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05 cts-V
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Discussion Starter #1
I had the valve covers off a few days ago and noticed something strange. I can get a .007 feeler gauge between the rocker and valve when ther is no load on the valve. The rockers also have a tiny bit of side play when there is no load on the valve.
Now I'm an old mustang guy that ran stud mount rockers with girdles and there was no play between the vavle and rocker. You tighten the rocker down till there is 0 lash and give it a 1/4 turn to preload the lifter.
I know the ls6 has a pedistill system but it should be adjusted with shims to get the right preload? Or is this the way that GM assembles there engines down the mass prouduction line.
Also, what do the stock springs look like. My springs seem to be a "beehive" type spring with yellow paint stripe. Is this stock?
 

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2005 CTS-V
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8,363 Posts
I had the valve covers off a few days ago and noticed something strange. I can get a .007 feeler gauge between the rocker and valve when ther is no load on the valve. The rockers also have a tiny bit of side play when there is no load on the valve.
Now I'm an old mustang guy that ran stud mount rockers with girdles and there was no play between the vavle and rocker. You tighten the rocker down till there is 0 lash and give it a 1/4 turn to preload the lifter.
I know the ls6 has a pedistill system but it should be adjusted with shims to get the right preload? Or is this the way that GM assembles there engines down the mass prouduction line.
Also, what do the stock springs look like. My springs seem to be a "beehive" type spring with yellow paint stripe. Is this stock?
Those are the stock valve springs. The Service Manual indicates that:
"Valve lash is net build, no valve adjustment is necessary."
I too would have expected some pre-load, but I have not done valve train work in a while. There is a procedure in the Service Manual for setting the torque levels on the rockers. It involves tightening the rockers when each of them is off the cam lobe.
 

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Discussion Starter #3
Thanks for the reply. I think the procedure that GM is talking about is the rocker arm being torqued down to the head at a certin value assuming that the valvetrain geometry, and lash has been checked.
I would think that in a performance application at high rpm's any lash in a hydrolic system would "shock" the lifter as the cam ramps up towrds the lifter making valve float unavoidable.
 

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2005 CTS-V
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Thanks for the reply. I think the procedure that GM is talking about is the rocker arm being torqued down to the head at a certin value assuming that the valvetrain geometry, and lash has been checked.
I would think that in a performance application at high rpm's any lash in a hydrolic system would "shock" the lifter as the cam ramps up towrds the lifter making valve float unavoidable.
I don't disagree with anything you have said. However, I do know that in a performance application (non-oem parts such as cam) the pushrod length has to be redetermined for the these motors. Additionally, the last time I was involved in setting valves on American V8s we set valve lash on solid lifters with the motor cold and set the pre-load (not unlike you described) on hydraulic lifters with the motor hot (or at least warm). Perhaps the valve lash you observe is only present when the motor is cold.

Finally, I have googled some articles on setting valve lash on LSX motors and they consistently say that no valve adjustment is necessary. Here is one article on aftermarket rockers in which the shimming process is determined for one set of rockers and then applied to all. (not the process for OEM which has but one rocker base.)

http://www.ls1howto.com/index.php?article=21
 

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Buy a set of adjustables. Its much easier than shimming. Personally have had great luck and a quite valve train with Crane gold rollers. I started with 1.7's and then moved to the 1.8's with the maggie. No problems with either.
 
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