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Valve spring changing procedure recommendations?

 
Old 11-24-2011, 08:46 PM
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Default Valve spring changing procedure recommendations?

I am in the process of replacing stock valve springs with new stock valve springs in a 2002 Z06. It is completely stock with 55k miles and I have no performance problems whatsoever. I have done some LT1s before but this is my first LS. A few questions:

1) I want to use the TDC method to prevent the valves from falling into the cylinder when I release the lock. Using the rockers and the crank position, how do I determine TDC for each cylinder?

2) What is the best method for adjusting the preload without the engine running and what is the spec for turns past zero lash?

3) What is the torque spec for the rocker arms?

I plan on using stock GM valve springs, inspect the seats/retainers/locks, replace the valve seals with stock GM and replace the valve cover gaskets with Felpro.

4) Any additional recomendations or deviations form this? Am I missing any critical steps in the procedure?

5) I have searched for a complete procedure/post using these methods, but I was unable to find one. Are there any good posts?

6) Is it worth gaging the install height and shimming to get them all exactly the same preload (I think the shims go down to 0.008 in)?
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Old 11-24-2011, 09:42 PM
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Answers are in red withing your quote below:

Originally Posted by pelensky View Post
I am in the process of replacing stock valve springs with new stock valve springs in a 2002 Z06. It is completely stock with 55k miles and I have no performance problems whatsoever. I have done some LT1s before but this is my first LS. A few questions:

1) I want to use the TDC method to prevent the valves from falling into the cylinder when I release the lock. Using the rockers and the crank position, how do I determine TDC for each cylinder?

Use a straw or wooden dowel down the spark plug hole while you have someone turn over the engine by hand. When the dowel stops moving up, you're at TDC.

2) What is the best method for adjusting the preload without the engine running and what is the spec for turns past zero lash?

There is no lash adjustment on LSx engines. The rocker arms are torqued to 22 ft-lbs, and the pushrod length is what determines the correct lifter pre-load. If you don't change anything in the valve train that would require different length pushrods, then you have nothing to worry about.


3) What is the torque spec for the rocker arms?

22 ft-lbs. Torque rocker arms when the valve springs are not under pressure. Do a search for "rocker arm torque" on this website and you'll find a page out of the Service Manual that shows the correct torquing procedure.

I plan on using stock GM valve springs, inspect the seats/retainers/locks, replace the valve seals with stock GM and replace the valve cover gaskets with Felpro.

4) Any additional recomendations or deviations form this? Am I missing any critical steps in the procedure?

Get the valve cover bolt grommets from Fel-Pro also. They are cheap.

5) I have searched for a complete procedure/post using these methods, but I was unable to find one. Are there any good posts?

Search the whole internet via Google ... I know there are some good write-up on other chat boards.


6) Is it worth gaging the install height and shimming to get them all exactly the same preload (I think the shims go down to 0.008 in)?

No ... you won't have to if you are just replacing the valve springs and valve guide seals. You will see that the GM valve guide seals have a built in valve seat in them. The installed spring height spec is 1.800 +/- 0.025" I believe from GM ... and if your heads are stock then you'll be within that. Only if you had valve work or head work done would I even worry about it.
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Old 08-17-2012, 08:55 PM
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i am also doing this. i have the cylinders full of air to remove the springs. is it normal to have air seeping past the valves?
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Old 08-19-2012, 05:19 PM
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Will be doing this soon, anybody
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Old 08-19-2012, 06:49 PM
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Originally Posted by ls1 ta View Post
i am also doing this. i have the cylinders full of air to remove the springs. is it normal to have air seeping past the valves?
If you have a pressure leak caused by the valve not properly seating then the valve is said to be non-concentric with the head.

If air is leaking out the exhaust then it is an exhaust valve. Crankcase would show poor ring seal or blow-by, and intake is intake valve of course.

Leaking air is not ideal as the efficiency of a combustion engine is determined by its ability to perform all 4 cycles of a combustion process. If you are getting blow-by or have a valve that is not concentric to the valve seat then you're losing HP as it shows realistically the wear or age on the motor.
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Old 08-19-2012, 06:56 PM
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take the heads off to do it, spend a tiny bit more cash and take them off.... its funner anyway..
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Old 08-19-2012, 07:10 PM
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if air is leaking past the valve you mite have to take the heads off .do a valve seat leak test with fluid.point the port up and fill with fluid and mark it.if the fluid level drops you mite need a valve job.
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Old 08-19-2012, 08:05 PM
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the cylinders will not seal completely... you will hear air hissing past something... usually the rings or the valves....
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