Inliners International Forums Thread Like Summary - Zero valve lash for solid lifters?

I'm thinking about valve lash settings a lot in the last time.
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

How is a lash softening this? If anything it creates an impact on the valve at opening, at closing it does nothing (at best) or even landing the valve harder, cause there is no rocker contact anymore, while the lifter is still riding on the soft ramp.

I don't get it. When I have a ramp already built into my cam, then what is the gap for (other than crating a sharp impact on my valve train at every valve event)?

Wouldn't that soft ramp work best with zero lash, so the lifter and everything else up to the valve would work like one solid piece and could closely follow that ramp, instead of the valve just sitting there and waiting to get a smack over the head with the rocker?

Frank

Long story shortened - the "clearance ramp" sections of a solid lifter grind were never intended to be used for lift - that's why the cam grinders card includes design specific lash specs. These specs are a compromise between duration, durability and chatter. As for the effects of thermal expansion - there are a whole lot of variables between cold winter ambient, summer day ambient and operating temperature. At initial startup the exhaust valves are the first component to heat up. If lashed too tight they cannot shed heat via the seats. Absent seat contact the heat will transfer up the stem - lengthening the valve in even further off the seat. The result will be burnt valves. The responses to your thread on HAMB include many other reasons to not experiment with zero lash on an iron block iron head engine.