|
Walt / Bruce
When you say you've measured the valve clearance on a "hot engine" with a feeler gauge, don't forget that the "hot" portion of the valve head and stem inside the port (exposed to exhaust gasses) has already cooled down by several hundred degrees °C from its true operating temperature (and has therefore significantly decreased in its length), during the time it takes to stop engine, remove covers, measure lash.
Some rough calcs give about 0.35mm expansion/contraction for this "hot" part of the valve alone (L=40mm, 500°C, 17.3E-6mm/mm/°C for stainless)
I'd content that the actual operating valve clearance in a running engine, as opposed to a "hot" stationary engine actually decreases with increasing temperature.
Cam opening ramps are designed to to limit the impact speed of cam lobe on the rocker during takeup of the lash (clearance), allow for expansion of the hot valve, and allow for a small variation of the adjustment of lash.
So here's a confidence test for your assertion that the clearance expands, which I DO NOT RECOMMEND......set all of your lash clearances to zero on a cold engine (or hot stationary engine) and run it - I'm fairly certain that will burn every exhaust valve, and it will run like a POS all the way to destruction !!!
John
|