so I adjusted the amount of shims in the tappets. Thanks for the help. Justin