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Valvetrain Chatter

brandonl2000

brandonl2000

New member
Before I start throwing money guessing at problems, I want as many opinions as I can get.

Car has done this since I've got it but I've left it on the back burner. Problem is when the engine hits 2200 rpm, there is an unhealthy chattering sound.

Current theories are bad lifter(s), dying spring, or a bad rocker(s) (shims and hinges). Car has no misfires or knock.

Please take a listen at the video, give me your thoughts. I don't mind replacing any of this but I hate to pull the top end off more than once if I don't have to.
Current set up is 90# springs and GT1 cam l36 block. I assume rockers, lifters and pushrods are all stock.


15 Seconds is when I really hit the sweet spot.
 


Someone, told Brandon to post up and get a lot more opinions.

My thought is.. either a lifter is going or he has that one 3800 that the lifters with that cam etc didn't soak up enough space. Hence it's noisy
 
Well I'm going with cheapest, most probable, and most accessible. Gonna swap new springs and rockers into it in the coming weeks. If that doesn't do it... then I can either tear it apart or just drive it into the ground. I have no preference, depends what mood I'm in. :D

Probably just replace the 90# with 90#. Just not sure how to find "new" stock rockers.
 




Lifter issue is a possibility, but I don't see how he would have pushrod length issues assuming he is on stock lifters.
 
There is a different cam in the engine. Anytime you change a cam, you should technically measure every pushrod length and order the appropriate length. In 3800's the lifters give and take so much that we typically bolt and go w/o a thought to measuring.
 
From what I've read the preload tolerance on stock lifters is enough to soak up the base circle difference. But the ls7 lifters have a tighter tolerance and that's when guys run into issues.
 
and ....how about if a lifter is bad? say it's partially clogged or something so it'll have enough oil at low rpm, but when it's moving fast it can't get enough in?
 


That is a possibility as I said. But every time I have ever personally encountered lifter issues, the noise happens at low rpms when cold, and will get better with higher rpms and the car getting warm.
 
PS.. you should have a mechanics stethescope and pull the VC, listen to all pieces by touching the head next to each rocker. You'll know quick if it's a spring/rocker.

That's exactly what I did when my L67 in the GS went. I had a ticking. Listened right at the exhaust manifold and VC etc, knew it was #5. Pulled VC and found nothing wrong with spring or rocker. No play in push rod. Knew something was up, without pulling the head, I wouldn't have found out anything though. I kept running it and poof.. #5 valve hung.
 
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