Food for thought regarding lash... Less is not always more!!! Running the lash significantly tighter than the recommended setting can cause problems. First, metal expands when heated and parts like valves tend to "grow" when the get hot, especially at full throttle. I have always preferred to set mechanical valve trains "hot". That is, with the engine up to operating temperature, for a more accurate setting. This is while "cold" settings tend to be looser by a couple thousandths. Even so, the lash will tighten when the engine is running. Second, the valve train must go slack, or unload each cycle. This is important for oiling and cooling. The lifter pressure must release to allow a fresh film of oil between the lifter face and cam lobe. The lower anti-scuff additive (zddp) levels in current oils make them less forgiving of hard metal-to-metal contact, so it's best to ensure the oil film is maintained. Also, while the valve stem has a big spring to act as a radiator, the valve head relies on seat contact for cooling. That 400 degree exhaust valve doesn't have a lot of time to dump heat into the 200 degree head at high RPM, so positive contact is crucial.
In a worse case scenario, too tight lash will cause the valve train to "go solid" and prevent the valve from closing all the way. While the compression loss will cost some power, the big worry is valve overheating. The valve gets hot, expands, and loses seat contact causing the valve to get hotter, expand more, and lose more seat contact. Hot exhaust gasses passing by on the seat will cause this to snowball. If the valve gets too hot it may overheat and be damaged by warping. If the stem overheats and sticks in the guide, piston contact will really warp (bend) the valve causing permanent damage.
Some will claim that lash can be used as a "tuning" tool. Sure, increasing or decreasing the lash will reduce or increase effective duration, if only slightly. It's no way to make one cam act like another. The bigger picture is to make sure there is adequate lash to prevent valve float at high RPM. The cam grinder will give a conservative lash recommendation to prevent this. Can you run tighter lash? Depending on spring pressure, valve train weight and flex, RPM and other things, probably. That's what "test and tune" runs are for.
Noise is a fact of life with mechanical cams. Aluminum valve covers will block it some, but don't risk the health of the engine to make it "quiet". Any hot rodder who knows anything will respect the even ticking of a well adjusted mechanical. And we all know chicks dig a nice solid stick, so don't pass on a chance to show off old school.
