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Posted by David on Sunday, June 28, 2009 at 15:56:14 :
In Reply to: Pulled the heads on the PW today posted by Tim Holloway on Saturday, June 27, 2009 at 16:46:53 :
Make sure after your valve job that all the valve stems are the same length. This meaning when the valve is in the seat that the stems all stick out the same distance from the head. Put a straight edge across the tops of the stems to check. A good shop should do this and trim the stems to all the same distance. This will ensure all your lifters have the same preload and reduce wear on the cam shaft.
Some engines the preload on the lifters can be adjusted with shims under the rocker arm retainer. I am not sure about your engine but some engine designs only one bolt holds down a bridge which secures both the intake and exhaust rocker arms. You need the stems the same length if you want the preload to be equal.
I had the worst running engine in a jeep once and found the exhaust lobes on the cam were flat due to a poorly done valve job, too much preload wore them down.