Hyd. valve setting -I/2 or 1 turn ????
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Racer
Joined: Oct 2003
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From: Plains Ga.
Hyd. valve setting -I/2 or 1 turn ????
When setting the valves on a LT1, once you have gotten the up & down movement of the pushrod removed, what is the reccommended
amount of turn on the rocker arm nut---1/2 or 1 turn????
Will 1/2 turn result in less valve lift than a full 1 turn???
Just a thouhgt,
JTHVETTE
amount of turn on the rocker arm nut---1/2 or 1 turn????
Will 1/2 turn result in less valve lift than a full 1 turn???
Just a thouhgt,
JTHVETTE
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The service manual for my 92 LT1 says one turn after zero lash. The manual defines zero lash where you use your fingers to rotate the pushrods and tighten the rocker nut until you can no longer rotate it. Then tighten one additional turn.
With #1 piston at TDC, adjust the exhaust valves for cylinders 1,3,4,8 and intake valves for cylinders 1, 2, 5,7. Rotate the crank one full turn so that the # 6 cyinder is at TDC and adjust exhaust valves 2,5,6,7 and intake valves 3, 4, 6, and 8.
Because the ECM limits RPM through a fuel cutoff at around 5850RPM, you should not be able to increase the rev limit through valve lash. Hydrulic lifters do take up some slack in the valve train. If you tighten the rocker arm nut too tight, the valve may open more but there could be a risk of piston-to-valve contact which is not a good thing....
With #1 piston at TDC, adjust the exhaust valves for cylinders 1,3,4,8 and intake valves for cylinders 1, 2, 5,7. Rotate the crank one full turn so that the # 6 cyinder is at TDC and adjust exhaust valves 2,5,6,7 and intake valves 3, 4, 6, and 8.
Because the ECM limits RPM through a fuel cutoff at around 5850RPM, you should not be able to increase the rev limit through valve lash. Hydrulic lifters do take up some slack in the valve train. If you tighten the rocker arm nut too tight, the valve may open more but there could be a risk of piston-to-valve contact which is not a good thing....
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by c4cruiser
The service manual for my 92 LT1 says one turn after zero lash. The manual defines zero lash where you use your fingers to rotate the pushrods and tighten the rocker nut until you can no longer rotate it. Then tighten one additional turn.
Originally Posted by c4cruiser
With #1 piston at TDC, adjust the exhaust valves for cylinders 1,3,4,8 and intake valves for cylinders 1, 2, 5,7. Rotate the crank one full turn so that the # 6 cyinder is at TDC and adjust exhaust valves 2,5,6,7 and intake valves 3, 4, 6, and 8.
Originally Posted by c4cruiser
Hydrulic lifters do take up some slack in the valve train.
Originally Posted by c4cruiser
If you tighten the rocker arm nut too tight, the valve may open more but there could be a risk of piston-to-valve contact which is not a good thing....
I hope this helps to dispel some false concepts.
RACE ON!!!
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
The object of the 1/2-1 turn is to properly preload the lifter plunger, i.e. center it (roughly) within it's bore within the lifter. There is a range to this poition so we have the 1/2-1 turn.
Unless the preload is too close to the lifter bottom or top (assuming the valve springs are doing their job as is the lifter) you will gain nothing more from "tweaking" this adjustment.
I've found that, when twirling the pushrod, I can detect "zero lash" to within 1/8 turn so I set preload to 1/2 + 1/8 turn after I detect zero lash assuring that the preload is set to 1/2-3/4 turn.
Unless the preload is too close to the lifter bottom or top (assuming the valve springs are doing their job as is the lifter) you will gain nothing more from "tweaking" this adjustment.
I've found that, when twirling the pushrod, I can detect "zero lash" to within 1/8 turn so I set preload to 1/2 + 1/8 turn after I detect zero lash assuring that the preload is set to 1/2-3/4 turn.
