1882 Silveradao 454 with valve tick

N44252 · 05-28-2007, 09:08 PM

My 1982 Silverado 454 dually crew cab with only 25000 miles has suddenly developed a valve tick from the drivers side head. I intend to pull the valve cover and reset the "lash". The Chevy manual says to position the crankshaft on TDC at the compression stroke on the number 1 cylinder and then loosen the rocker arm nut, and then tighten it while spinning the push rod until the "lash" is gone. Does this mean until the pushrod no longer spins or what? I thought "lash" was any clearance between the rocker arm and the lifter. Also I thought the push rods were supposed to rotate while the engine is running as the valves do.
Assuming the problem is a lifter that is not pumping up is there any way to treat it short of replacing the lifter? I would appreciate any help with this. Thanks, N44252

75K30 · 05-28-2007, 11:17 PM

By turning the pushrod, you are determining zero lash, then once you have established zero, the nut should be tightened 1/8th to 1/4 turn. This sets the pintle depth inside of the lifter. You will have to go back and re-read the procedure for adjusting the valves. If you chose to adjust them with the engine off, you will want to learn more about the order, and where to rotate the engine. TDC is not necessarilly the right place to adjust the valve. It may not actually locate the lifter on the heel of the lobe. You will also have to make sure that the engine has temperature in it, or it will be wrong if adjusted cold, and the valve will never close all the way.
You will want to really disregard timing marks, and concern your self with valves on a given cylinder and their relationship to being fully, and complety open, yes open. For example, if you start by first verifying the number one cylinder intake valve is fully open, (when the rocker arm goes down all the way, without returning up again). This guarantees the #6 valves are ready for adjusting, and that they are on the base circle (heel) of the lobe, and are, or should be completely closed. Then you may make adjustments using the spin method, and finally tighten the nut down an extra 1/8 th turn. After one is done, you can move to the next one
Cylinder relationships are as follows:
1=6
2=3
4=7
8=5
Hope the relationship makes sense. Follow the relationship, and you can be sure that the valves will be set properly.
Always check the pushrod for straight, many times I have seen a lifter loose tolerance as a result of this. Some push in style studs start to pull out providing the same symptom. Inspection of the pivot points of the rocker is a good idea too. There is a reason that the valvetrain lost tolerance, hopefully it is not a cam lobe going flat.
Good luck.

N44252 · 05-30-2007, 11:43 AM

Thanks for the respose, I understand that the lifter must be on the heel on the camshaft lobe when making the adjustment. But, what I was asking is, do you spin the push rod with your fingers as you tighten down the lifter nut until it can no longer be spun with your fingers? Is that then "zero lash"? Also if a rocker arm stud has started to pull out what is the remedy, is there a remedy that does not involve pulling the head?

05-28-2007, 09:08 PM	#1
N44252 Junior Member Join Date: Apr 2007 Posts: 5	1882 Silveradao 454 with valve tick My 1982 Silverado 454 dually crew cab with only 25000 miles has suddenly developed a valve tick from the drivers side head. I intend to pull the valve cover and reset the "lash". The Chevy manual says to position the crankshaft on TDC at the compression stroke on the number 1 cylinder and then loosen the rocker arm nut, and then tighten it while spinning the push rod until the "lash" is gone. Does this mean until the pushrod no longer spins or what? I thought "lash" was any clearance between the rocker arm and the lifter. Also I thought the push rods were supposed to rotate while the engine is running as the valves do. Assuming the problem is a lifter that is not pumping up is there any way to treat it short of replacing the lifter? I would appreciate any help with this. Thanks, N44252

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05-28-2007, 11:17 PM	#2
75K30 Senior Member Join Date: Jul 2006 Posts: 2,636	By turning the pushrod, you are determining zero lash, then once you have established zero, the nut should be tightened 1/8th to 1/4 turn. This sets the pintle depth inside of the lifter. You will have to go back and re-read the procedure for adjusting the valves. If you chose to adjust them with the engine off, you will want to learn more about the order, and where to rotate the engine. TDC is not necessarilly the right place to adjust the valve. It may not actually locate the lifter on the heel of the lobe. You will also have to make sure that the engine has temperature in it, or it will be wrong if adjusted cold, and the valve will never close all the way. You will want to really disregard timing marks, and concern your self with valves on a given cylinder and their relationship to being fully, and complety open, yes open. For example, if you start by first verifying the number one cylinder intake valve is fully open, (when the rocker arm goes down all the way, without returning up again). This guarantees the #6 valves are ready for adjusting, and that they are on the base circle (heel) of the lobe, and are, or should be completely closed. Then you may make adjustments using the spin method, and finally tighten the nut down an extra 1/8 th turn. After one is done, you can move to the next one Cylinder relationships are as follows: 1=6 2=3 4=7 8=5 Hope the relationship makes sense. Follow the relationship, and you can be sure that the valves will be set properly. Always check the pushrod for straight, many times I have seen a lifter loose tolerance as a result of this. Some push in style studs start to pull out providing the same symptom. Inspection of the pivot points of the rocker is a good idea too. There is a reason that the valvetrain lost tolerance, hopefully it is not a cam lobe going flat. Good luck.

05-30-2007, 11:43 AM	#3
N44252 Junior Member Join Date: Apr 2007 Posts: 5	Thanks for the respose, I understand that the lifter must be on the heel on the camshaft lobe when making the adjustment. But, what I was asking is, do you spin the push rod with your fingers as you tighten down the lifter nut until it can no longer be spun with your fingers? Is that then "zero lash"? Also if a rocker arm stud has started to pull out what is the remedy, is there a remedy that does not involve pulling the head?