I Have a 1995 Z28 and it is making a knocking noise from around the oilpan..I know its not the flywheel or torque converter...any suggestions?

 

does the knocking increase with the rpms? If so, sounds like a spun rod bearing (aka rod knock).

time for a rebuild.

 

Its not a continouos knock. If i put the car in drive or reverse, it wont knock at first. Its weird, sometimes it will knock and then somtimes it wont knock at times.

 

That does not mean it not rod knock. You need to do some more investigating.

 

Check your oil! It definitely seems like you have a knock of some sort. What kind of gas are you using?

 

I just use the regular gas. I dont think its the gas though b/c the car had been sittin up for about 6 months and some of the motor was takin apart to change out the heads and i had it put back together at a shop. I went to the beach and came back and stopped at a store and when i put it in park it started makin the knockin. Would too much oil make it knock?

 

Poor quality fuel will make it detonate under load.... that is called spark "knock". And the PCM uses the knock sensor to eliminate that kind of knock when you are using poor quality fuel. Your LT1 makes best power on 91-octane or higher. Using regular grade fuel won't hurt anything, but the engine will probably see a power loss.

But that does not sound like what you are hearing. Sounds like you hear a knocking sound, at the bottom of the engine, when its idling. That is not spark knock and not related to fuel quality. It may be related to oil quality. What grade/visosity oil are you using? What does the oil pressure gauge indicate at idle? When was the oil changed last? Have you checked the oil level? Is it possible the oil has been diluted by fuel with the engine running excessively rich? When you smell the oil, does it smell like gasoline?

Overfilling the oil can cause the crank to whip up the oil and mix it with air. Circulating air-entrained oil will cause knocking, since it is not a good lubricant and can not maintain the required oil film thickness in the bearings. It damages the bearings, which can cause them to knock.

Changing the heads does not require the bottom end of the engine to be "taken apart".

 

I use 10w-40 and i changed it not even a month ago but i drained it all back out and the oil was kinda brown and it seemed like it had a little water but i didnt see any metal shavings

 

You aren't going to necessarily find metal shavings with worn bearings. What you will find is high content of certain metals in the oil. You have to have a used oil chemical analysis done to find it. You also have to cut the oil filter open, using something other than a saw (creates particles), and open up the pleated paper to look for particles.

 

It wouldnt be a bad knock sensor would it?

 

Is it knocking only with the engine under heavy load (spark knock)? Or does it knock when the engine is under no load (bearing knock or piston slap)? Does it vary with engine temperature? The LT1's hypereutectic pistons are known for their piston slap when cold.... mine did it from the day it left the factory. Doesn't hurt anything, and its not abnormal, but its annoying. Lasted for a minute or two on cold start.

If you have a faulty knock sensor, the PCM retards the timing to prevent detonation/knock, so its unlikely a faulty knock sensor would cause the problem.

 

i hadnt left it crunk up for long but when i first crank it up it wont knock for a few seconds

 

that's kinda how mine was when the motor ate a bearing

wouldn't knock until it ran for like 4-5min

 

Yea..does anybody know anything about it possibly being a wrist pin?

 

That falls under the category of what Fred already covered. Pretty much it could be a wrist pin slapping, or piston slap. If is is a wrist pin you are likely damaging the cylinder walls. You need to dig further to complete your investigation. We can tell you what it sounds like, but that is not comparable to actually putting our hands on it. Even to the experienced mecahnic it could still fall into any of the categories listed above, the best way is to try and isolate the problem and then narrow down your choices. Try using a length of hose as a stethoscope to listen to where the noise is most prominent, being careful of rotating parts while doing so.