FishFry wrote: ↑Sun Dec 04, 2022 7:15 am
Let me rephrase my question.
Given that on a 261 with solid lifters the lash gets wider when hot, I was questioning my self - why would you want anything more than zero lash (when cold)?
From what I know, hydraulic lifters always try to keep it zero lash, when the engine is running. So zero lash (or as close as possible) is a good thing - right?
With solid lifters we can't have that - the next best thing would be to set the lash to zero (cold) and live with whatever gap they end up when hot.
Did I miss something? Would there be any adverse effects?
Why is there a spec for anything more than zero (when cold) anyway, when the gap widens at operation temperature?
Why would I want a gap in the first place - what is it for?
Frank
Every mechanical cam profile(Flat Tappet, or Roller is designed for a give Hot lash. Above the point, is the lift curve the cam designer wants, to open and close the valve. Below that point, is the lash ramp that the cam designer designed to take the lash out on the opening side, and to gently seat the valve on the closing side.
The lash ramp is much slower then the lift curve above it.
If you set your hot lash tighter then what the cam designer designed it for, you will be opening and closing the valve in the middle of the much slower lash ramp. This will increase duration, without adding almost any area. This will turn a good cam design into a lazy cam design. This is why you need to set the Hot valve lash to where it's designed to be set.