Discussion and questions related to the course How to Degree a Cam
Does valve clearance values decrease or increase as engine goes from cold to hot.
Engine goes hot,valve clearances decrease.
That's the reason you apply valve clearance with the engine cold.
You want to reassure that with the engine hot the valve will stay closed when the camshaft is in its base circle.
Cool, thanks for reply.
Depends, I know some alloy head engines, that have hot and cold clearances specified, have greater hot clearances.
As with most of us, I assume you dislike setting them on a hot engine due to vurns, etc? What I have done in the past is to set them hot, if specified hot, them checked them cold and then used that to check/set the clearances - you need to have a relatively stable 'cold' temperature, though - if you live somewhere with summer temperatures pushing +40C and winter temps below zero, that is a fair range to cater for.
Some engines are supposed to be set hot and running - IMO, the only real difference between the running engine and hot but stopped, is the feeler gauges get chewed up almost instantly, it is much more difficult to 'feel' the resistance and you get burned from the hot, splashed oil.
You can make bumping the engine MUCH easier with something like this tool - https://www.ipdusa.com/uploads/images_products_slideshow/fullsize_6493.jpg which is connected to the starter solinoid and uses a momentary contact switch. Any auto' parts store should have several options.