what length pushrods did he use?
funny valvetrain noise
Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
funny valvetrain noise
My dad recently upgraded to Lingenfelter LS6 heads and their GT11 cam. It would make some loud tapping about 5 minutes into a drive and only last about 15 seconds and go away. Things ended badly when something failed while it was making a noise. The end of a rocker was broken off, an intake valve was bent, and a retainer mangled. Hard to say what broke first. To play it safe, he replaced the lifters, pushrods, and rockers with new stock parts. Now the car is back to tapping again and it is starting to last longer than 15 seconds and can now be minutes long.
The only things that are the same are the heads themselves, the cam, and the shop that did the work so we are wondering what it could be. What could be some possible causes?
The only things that are the same are the heads themselves, the cam, and the shop that did the work so we are wondering what it could be. What could be some possible causes?
Melting Slicks
Joined: Jul 2005
Posts: 2,586
Likes: 2
From: Bardstown Kentucky
If the heads were decked I would imagine pushrod length as well. If it had a bent valve I would assume you had the heads gone through. I would check the wipe pattern or get an adjustable pushrod and check the length.
Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
I would assume Lingenfelter would have the quality control not to use a decked core.
The heads supplied by Lingenfelter should not have been decked and weren't decked by the shop. The stock pushrod length was used, but I doubt the shop went through the trouble of verifying it. I called Lingenfelter and they said that was fine as long as the heads were not decked by the shop and the gasket is the stock thickness. That is why I don't think the shop double checked.
It was the Lingenfelter 480 hp package so the LS6 heads were ported and polished, port matched, and had a valve job.
If the pushrods are indeed the incorrect length, wouldn't there be a tapping all the time rather than some of the time?
The heads supplied by Lingenfelter should not have been decked and weren't decked by the shop. The stock pushrod length was used, but I doubt the shop went through the trouble of verifying it. I called Lingenfelter and they said that was fine as long as the heads were not decked by the shop and the gasket is the stock thickness. That is why I don't think the shop double checked.
It was the Lingenfelter 480 hp package so the LS6 heads were ported and polished, port matched, and had a valve job.
If the pushrods are indeed the incorrect length, wouldn't there be a tapping all the time rather than some of the time?
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Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
I thought of that as well, but that seems like it would tap consistently when cold and gradually go away as it heats up or be quiet cold and get louder as it heats. This noise seems to come and go.
Melting Slicks
Joined: Jul 2005
Posts: 2,586
Likes: 2
From: Bardstown Kentucky
When its there does it seem to be in one place or moving around? Again its hard to say without knowing some details, if the valve bent the valve seat could be messed up if there was no valve job done afterwards.
Safety Car
Joined: Sep 2003
Posts: 3,558
Likes: 2
From: Cape Coral FL
I vote for incorrect pushrod length. If you used non-decked heads and a stock thickness head gasket using a stock length pushrod would be correct. However an aftermarket cam with higher lift lobes requires a smaller base circle. That means the lifter will sit lower in the bore when traveling on the heel and consequently the lifter preload amount will decrease.
One other possibility would be oil aeration due to a pinched o-ring. If the oil pump was removed when the cam was pulled it's possible that the o-ring was either re-used or got pinched when it was re-installed. I'm not saying this is the cause, but it will cause your symptoms.
One other possibility would be oil aeration due to a pinched o-ring. If the oil pump was removed when the cam was pulled it's possible that the o-ring was either re-used or got pinched when it was re-installed. I'm not saying this is the cause, but it will cause your symptoms.
Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
He had the Lingenfelter package on for like 2000 miles and then it bent the valve. The head was removed, given a valve job and new valve, and reinstalled.
Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
He thinks it is from one stationary area and the valvetrain noise gets about 5x louder. It seems to be coming from the driver's side whereas the busted valve head was the passenger side.
Melting Slicks
Joined: Apr 2003
Posts: 2,150
Likes: 6
From: NS
Obviously valve to piston clearance issue. Is the cam timed correctly? Is it off a tooth? If he keeps driving it with the noise and damage you described he's risking destroying the engine if it drops the valve.
How about valve springs? Do you have correct seat and nose pressure per the cam specs?
How about valve springs? Do you have correct seat and nose pressure per the cam specs?
Last edited by Atok; Jul 26, 2009 at 08:07 AM.
Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
Obviously valve to piston clearance issue. Is the cam timed correctly? Is it off a tooth? If he keeps driving it with the noise and damage you described he's risking destroying the engine if it drops the valve.
How about valve springs? Do you have correct seat and nose pressure per the cam specs?
How about valve springs? Do you have correct seat and nose pressure per the cam specs?
The valve springs are the high lift kit from Lingenfelter that is required with the GT11 cam. Not sure about seat pressure and all.
Thread Starter
Racer
Joined: Jul 2004
Posts: 444
Likes: 0
From: Dallas TX
He says it sounds like this video except if he rev's it, it sounds like it misfires.
http://www.youtube.com/watch?v=FdBa44L_6b4
http://www.youtube.com/watch?v=FdBa44L_6b4
