'97 Z28 LT1 automatic, 129,000 miles, Castrol GTX 10W30. Motor developed what sounds like a loud chirp. It sounds like it is coming from the intake manifold. It is not a clunk like a bearing. It is a regular noise and the frequency increases with RPM. I pulled the valve covers off. All the rockers are getting oil. Oil is a little on the slow side getting to the top, but not alarming and doesn't effect the noise. I unplugged each spark plug wire and it doesn't change. If you drive it at interstate speed in regular drive (around 3300 rpm) for a while it quiets down 95% for a few days. Is there anything in the intake or emissions that can cause this? I have an opportunity to purchase an LT1 from a '95 Trans Am that was wrecked with 16,000 miles on the clock for $800. (from a trusted individual) No intake or opti-spark. The individual bought it with intentions of putting it in a street rod with a distributor but changed his mind.

 

From here it sounds like it could be a vacuum leak. If you have a propane torch, open the valve some (don't light it) and with engine running, move the tip around to different areas like intake manifold to head, where throttle body bolts on, etc. If the idle speeds up, you found the leak. If you don't have a torch, you can use what some other guys like to use; highly flammable spray solvents that can also eat away at/ruin painted surfaces.

 

If it is not a vacuum leak, you may want to look at your valve lifters. I had a lifter roller seize and chew up a cam lobe. Loud squeak and hard to pin down, except that it was louder if listening to the engine from the oil filler opening.

 

The noise has been gone for the past 4 days. It started almost a year and 1,000 miles ago. I just haven't driven it much. I am going to pick the replacement motor up on Thursday. I think $800 is a fair price for an LT1 with 16k miles. No optispark or intake, but I already have that.

 

i have heard of starters rubbing the flywheel and making that noise. how is the oil pressure and has it been dropping or raising any?

 

Oil pressure is the same as when I bought the car 5 years ago. I run Castrol 10w30. Just over 40 on a cold motor. 210 degrees at idle stopped in traffic in drive runs around 15-18. Doesn't bounce, just gets lower with temperature. I did pull the dust cover off the transmission to check the torque converter bolts, and I didn't see any rub marks on the flywheel. Good thinking though. It couldn't be that easy!

 

have you unhooked the fan/drive belt to see if anything run by it is doing it. alt, power steering, a/c. noises like that can travel through steel and sound like its from elsewhere. lol now it won't do it. over 200k miles with these engines is common. my first was still going strong at 200k

 

If you think it is lifter there should be a lot of metal flakes in the oil filter. If the filter is clean you need to keep looking. Noises like this can be tuff sometime. Sound traveling through solids can be very deceiving.

I had a sound the other day that I was sure was a major lifter issue in a 5.3. It sure sounded like a lifter but the more I listened the more I thought the rhythm was off. Turn out to be the AC belt coming apart, a piece was slapping the side of the motor. It was a $11 fix.

 

that low of miles ,yes buy it ,then if you can find the problem ,you still got a good low miles engine ,knowing the person is good to,i was going to buy a lt1 engine when my head..gasket. went ,it had .18.000 but I did not know the person ,,I am sure I could have got .more miles out of mine.the car ma.y owe you nothing ,yes those noices can be small ,I thought I had a .valve.hiting ,was cover on the back of my .alternator,,an earatating sound to ,for me its at lights got this fine car making this pinging noise

 

I would remove the accessory belt and see if the noise stops. Next i would use an auto stethoscope to listen and location the source of the noise (Hobo Fake <$10).
I was surprised once to find the trans flywheel inspection cover on my manual trans corvette has a bent ear that sounded just like a rod knock - the crank flange was hitting the inspection cover bent ear.

Congrats on a good deal for a spare motor. I hope it has the low miles as mentioned. I would prefer to listen to a motor run before purchase.

Good luck.