[olddog]

Originally Posted by RET_COP

I'm not an engineer and without doing any in depth reading on valve lash, it seems to me that lash has everything to do with expansion of metals, allowing the valve to fully close, and that's it. Its there because the engine does not operate in a perfect setup, that is to say that in a perfect set up that would be no lash, just the lifter following the cam lobe, no slamming, no space to take up, no expanding metals, valve closing fully on the base circle, springs holding it all together. That would be absolutely perfect. The ramp designs have everything to do with acceleration/deceleration and how the lifter and springs coincide with each other, and stress on parts. The hydraulic would be perfect except there are more parts to it, it is heavy and it requires oil to hold the plunger up.
Lou

So then why do the cam specs tend be in the 0.020" inch gap range when hot? A cast iron engine is generally 0.005" tighter when cold give or take. They could still be 0.010" tighter before hitting zero lash cold, and they do not do this, even though they could.