valves not seating, cam install
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On The Tree
Joined: Mar 2006
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valves not seating, cam install I am swapping a 2002 z06 cam into my 5.3 turbo motor. I have just replaced the valve springs with gm yellow springs, and the pushrods with comp cams hardened 7.4".
I am reinstalling the rocker arms and have torqued them too 22 ft/lbs, than rolled the motor over 180* and rechecked torque values.
I am noticing that some of the valves are not, or rather do not seem to be, fully closing. For example, the #2 intake valve opens fine and closes fine where I can just barely wiggle the rocker. The #2 exhaust valve however is noticeably compressed when it should be closed and is never wiggly.
I have rolled the motor over multiple times and hear/feel no valves hitting pistons. right now the spark plugs are out of the motor
So, could some of the lifters be stuck? or still have oil in them? I am really confused here
any help would be great!
thanks, Matt
I am reinstalling the rocker arms and have torqued them too 22 ft/lbs, than rolled the motor over 180* and rechecked torque values.
I am noticing that some of the valves are not, or rather do not seem to be, fully closing. For example, the #2 intake valve opens fine and closes fine where I can just barely wiggle the rocker. The #2 exhaust valve however is noticeably compressed when it should be closed and is never wiggly.
I have rolled the motor over multiple times and hear/feel no valves hitting pistons. right now the spark plugs are out of the motor
So, could some of the lifters be stuck? or still have oil in them? I am really confused here
any help would be great!
thanks, Matt
Your exhaust valve lifter may not have bled down like the intake like you hinted at. What I would do to check the valve sealing is run a leak down test on the cylinder with it at TDC.
That is not the correct rocker procedure, not sure where you got it. Lifter will bleed down in a minute or so. Is this the only valve that looks like this? If not, what are the others?
Here is the correct GM procedure:
Here is the correct GM procedure:
Last edited by vettenuts; Oct 31, 2009 at 08:18 AM.
Are you sure both valves are on their base circles when you observe this anomoly? I don't believe 22ft/lbs is enough to bend a valve stem. Would you continue to turn the torque wrench if you started to feel a mechanical bind? I hope not.
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However, I did miss one key point in the OP's post. The rocker can't be wiggled so the valve spring is still putting a force on it. If the valve were bent, the rocker would be loose so the valve should be OK. I modified my post.
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The lifters should be on the cam base circle when the rockers are torqued. If your pushrod won't turn now, wait for ten minutes then check again. If it won't turn now, you either have a stuck lifter, or your pushrods are to long. Hope this helps, Dean. P.S. this is for hydraulic lifters only.
Vettenuts method will properly position the lifters on the base circle. However I would Not even install any of the rockers unless they Are on the base circle. Then Torque these rockers. I do not like to turn a engine over with ANY of the rocker bolts not torqued. Dean.
