Hydraulic Roller Valve Lash?
Melting Slicks
Joined: Nov 2000
Posts: 3,388
Likes: 1
From: X
Re: Hydraulic Roller Valve Lash? (Langadorf)
HYDRAULIC lifters:
1.Back-off or tighten the rocker arm adjusting nut so the rocker arm is loose
2.While rotating the valve push-rod between your fingers, SLOWLY tighten the adjusting nut until you feel a SLIGHT
increase in the effort required to spin the push-rod. Wobble the rocker-arm just to be sure it’s not cocked slightly
3.At this point you have zero lash in the valve train.
If you’re looking for higher rpm before valve float caused by lifter "pump-up", tighten the rocker adjusting nut an
additional 1/8th to 1/4 of a turn.
If you’re not going racing, tighten the adjuster nut one (1) turn from the "zero lash" point. (One turn is what is used on
virtually all Chevrolet engines).
[Modified by JonM, 2:59 PM 9/28/2002]
1.Back-off or tighten the rocker arm adjusting nut so the rocker arm is loose
2.While rotating the valve push-rod between your fingers, SLOWLY tighten the adjusting nut until you feel a SLIGHT
increase in the effort required to spin the push-rod. Wobble the rocker-arm just to be sure it’s not cocked slightly
3.At this point you have zero lash in the valve train.
If you’re looking for higher rpm before valve float caused by lifter "pump-up", tighten the rocker adjusting nut an
additional 1/8th to 1/4 of a turn.
If you’re not going racing, tighten the adjuster nut one (1) turn from the "zero lash" point. (One turn is what is used on
virtually all Chevrolet engines).
[Modified by JonM, 2:59 PM 9/28/2002]
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Hydraulic Roller Valve Lash? (JonM)
HYDRAULIC lifters:
1.Back-off or tighten the rocker arm adjusting nut so the rocker arm is loose
2.While rotating the valve push-rod between your fingers, SLOWLY tighten the adjusting nut until you feel a SLIGHT
increase in the effort required to spin the push-rod. Wobble the rocker-arm just to be sure it’s not cocked slightly
3.At this point you have zero lash in the valve train.
If you’re looking for higher rpm before valve float caused by lifter "pump-up", tighten the rocker adjusting nut an
additional 1/8th to 1/4 of a turn.
If you’re not going racing, tighten the adjuster nut one (1) turn from the "zero lash" point. (One turn is what is used on
virtually all Chevrolet engines).
[Modified by JonM, 2:59 PM 9/28/2002]
1.Back-off or tighten the rocker arm adjusting nut so the rocker arm is loose
2.While rotating the valve push-rod between your fingers, SLOWLY tighten the adjusting nut until you feel a SLIGHT
increase in the effort required to spin the push-rod. Wobble the rocker-arm just to be sure it’s not cocked slightly
3.At this point you have zero lash in the valve train.
If you’re looking for higher rpm before valve float caused by lifter "pump-up", tighten the rocker adjusting nut an
additional 1/8th to 1/4 of a turn.
If you’re not going racing, tighten the adjuster nut one (1) turn from the "zero lash" point. (One turn is what is used on
virtually all Chevrolet engines).
[Modified by JonM, 2:59 PM 9/28/2002]
This where lots of guys get tripped up. You're only feeling for SLIGHT resistence when turning the pushrod.
An alternate method, which I use and recommend to prevent missing the "SLIGHT' setting, is to use the up and down method on the pushrod. As you slowly tighten the adjusting nut/poly-lock, once the pushrod can no longer be moved up or down, you've also found "zero lash".
The other critical factor is making absolutely sure the lifter is on the base circle of the camshaft lobe BEFORE you being your tightening of the nut/lock. If the lifter is NOT on the base circle, but on the lobe's ramp instead, your adjustments will be off.
In degreeing a camshaft the most critical part is finding absolute Top Dead Center of the #1 piston while on the compression stroke; in setting lifter preload it's finding the point that the lifter is on the base circle of the lobe.
You'll know it when the engine idles like SH** or not at all when you fire it up.
I've got a step by step I can send you if you need it. Let me know.
Hope this helps.
Jake
[Modified by JAKE, 4:11 PM 9/28/2002]
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
Re: Hydraulic Roller Valve Lash? (JonM)
JonM...
I agree with this on virtually all GM engines EXCEPT for the L98. If you do this on an L98 with stock valve springs, it will run like dog poopie. It will not idle worth a flip, and it will loose power at all RPM's.
The reason for this is GM used extremely light valve springs on the L98 to reduce friction/reciprocating power losses, after all, it is a low rpm designed engine made for torque response and fuel economy. The extra tightening will cause the lifter to pump up that extra little bit and open the valve even on the base of the cam. Stock L98 springs really are that weak!
Then again, if you are touching an L98 valvetrain, you need to put in better springs in the first place. Pioneer 'Z' springs come to mind as the most cost effective fix...and they have good tension for RPM's as well.
[Modified by BBA, 5:21 PM 9/28/2002]
[Modified by BBA, 5:22 PM 9/28/2002]
If you’re not going racing, tighten the adjuster nut one (1) turn from the "zero lash" point. (One turn is what is used on
virtually all Chevrolet engines).
virtually all Chevrolet engines).
The reason for this is GM used extremely light valve springs on the L98 to reduce friction/reciprocating power losses, after all, it is a low rpm designed engine made for torque response and fuel economy. The extra tightening will cause the lifter to pump up that extra little bit and open the valve even on the base of the cam. Stock L98 springs really are that weak!
Then again, if you are touching an L98 valvetrain, you need to put in better springs in the first place. Pioneer 'Z' springs come to mind as the most cost effective fix...and they have good tension for RPM's as well.
[Modified by BBA, 5:21 PM 9/28/2002]
[Modified by BBA, 5:22 PM 9/28/2002]
