LT1 Knocking / Metallic Flakes in Oil
 

1997 Z28, just about to clock 100k. Motor was rebuilt 25k ago due to a bent rod. No mods beyond a CAI or catback.

I'll try my best to describe what's going on, trying to determine how serious my issue is and whether or not it will make 400mi from PA to NJ w/o total destruction.

Car sees regular oil changes between 3,000 to 5,000 miles of fully synthetic oils. It has an oil leak somewhere on the back of the motor already.

I changed the oil about 2 weeks ago and knew something was wrong right away because there was an odd film on the surface. While pouring the old oil back into a container to dispose of it with, I found a bunch of small metallic looking flakes in the pan. This is the first time I have ever found anything but used oil in my pan. There were quite a few pieces, I'd describe it like when you watch people pan for gold. There were also 2 small pieces larger than the rest, like maybe 0.5-1mm

I had a friend help me as I thought the oil change would be a quick, hassle-free job. He took care of cleaning the drain plug, but didn't bother to inspect it then left for night class (he did this before I found the specks throughout the oil, although he should have looked at it...). Haven't put more than 50 miles since changing the oil.

The car runs strong. No issues idling or accelerating. Oil pressure is about 60PSI cold, drops to around 20-25PSI hot. Currently running Pennzoil Platinum w/ K&N filter. Oil pressure is pretty consistent and doesn't really move around. I have seen it hiccup when hot once in a while (like a small drop, but goes back quickly), but I don't think that is a problem.

The only oddity I can find is a knocking/tapping that is real noticeable when cold, and sometimes seems to be there while hot too (I'll have to put more miles on and get the motor real hot and listen again). I used to think it was just piston slap, but now I'm not so sure.

The noise occurs around 1700 rpm and stays for a little bit as I accelerate. It sounds identical to a woodpecker and doesn't always occur every time I hit the gas, sometimes it stays for a bit, other times its there for a second or two. I would say it happens consistently when put in gear above first (2nd, 3rd, ..) when you apply a load on it. Didn't hear it in neutral (clutch in or out) or letting it idle.

Sorry for the long read, just trying to get enough information down.

Any suggestions of what it could be?

Ways to further diagnose or inspect?

Limited resources on campus in terms of automotive tools, can get hand tools and what not.

Thanks a ton in advance. Ideally I'd like to just get it home, don't have the money or any trusted mechanics out here. Would prefer to do it at home and if its a doable project I'd like to do it myself or with help to learn.

Any way you can record a video of the noise?

- Justin

feasible to send oil out for an analysis? not too hard or expensive.

I will try, going to stick a camera under the hood and see if I can't get some sound as well as get some from inside the cabin.

If I knew about it earlier I would have. More than likely, I'll be changing it again before I attempt to make a trip to NJ. If I find more, I will see if I can find a place to analyze it.

Start you tube searching for rod knock video clips, then compare to yours.

Could just be a gummy lifter, or loose rocker. Impossible to say via internet words. Can you find a mechanic stethoscope and probe around to see where the sound is originating?

Ya you're on borrowed time. I'd throw a $5 on rod knock/bearing material.

2 quarts of lucas oil

Do you have the old filter by chance? If so cut it open and see how much "stuff" is initiative. But that much metal sound like babbitt off the bearings. Knocking could be allot of things, metal in the oil is never good.

BTW Where inPA are you?

Find anything out?

Haven't had much time between projects/classes to do too much with it. I have driven it here and there, with the warmer temperatures it doesn't seem to be there as much. Still have to capture audio of it though.

I did watch several YouTube "LT1 Rod Knock" clips and it doesn't sound like that. The knock/tap is mostly audible around 2k and seems to go away (or there's too much outside noise to hear it)

Beaver County, pretty much 6mi or so from Ohio

I second Lucas oil and some 20W50 if it is a rod knock!

So ... 3000 miles later and the car has not exploded. Resealed the intake from an oil leak and did an oil change around 500 miles ago.. threw in 10w30 Castrol conventional oil. Didn't find anything like last time. I don't hear that horrible noise now with the heat and thicker oil. I do notice a slight hiccup on the oil pressure gauge after the engine is at operating temperature while idling. Steady 20-22psi at hot idle, 40-42 driving normal/highway and up to 60 cold or heavy acceleration. Didn't find anything in the lifter valley, all the push rods seemed snug with no excessive play.

Nothing I can do or easily spot without tearing the thing apart, think Ill wait til she explodes.

Interesting. Odd that it went away... I wouldn't use a K&N filter if I were you though... they are garbage. Maybe some left over stuff from the rebuild? :P

Is this from experience?

K&n along with wix is supposed to be very good filters, maybe u have it mixed up with fram

I remember seeing some articles about rating oil filters and K&N/fram were at the bottom. top were AcDelco and mobil1. *shrug*

That's pretty curious because K&N and Mobil 1 are both made by Champion Labs and are virtually (if not entirely) identical besides the nut on the bottom. Champion also makes AcDelco, STP, SuperTech, etc. FRAM filters were unpopular for a while, so maybe you were just thinking of that.

Apparently now (2010-ish) Champion and the division of Honeywell that produces Fram/Autolite/Prestone stuff have both been purchased by someone else who is merging all the filter programs together so maybe things have/will change.

I run fram filters on my dd pos. on my ta i use mainly wix