Hi,

I was hoping to get some help finding the source of some engine knock...

I have an Internally stock LT1, supposedly has 70-80k on it. I put the motor in about 2k miles ago, and after replacing some burnt up spark plug wire (my bad), the motor is running pretty well.

I have a knock/noise that seems to be coming from the driver's side.

I have hooker long tube headers as well. I don't think they are leaking anywhere, no black streaks, and I can't feel or smell it anywhere.

All emissions/AIR systems are intact, new o2 sensors, new plugs, new wires.

The motor is throwing code DTC 32 EGR, but I have not really investigated it much. I've looked for Vacuum leaks but have not found any in the places I know to look.

Here is a datalog: www.camaroz28.com/forums/lt1-based-engine-tech-9/help-datamaster-ee-analysis-log-included-856339/

The motor ran fine for a while, but now the noise starts at 2000 rpm or so and gets louder above that.

Here is the video: LT1 Engine Knock.. Need help figuring out what is causing it - YouTube

Also, I pulled the rockers and all the pushrods are straight as can be. I was hoping for an easy fix

Thanks for any help you folks can provide.

 

We're you able to set zero lash on all of the rockers? If you were to push down on each pushrod by hand, were you able to at all, or no? It really sounds like a spongy lifter to me. I have a much worse noise than that, which I was hoping was a lifter but was not. If it is just a lifter, that's not a terribly hard repair. I picked a set up for about $110.

 

Thanks for the reply.

I heard similar suggestions from friends/coworkers.

I have a set of lifters in the mail. I pulled the pushrods, but did not really know what to look for when pushing on them. I have not reinstalled them yet, so I'm not sure how the 0 lashing will work out.

For $120 from Jegs I got some LS7 lifters that I read were good to use instead of the comp camps ones for stock cam/spring applications. I'll see how they work out. 70kmi on the motor, I'm not going to put old ones back in.

 

Realistically there's nothing wrong with stock lifters despite what you might think of as "high" mileage. In fact I'd consider them ideal for your situation.

 

Agreed, I went with a new set of stockers

 

That's not a lifter sound....as odd as it seems, that sounds like an exhaust leak.

Lifter noise is a tap, like a drum stick on sheet metal. A rod or main knock is a heavy metallic sound like a hammer on a block....

I wouldn't bother installing new lifters...send 'em back for a refund. If they were th old flat tappet style I'd agree with the swap...but not rollers.

good luck...

 

Bw, I don't think a lifter or lobe is worn, but I think there is a definite possibility of a partially collapsed lifter. Just found one on mine. Only costs 15 bucks in gaskets to visibly confirm

 

Sure, it could be....it's pretty hard to diagnose a sound from a YouTube clip on an iPad listened to in an airport..chuckle.

I guess I would still start with an exhaust leak since he has headers. If the OP can just lay a wrench on the header bolts to see if they're tight, he'll have an indication of whether a leaky gasket is a possibility.....

 

Kinda sounds like a rocker arm on my brother camaro....he has the same kinda sound.
I recently had an exhaust leak but it sounded like a rod knocking on the pass side. ended up being the collector gasket blew out the top and exhaust was blowing out against the bottom of the car(floor board). With all that said, double check the headers, they can make odd sounds.

 

Thanks for the replies.

I FINALLY go the lifters swapped out. I think the noise is still there, but I'll be putting the accessories back on it tonight and taking it for a drive.

At least I learned how to swap them... I have torn a motor down before, but not built one back up, so I'm that much closer to that experience.

Valves are all re-lashed in, and 10 or so hours was wasted, but at least I have ruled them out.

The rockers all seemed fine, one valve guide had a tiny bit of play more than the others, but not terribly concerning.

I'm back around to checking for exhaust or vacuum problems

I'll update when I know more for historical sake.

 

As much as I'd like to just bow my head in shame and never be seen again, I have to admit I fixed the problem.

Loose header bolt. It finally backed out enough for me to see it, it was the back-most driver's side bolt.

$100 and 8+ hours of work later, I tightened the bolt and the motor is (was) running well. My new thread is here with an unrelated problem:

http://www.camaroz28.com/forums/lt1-...rt-now-867137/