So after the drive to CA from NM, my engine has slowly developed this knock. When the motor was first started up, it had really loud valvetrain noise. Sounded like a sewing machine. But I read up on it and apparently that is common when running a big cam in an LS engine. So I thought nothing of it. Now when I arrived to CA, the car was running fantastic but the valvetrain noise seemed to be getting louder. And then the sound changed a bit from sewing machine to a steady knocking consistent with RPMs. I immediately thought "pushrods" because I am running a 7.325 length pushrod to accomodate for the LS7 lifters being taller, and my milled heads being shorter. So I grabbed a set of stock length rods off a guy on tech for free, installed them and nothing changed. I have triple checked all the rocker arms for damage and torqued them down to 22 ftlbs. I don't *think* that this is a rod knock and I am starting to lean towards collapsed lifters. Since I had so much bad luck with the TSP LS7 lifters from the getgo that is my next thing to try but ffffuuuuuuuu I dont wanna pull the heads!!! Have a listen and tell me what you think..... Oh BTW everything in the motor has about 1000 miles on it.

Oh and another question. In the last part of the video what I am doing is pulling the PCV valve out of the valve cover grommet, and there is a vacuum coming from the crankcase. As in the crankcase is sucking air IN instead of the vacuum line connected to the valve cover sucking air OUT of the crankcase. WTF IS THAT???? Anyone experience that before?? If I stick my finger in the grommet it will literally suck my finger into the valve cover, that's how strong of a vacuum this is. I'm baffled.
EDIT: I figured out the vacuum problem.
http://www.youtube.com/watch?v=8hmRGDSoEA4

 

If yours is the car I am thinking of, your passenger side header looked like it was sitting ON the crossmember. I didnt really feel like getting my finger burnt to check if there was physical contact or not but it sure looked like it. I'd fix that first, see what happens from there.

 

This knock is consistent with RPM's. Couldn't be a header hitting the K-member. But yes that is my car.

 

My checks would have been what you've done already--other than checking exhaust connections for leaks.

I guess pull the valve covers & watch the rockers as someone turns the key or turn it over with a breakerbar.

( Sounds healthy other than the tick! )

 

that happened to my bro-in-law, he kept thinking it was valvetrain related and it turned out to be a bad exhaust gasket. i cant hear too good but it sounds like it could also be a loose flywheel.

 

It runs perfect man. No smoking, no missing, nothing unusual at all!! The only other thing I can think of would be a clearance issue with the crank? But it wasnt making this noise when I first started it so maybe not. Ugh this is bothering me.

 

sounds like a header leak to me..i had that issue with mine also a loud *** knock even when i punched the gas..the last 2 bolts on my headers were loose..*lock tight them bastards LOL!!

 

At first I was going to say it was normal sewing machine noise as a result of your cam but it sounds a bit too loud to be just that.

BTW, Mine has a tick also(sewing machine sound), not as loud but I've had two respectable LSX shops check it(pushrods and length, torque specs, etc) only to tell me its normal.

Have you bounced off the rev limiter, maybe a bent valve?

 

Get a stethoscope and move it around to engine to narrow down where the noise is coming from.
A small header/head leak can sound a lot like a valve tick.
And some exhaust systems, my truck is one, can make it sound like something is amiss when its just the exhaust/exhaust tubing not quite in sync.

 

Check the injectors. I have ls1 injectors on my car & they are kinda loud. They do sound like a noisy valve train