[Supras] valve bucket and shim rotation

[berniek at technicaldevelop.com]

Hi list.

    Just got done refitting the cam journal caps for my JDM rebuild.  The exhaust side of the head is assembled.  I ran it with a 1/2" drill and socket on the cam bolt for about 15 minutes, flooding the sides of each journal with oil.  Found a few valves with slightly excessive clearance, once everything normalized.  I added some .002" and .0025" shim stock between the existing shims and buckets to bring the clearance as close to .0095"-.010" as I could get it for the exhaust side.

    However, during the run-in I found that in many cases the shims and/or buckets were not rotating.  The shims have some swirl marks from previous rotation, as cam lobes are customarily ground with a very small amount of taper to cause lifter or shim rotation.  In this case, however, I found some barely visible in-line scuff marks on the shims indicating that they were not rotating.  

    Miking the cam lobes shows no side to side taper at all, despite the fact that the lobes (exhaust) are 1.507", well above the minimum of 1.496" stated in the TSRM.  I could turn the shims over, presenting a new wear surface for the lobes, but a dial indiator and surface plate show the shims to be flat within a quarter thousandth on either side.  

    I can put a small amount of taper into the cam lobes with the tool post grinder and fine grit wheel in the lathe, not more than a thousandth or so.

    Any comments about lobe taper, shim rotation, etc., would be appreciated.  Thanks.

            BernieK