Guys, I Need some help with a sick bird. Back in September, the GTA started making this noise when it gets warm. I've finally got around to trying to fix the problem. I drove it from Florida to Houston and back like this in October, and it didn't crap out, so I'm assuming its not a major issue.



The noise is only present when the vehicle is warm. It's most pronounced when the engine RPMs are decelerating immediately after being revved. It's not nearly as pronounced when RPMs are accelerating or the vehicle is under load. It sounds like an exhaust leak, but it does not get louder under load like an exhaust leak will.



I counted the noise at idle, at it ticks one time for every two engine revolutions (noise = 350 clicks per minute @ 700 RPM). I thought it was in the valvetrain. I tore the engine down this weekend, replaced all the lifters with brand new AC Delco LS lifters, cleaned out all the pushrods, and rocker arms, and installed new valve seals and new intake manifold seals. I got it all put back together last night, and the noise hasn't changed at all.



Oil pressure is a steady 35-45psi, as this engine has always held. It is bone stock other than the addition of headers.



I'm attaching two videos. The 1st is a cold start showing the lack of noise. The 2nd video starts 6 minutes after the 1st video ends, once the engine is up to operating temperature. The noise is clearly audible. Anyone run into something like this before?


Video 1:
Video 2:

 

sounds kind of like a loose rocker to me?

 

Rockers were all readjusted after installing the new lifters and valveseals. I took the entire valvetrain apart and put it back together again and the noise didn't change a bit.

Yesterday morning:

 

Have you tried taking a small hose to your ear and checking around the exhaust and head to try and pin point where the noise is coming from. Works like a stethoscope.

 

I think its a exhaust leak starting but its so small right now only condition must be just right to here it cause its just starting to leak member this happen to a car awhile ago just cant place what it was at the moment I will think about that and ask my buddy at shop to try and recall what it was

 

Distributor components?? Cap and rotor all look good? Just a thought

 

Simple stuff to check..

Warm it up then run it without the serp belt for a moment to eliminate possible accessory noise?

Disconnect injectors one at a time when hot?

Dumb but run in dark look for spark jump?

 

Thanks for the suggestions guys, but I'm 99% positive I've eliminated that stuff already. Someone in a local club suggested that I could have a broken damper valve spring. Anyone think that could be the case?

Ignitions system is 2 years old. Moroso 40 ohm 8.65mm plug wires, MSD distributor cap and rotor, NGK plugs, MSD coil (was on the car when I got it), and a new GM ignitions module.

I don't have a stethoscope, but I've been using a 2ft long forged socket wrench and my right ear as a makeshift one. The noise is much louder in the passenger side head than the drivers side head. It is also much louder in the header tubes than in the intake base or runners. No noise whatsoever is transmitted through the alternator, power steering pump, or AC compressor. No noise is transmitted through the valve covers either that I can pick up. There is a clearly transmitted metallic click when I listen to the passenger header tubes, I mean really, really clear.

Still working on getting the injectors disconnected one at a time. I started with unplugging plug wires, but I've run into some other problem while I was at it. I pulled the #8 wire and started it warm, noise was the same. I replaced the #8 and pulled the #6 wire and started it, noise was the same. When I replaced #6 and took off #4, the engine refused to start. I let it sit for 3 hrs, disconnected the battery, etc. No joy, it's not even trying to fire. I think I might have fried the ignition module or coil. I'm going to test for spark today, and then start replacing components with known good spares.

Once I get it running again, I'll finish the cylinder test, and I'll do a vacuum test on it as well.

 

Sounds like an exhaust leak to me.

 

Have you ever had an exhaust leak that stopped making noise under load? I've had a lot of exhaust leaks before, but they always got far worse under load than under low MAP or low load situations.

 

In fact I have had one very close to that, it was a cheap paper header gasket that burnt and split. It was the oddest thing. It was worse at coasting than it was under full load.

 

do you have any oil pressure fluxuation. sorry for the spelling. might be a main bearing spinning in the middle of the block. have you checked the crankshaft end play. take a small pry bar and see if you have any movement, this can be done by removing the trans cover and see how much play you have in between the block and flexplate and then move the other way toward the front of engine. there should not be alot of play. also cut open your oil filter and see if you have alot of metal in the filter. also check your torque convertor bolts and make sure they are tight also look at flex plate for cracks. they sound almost like a rod knock some times.

 

also min. oil pressure per GM is min 10psi per 1k RPM so at 4500 RPM min oil pressure must be 45 psi and so on so if your are rev'ing your motor above 4500 and your oil pressure is not rising you will do some internal damage. how many miles are on your engine. but first check for noise on the bottom put a stick and listen for noise in the bottom end try running a little thicker weight oil and see if the noise goes away. older engines need a little thicker oil when they get high mileage on them. your car is 20+ yrs i would run a 15/40 ,if your not the first owner you can bet someone has drove the hell out of it to have fun we all do but how much is the question.
put a 5/8 socket on the balancer bolt and turn it back and forth and listen and feel for worn bearings you will feel it if there is alpt of wear

 

Night Rider,

I'll have to pull off the header gaskets and take a look. I'm using Percy's Seal-4-Good Aluminum gaskets, and it doesn't sound like any exhaust leak I've ever heard before, but I will check to be certain.

Oil pressure is good, 35psi at hot idle, up to 45 psi above idle or cold idle, and no fluctuations. It's a factory pump, it's not going to move much more than 45psi of oil. Factory GM service manual calls for a minimum of 10lbs at 500rpm and 30-55 psi above idle. I've run 10W-30 and 20W-50, no change in the noise. No change in the noise with a fresh oil change either.

I've shut down every cylinder one by one, and there wasn't any change in the noise. The noise does seem to get worse as timing is advanced though, so there's something.

 

have you check the flex plate (or flywheel) or the torque convertor bolts?

 

depends on what manual and when it published for oil pressure. any just to be on the safe side have you put a manual oil pressure gauge at the oil filter allen plug and the one at the top of block where your sensor is now just to verify

 

Definitely check your gaskets. Several times I've thought that I had a bad lifter and it was a blown header gasket.

Especially, since you mentioned it's very noticeable in the header tube. If you have a broken valve spring, bent push rod, the car will run noticeably different. So I don't think that's it.

 

Came back to this thread to reference the noise I had on this motor while troubleshooting with an 8.1 swap that I'm working on. I didn't realize I'd never closed this out with the resolution.

In case anyone has wondered over the years what I found, it was a badly spun #2 rod bearing. Ruined both the rod and the crank. I ended up doing a complete rebuild before selling the car back in 2016.

 

We call that the back rattle - that's a typical rod bearing sound. Best thing to do is cut the oil filter for inspection when you get into noise diagnostics. Usually rules out or confirms internal problems pretty quickly.
GD