View single post by Esprit2
 Posted: 04-14-2006 12:51 am
PM Quote Reply Full Topic
Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 573
Status: 
Offline
 True,  grinding/ lapping the valves will result in them receding into the head,  getting closer to the cam, and closing up the clearances.   Proper clearances will always go away during the process.

And the machinist should check the valve stem height and grind it to keep it within spec.   However, no machinist is going to try to hold valve clearances by grinding valve stems.   It's just not practical.   The total range is just too narrow (0.002").   The only reasonable way to adjust clearances is by shimming during final assembly.

Every time the cam carriers come off the engine,  the first step should be to check the valve clearances.   Then take the time to adjust the shims when the carrier goes back on.   In the case of a valve job,  all clearance settings will be lost during the process.

In that case, reassembly will require several trials.   First assemble the cam carriers to the head using thinner shims...  something on the order of .010" thinner than what was in there before.   Then measure the clearances that result to get a base line,  calculate what shims are required to bring the clearances into spec,  then R&R with the new shims.   Measure again and adjust again if necessary.

Regards,    Tim Engel