I was driving my 95 lt11 z28 and noticed a knocking like a exhaust leak. I pulled over and popped the hood and while idle there was no noise but at 1500 rpm a knocking sound not sure if it topside or bottom. while driving it it only knocks when reving to shift ...Rod Bearing??? Also if it is a rod bearing i am on a limited budget, What kinda cost am i looking at to replace a rodbearing and can just the one bad be replaced?

 

I suppose step one is to diagnose the issue.
Is it a knock or a tick? and where specifically do you hear it? (use a section of hose like a stethescope to isolate it)
If you do not have the means or expertise available to diagnose the issue, see a trusted mechanic.

If it is in fact a rod bearing, the motor has to come out and be disassembled, checked,
possibly machined to repair any damage then properly reassembled. New gaskets, new
fluids on top of the cost of the bearings ($75). There's no point in only doing one, the
cost of bearings is minor in the grand scheme of the project. In some cases the
cost of repairing the damage is enough to justify purchasing a used Lt1 motor instead.
(There's no shortage of used shortblocks around here, but be sure that you are
purchasing from a trusted source and that it is checked by a qualified mechanic; ask me how I know)
On the bright side, it is an excuse to step into a 355 or 383. Pick up some power for your trouble.

 

A rod knock has a pretty deep sound that should be discernable from a tick.

 

Its a knock for sure and gets faster with the rpm but is not constant. sounds like its coming from the right side of the motor. It only knocks when it is reving.Other than the knock it runs good and idles no prob. if it was a rod bearing wouldnt it be constant

 

Also stops knocking, knocks when it is reving to shift and in park when you reach about 1500 rpm

 

A rod knock may/may not be constant. It really depends on how bad it is. The more you operate it with a bad bearing, the more damage there will be to the crank, possibly causing the need for it's replacement.

 

Okay i stopped driving it and tomorrow gonna try and see exactly where the knock is coming from. Is it true i can disconnect one plug wire at a time to see if it settles down, then i know what cylinder it is or even is it is a rod and if not what else can cause this. If it is a rod bearing and i have to have a mech. replace all bearings what is a fair price i can expect.

 

you sure its not an exhaust leak around the manifold or hedder??? try checking that and it could be a rocker arm or roller rocker that is loose i would check them too.

 

yea you could also pull wires one by one to see if there is any carbon build up on any of the plugs. If there is then its an exhaust leak and you'll just need to fix that whether is a bolt or bad gasket. Mine was having the same problem sounds like.. coming from only one side of the engine. I could only tell when i checked the plugs to see if there was dark discoloration from an exhaust leak.

 

It was very easy to tell when I spun a bearing and threw a rod. I never heard any exhaust leak that even came close to the sound wich was def a deep knock.