Inliners International Forums General Discussion Engines Valve Lash

Gentlemen,
I realize this question is ENGiNE 101, but....
I am not clear on how you check valve lash when adjusting solid tappet lifters on a 250 Chevy inline. Is lash the ability to spin the push rod between your thumb and finger? Or is it the up and down play between the rocker arm tip and the pushrod?
Ken

Lash is up and down clearance between the pushrod tip and rocker arm!

CNC Dude,
How do I gauge that?
Ken

Solid lift flat tappet cams have a lash value of some amount,similar to point gaps. Make sure the lobe on the cam of the valve you are checking is on its heel(the part that is opposite of full lift). You should have a cam spec sheet provided with the cam to tell the desired valve lash. Gently tighten the rocker nut until a feeler gage of the desired thickness can be inserted between the tip of the valve and rocker arm with light resistance. If you have a hydraulic flat tappet camshaft, it uses a similar procedure,except you eliminate all lash or clearance between the rocker tip and valve tip, and then tighten the rocker nut an additional 1/8-1/4 turn, typically!

Valve lash on a solid cam (depending on lift Or company made) can range from .015 to .035. My 583/607 lift crane cam had a .022 hot or cold. So check your cam card to see what it calls for Then you can adjust it from there Up Or down The wider the gap the Higher the rpm.smaller the gap Lowwer the Rpm.Kinda like
the effects of changing your timming.

Gentlemen,
The cam card reads "lash, hydraulic, hot" .
What technique(s) would you suggest for setting the lash?
Eager to learn more.
Thanks.
Ken

Use the second portion of my last post regarding hydraulic flat tappet adjustment! Make sure the cam lobe is on its heel portion for the valve you are adjusting. Rotate the pushrod between your fingers as you tighten the adjusting nut, and just as you feel the rocker arm start to apply tension against the pushrod, tighten it an additional 1/8-1/4 turn,typically! Some people prefer them tighter, you might need to tweak several after you start the engine and break the cam in to quieten them down. But that will get you close.

CNC,
If I understand correctly, I go to TDC for each cylinder, I want to just feel slight resistance while I am trying to spin the push rod, then go another 1/8-1/4 turn.
What I was doing before was going to TDC on each cylinder, tightening the nut until I was at the point where I was barely able to spin to spin the push rod, then going another 1/2 turn.
Thank you.
Ken

Ken, TDC isn't necessarily the point at which the cam lobe is on its heel. You will have to rotate the engine for each valve you are adjusting to make sure it is in the proper spot on the lobe. Just watch the motion of the pushrod rise and fall as you turn the engine slowly(either by hand or starter).Once you see that it has reached the bottom of its travel completely, then rotate just a little more to make sure its(lifter) fully seated in the lifter bore. And then adjust as you mentioned by spinning pushrod and tightening a half turn.

Somewhere in this thread it seems you have come to the final conclusion that you bought a hydraulic cam and hydraulic lifters.
It makes a difference. A big difference.

99.9% of the people try to spin the push rod to find zero lash screw it up. Even if you try to pre-oil the lifters, the spring inside the lifter is so soft, it is extremely difficult to feel the difference between zero lash and a half a turn or more below. The most common result of spinning the rod method is bent push rods.
DON'T USE THIS METHOD.
Just hold the end of the rocker with your fingers and slap it against the valve stem while you tighten the rocker nut. When the clearance goes away, you have "zero lash".
Most service manuals that tell you how to adjust hydraulic lifters on a I6, say to set cyl #1 at TDC and adjust specific valves. Turn the crank one turn(360 deg) and adjust the rest. For stock cams or near stock, that works just fine. A bigger cam means you need to start at TDC for #1. Turn the crank 120 deg for each cyl and follow the timing order.

Richard,
Yes, I have a flat tappet hydraulic cam. I opted to follow Leo Santucci's 120 degree increments adjustment as suggested in his book. Until your post I was still not clear on the "lash" determination. I may be a bit dimmer than you average member, however I wanted a clear method of lash adjustment. Your explanation has made it clear to me. Thank you.
Ken