Valve lash.. Hot /cold ? How hot is hot?

Bewy said
I have only once measured the difference between hot/cold on an engine with iron block/alum heads. It was 0.003". Veeeeery easy to check. In my opinion, too much lash difference is allowed for alum heads. 0.003" for most alum heads, & 0.004" for a tall head [ that has longer valves/taller ports ]. Performance heads usually have s/steel valves; s/s expands at a higher rate, so that needs to be factored in, which means the hot to cold difference will be less.

To check on your engine. Have tools [ & feeler gauges, pen & paper ] ready for quick removal of the valve covers. Drive the car until engine is at normal operating temp. Switch off engine & quickly remove one v/cover. Check for loose rockers, measure the lash & record. Leave overnight to cool down & re-check the lash cold. There is your hot/cold difference.

I like the approach. I have silicone/rubber valve cover gaskets for easy removal. You indicate that the "difference" should be less. Are you of the camp that says that it will loosen up .003 as it heats up? Or that it will tighten as it heats up. For a .016 lash, would you cold set at .013?

I will set and measure all my valves and perform the test to heat them up and measure again. I will post all results.

For what it is worth, I set the original flash cold to cam card specs. Meaning that I was actually looser than I should have been. For those who follow/followed my degreeing cam thread, I now know that the cam events were retarded even more than the 8*retarded that the cam/crankshaft orientation said. By how much, I will have to do some studying. I will post if anyone is interested in how much .006 loose lash affects cam timing.