Valve lash?
Thread Starter
Racer
Joined: Aug 2000
Posts: 400
Likes: 0
From: Irmo, S.C
Valve lash?
This may be a stupid question, but I don't want to make any mistakes. I'm installing roller rocker's tonight, and I've never done it before. From the Chilton manual it looks rather simple, but I have a question on the valve lash. The manual describes how to adjust the lash out per valve, but I'm not perfectly clear on what lash is:) Can someone explain it?
Thanks,
Jason
Thanks,
Jason
Drifting
Joined: Mar 1999
Posts: 1,931
Likes: 1
From: Norcross GA
Re: Valve lash? (97Supra)
There are a couple different approaches. W/ Hyd lifters, basically you wanna remove all the play in the mechanics of the valve lift, w/o compresing the lifter too much. If you go psycho, the valve will stay open. This point will be obvious.
In a loose state the lifter will click. Tighten down the keeper nut until the clicking is gone, then tighten 1/4 -> 3/4 a turn. i.e. Remove the play, then tighten a little more.
In a loose state the lifter will click. Tighten down the keeper nut until the clicking is gone, then tighten 1/4 -> 3/4 a turn. i.e. Remove the play, then tighten a little more.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Valve lash? (97Supra)
A lifter has a spring loaded center plunger upon which rides the pushrod. Valve lash sets the preload on the valve lifters or how far this plunger is depressed within the lifter; the usual preload is about .030".
The reason for the preload is so that the plunger doesn't bottom out nor hit it's retainer clip on the top of the lifter bore during normal operation.
With zero preload, the plunger is at the top of it's bore. On an L98, the proper preload is set by tightening the rocker nut about 1/2 turn past zero lash. I do this by closing the valve and backing off the rocker nut to relieve all tension on the pushrod and then slowly tightening the nut till I just feel resistance, while twirling the pushord. At that point I tighten the nut 1/2 turn and lock it in position.
The reason for the preload is so that the plunger doesn't bottom out nor hit it's retainer clip on the top of the lifter bore during normal operation.
With zero preload, the plunger is at the top of it's bore. On an L98, the proper preload is set by tightening the rocker nut about 1/2 turn past zero lash. I do this by closing the valve and backing off the rocker nut to relieve all tension on the pushrod and then slowly tightening the nut till I just feel resistance, while twirling the pushord. At that point I tighten the nut 1/2 turn and lock it in position.
Le Mans Master
Joined: Nov 1999
Posts: 8,511
Likes: 3
From: Memphis, Tn
Re: Valve lash? (97Supra)
Lash is the clearance between the top of the valve stem and the tip of the rocker. With a mechanical cam, lash is determined with a feeler gauge inserted between the valve stem and the rocker. With a hydraulic cam, you adjust the rocker until all lash (clearance) is removed, then tighten the adjustment nut an additional 1/2 turn.
I just did mine 2 weeks ago. The manuals give a lot of directions about checking the lash when the piston is at top dead center on the compression stroke, or adjust the intake just as the exhaust starts to open, etc., etc., etc.
Here's what I did. Put the new rockers on, and adjust all of them to zero lash. Doesn't matter where the piston is. Turn the engine a little, no more than 1/4 turn of the crankshaft. Check all the rockers. A few will be loose. Adjust these to zero lash. You can quickly check the rockers by wiggling them. It will be obvious which ones became loose. Turn the crankshaft a little more, and re-check and re-adjust. Do this until the crankshaft has gone around 2 times. Now you're done. Go have a beer on a job well done. :cheers:
I just did mine 2 weeks ago. The manuals give a lot of directions about checking the lash when the piston is at top dead center on the compression stroke, or adjust the intake just as the exhaust starts to open, etc., etc., etc.
Here's what I did. Put the new rockers on, and adjust all of them to zero lash. Doesn't matter where the piston is. Turn the engine a little, no more than 1/4 turn of the crankshaft. Check all the rockers. A few will be loose. Adjust these to zero lash. You can quickly check the rockers by wiggling them. It will be obvious which ones became loose. Turn the crankshaft a little more, and re-check and re-adjust. Do this until the crankshaft has gone around 2 times. Now you're done. Go have a beer on a job well done. :cheers:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Valve lash? (85 Dave)
So 85 Dave, once you get them all to zero lash then you just crank each rocker each another 1/2-turn to set the preload??
Sounds like a plan. :cheers:
Sounds like a plan. :cheers:
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Le Mans Master
Joined: Nov 1999
Posts: 8,511
Likes: 3
From: Memphis, Tn
Re: Valve lash? (97Supra)
Hi. I think there are 2 yacht cove's. One is a condo complex on the lake off #6 and one is a downtown apt. complex. Are either of those it?
Jason
Jason
