what is the deal with my 225 /six compression?

Personally I prefer to adjust lash when engine is running, however with big overlapping cam, and higher than factory idle, engine is moving too much, oil squirts all over inner fender, firewall, floor, and windshield; one PIA. Until I added more mufflers I could not hear valve to rocker sounds during lash adjustment. So now I warm her up real good, shut her down, pull all plugs, valve cover, and adjust all of them in pairs; 1&6 etc. with three rotations of crank; it’s quick, much cleaner, and wrist & knuckles feel better after.

Factory Service Manual directs one to adjust while engine is fully warmed up, and running. The important point is to have engine up to operating temperature to take into account all the liner thermal expansion of its moving parts of valve train. Lashing a cold engine without adding this heat expansion into the adjustment can cause too tight lash setting once engine is up to temperature, and burnt valves from never fully closing.

Lash too tight is much more of a problem than too loose. Clattering won’t hurt anything within reason. You can hear the difference in sound on a quiet engine/exhaust; as lash is loosened going from sowing machine tic-tic-tic to tap-tap-tap to clat, clat, clat. Clat, clat is where things begin to get too loose.

As far as force exerted on rocker and valve stem, spring load is the same when contact is initially made a wee bit further along opening ramp, stem velocity is a bit higher and accelerates the further along the ramp contact with rocker is made. I haven’t read about any harm in running with 0.028” lash, some of the HP /6 engines run this kind of lash in excess of 6000 rpm., just make for a noisy valve train. If using a stock cam, one will get a sluggish engine at these big lash settings because valves are not fully opening, or staying open long enough for a complete A/F cylinder fill.

Once again loosening lash by increments of 0.002” to say 0.004”on a stock engine will make huge changes.