I've been an LT1 owner for 1 year now so I'm still learning the in's and out's of them. My car is a 1995 and completely stock, just approaching 60,000 miles. My car has developed a ticking noise the past couple of months. It does not really effect the driveability of the car in any way. I think it has something to do with the exhaust in some way. The previous owner drove the car something like 3000 miles the 3-4 years before I bought it so something could be rusted/rotted/ or just wore out from sitting a lot.

My brother is a mechanic and took a listen holding a crow bar up to his ear while leaning on various parts of the engine. He said the sound is most prominent when he put the crowbar on the part I circled below (what is that called by the way?).



The ticking is not there when the car is first started and cold. It only appears after the car has come to temperature (half way up the temp gauge and/or more). The ticking is strongest at 900-1000 RPMs. Kinda seems to go up with RPMs but you hear it less as the engine spins louder than the ticks. It sounds like you would be tapping your fingernail on a table lightly.

Any thoughts are appreciated! It is quite annoying!

 

That is part of the AIR system. My 94 does that I believe it to be an exhaust leak.

 

I think those are AIR check valves. Maybe they are stuck.

 

The noise is not there when the engine is first started, because the AIR pump is forcing air through the check valves, and preventing it from ticking in response to back pressure in the exhaust.

To determine if the tick is going to cause a problem, feel the rubber 90* elbow that connects to the check valve. If that elbow is extremely hot, it may indicate the check valve is sticking open, and allowing exhaust to flow back into the piping and pump. Eventually the pump rusts up, draws excessive current, blows the fuse and turns on the SES light. A check valve stuck open can also allow the exhaust to pull air into the manifolds, and that will screw up the O2 sensor readings and cause that bank of the engine to run rich.

 

Well, replaced the check valve and the ticking continues. Darn.

Will have to investigate further to figure it out. Maybe I'll have good news in a few weeks.

 

Was the hose extremely hot or melted? If it wasn't, the check valve was not likely to be the problem.

 

No, hose was just warm/hot and not super hot.

We'll find out what it is some day here.