Valve lash

crooked1/2dozen said
Hi y'all:

I had a deja vu last week when I set my rocker lash. Back about 1969-1970, Mr Rouse's auto shop class, there was a slant on a test bed, I had to set the valves on it after they were placed out of adjustment. Holding the 7/16th(?) wrench on a moving rocker....I knew I'd done it before!
But here's a question, I set my Triumph Bonneville lash when cold, .003Int and .005 Ex, lash is taken up as pushrods expand. Why do we set lash when warm, and why so much lash? I remember reading a thread somewhere and the person said if the lash is too small, compression will get too high, this doesn't seem to make sense to me. It would seem to me that if there were only a couple of thou lash when hot, no valves would be held open and wouldn't get burnt, plus with a trace higher lift, breathing would be better. But what do I know!

Someone 'splain this to me!

TIA

Dan

Lash to small compression to high? - nonsense - the opposite might be true - please note might if you a running very high cr and even then it does not make sense as a statement - increasing the lash will decrease your overlap and effective lift - increasing torque BTW - due to an increase in pressure - gas have have less time to escape while piston is moving up and valves are being closed

On a slant you get your most accurate setting setting them hot while idling
I have tried it repeatedly on different slants - and there is no cut an dried cold setting that works

I have a suspicion it has to do with the rockers being oiled under pressure
the oil acting as a hydraulic bearing and thus taking up clearance while under pressure - I know that 273 rockers had to be set this way as well for the best results