Setting Valve Lash - A Few Tips

[davepl]

I've seen this done incorrectly more and more recently, and I'm unsure why, but I thought I'd throw this out there.

When you go to set lash (hydraulic), don't do it running. I used to do it that way, with the little clips that only let 95% as much oil get in your eyes and on the headers. Ugly stuff. Google how to do it statically based on valve opening/closing periods.

Anyway, what people get wrong is finding zero lash. Is is NOT when start to feel drag trying to rotate the pushrod back and forth. By the time you feel binding there, you've got plunger down already.

Zero lash is when you move the pushrod up and down as you tighten the nut, and then -just- as there's no slack when you move it up and down.

Then set it from there (1/4 turn or 3/4 turn or whatever you neighbor across the back alley taught you).

If you do it based on the rotating the pushrod approach and then add a turn (or whatever) you'll run the risk of having so much preload that when oil pressure comes up the valves can hang open.

Not sure if that could cause piston-to-valve issues, but I imagine it could in some close engines. But in any case if a valve hangs open the car won't run right, and could backfire through the carb (intake hung open) or exhaust (exhaust hung open).

Others may have more and better input, just throwing this out there in case it saves someone a headache down the road.

Cheers!
Dave