Knocking (Rod knock?) '95 w/ 3.1 V6

Hello, I have a knocking problem that I cannot figure out. I don't know if it is rod knock, but I will explain everything in a few paragraphs. I hope somebody with a lot of knowledge will take the time to read it all and try and help me out.

I have a 1995 Chevy Lumina with a 3.1L Vee 6 engine. I don't know a lot about cars, but what happened was, I bought a 2003 silverado, so i was going to sell the Lumina. I was driving the lumina to school and the head gasket went. I got laid off 2 days after I bought the truck, so I didn't have the money to pay to have the top end rebuilt, so I took on the venture myself.

I had a chiltons by my side, and talked with my girlfriends step-dad (who lives 60 miles away) and took on the enormous task (well... enormous to somebody who never even changed their own oil)... I read a lot online, read stuff at howstuffworks.com, and a lot of other websites. I rebuilt the engine myself, I used Anti-sieze on the bolts, used copper sealer on the head gaskets, had the heads finished, used RTV in the joints where i was afraid the gaskets might leak. I did everything I was supposed to. When I got it back together it wouldn't start. I tried everything, talked to a lot of people (my uncle, who is a couple thousand miles away) and couldn't figure anything out, other than speculation.

I had it towed to the local dealership and they said the computer was bad, so $500 later (keep in mind, i had no job, and a silverado payment) my car ran, but it know has a knocking sound that the dealership told me was probably rod knock. I didn't have the rocker arms/valves torqued properly, so I was just hoping that it was just the rocker arms making the noise. I got it home, and torqued the rocker arms down like my chiltons told me, and I still get a knocking. I have talked to my g/f's step-father again, and he says that he doubts it is rod knock because I didn't drive it but maybe 100 feet after the head gasket blew because the engine died. It didn't get hot enough for the rod to expand. Because the dealership said they thought it was rod knock, I had the rod bearings replaced (i don't have an engine lift, or know anything about the bottom end) (also, about the rod bearing fix, i know, it is known as only a temp fix, but i just wanted to sell the car because i was out of work). It didn't make ANY difference, this is another reason my g/f's step dad doesn't think it's rod knock.

It's too loud to be the water pump, I don't know what it is. I tore the valve covers off again to make SURE all the pushrods are properly seated in the lifters and that all the rocker arms are torqued properly, and they ARE. It still makes the noise.

I will try to describe the sound as well as i can in words. It knocks with every spark of one of the cylinders, and it will go away for 10-20 seconds every minute or so (which is even ANOTHER reason my g/f's step dad doesn't think it is rod knock). I don't know what else it could be. I don't know enough about engines to know if it is pre-ignition/detonation, or anything like that. I just know it doesn't sound good. I want to know if there's any way I can tell if it's a bad lifter, or anything else that might be easier to fix, without rebuilding the bottom (i don't have an engine lift, nor the money/time to rent one (btw, i'm working again trying to pay off the debt i built up while laid off))

Does anybody know if rod knock is something that would kind of come and go.

Also, if anybody's still here, one last symptom: the knock seems to be worse after the engine warms up.

Did you ever determine the source of the knocking?

I may have exactly the same pbm with my 95 Lumina
Thanks!

Your problems Sounds VERY much like a rod knock, you may have a SLIGHTLY bent push rod and sometimes it might sit just right where it will not knock where other times it could sit wrong and create the knocking sound. the easiest thing to do in this situation is to take all your pushrods out, find a nice FLAT table and roll your pushrods across them, childish as it may seem this is the easiest way to figure out if any of the pushrods are bent, if so go to an auto store and get a new pushrod (should be under 20 dollars). in worse cases you could have a bad valve On a cylinder head, a camshaft knock OR a crankshaft knock. camshafts are not REALLY expensive to replace if you go to a junkyard you can usually find one for under 50 dollars that is in perfectly good shape BUT they are dificult to replace, not as much as the crankshaft which would be a whole other problem. BUT i would first check all your pushrods for slight bend or curve in them.

Hello - I believe I have learned the hard way what your rod knock was..

I have a 98 Skylark with the 3.1 also... I had a leaky intake manifold which was seeping coolant.. tore it off to change gasket.
You see, the gasket on this engine requires the removal of the pushrods as the gasket is actually behind them. I reassembled and then had a clatter like no other... guess what I discovered when I tore it back apart? A few pushrods bent! Apparently the pushrods are different lengths and can be easily placed in wrong home. I was lucky and didnt bend valve. You might want to check that. Hope this helped.

Yes, check to make sure you ahve all the push rods in the correct places. They have red and blue lines painted on them. Im pretty sure the haynes says which is which.