Not chain ramps! - investigating rod bearing issue, whats this in my oil?
 

Hi all, looking for help with weird scenario. Some back story first.
- '86 3.2 engine, PO rebuilt with <10k on rebuild. Looks like rebuild focused on heads, valves, guides done etc. Pretty sure bottom end was left alone. Oil pressure good, pegged at 100 on press gauge at 3k RPM car at 210* temp.
- Oil change ~ 600 miles ago (Brad Penn), no bits on magnetic oil plug save for very little grey sludge.
- In the past week or so I have been doing some runs with the PerfExpert smart phone app and hit rev limiter briefly in 2nd gear couple of times, oil always up to op temp. Yesterday after a run parked it, all seemed fine. 3 hours later started it to drive into garage and knocking noise. Engine was running with the noise for about 5 minutes while I listened in horror. It didn't seem like valve train, not linked to any particular side, more from middle of engine. Quite a hollow knock sound - rod bearing says I.
- So today I pulled the engine oil plug and strained it through some paper shop towel. The following pics show what I found in there. The oil plug was as seen in the pic below, no metal bits, maybe a very light misting of the grey sludge.
- So what could these black pieces be? They are not metal, carbon?. I was able to crush one piece with a spoon, just crumbled up.
- And more importantly as there are no metal pieces on the oil plug is it safe to assume no bearing failure? Or did I shut it down soon enough that the damage didn't get as far as the oil plug?

- What should I do next? Thank you in advance...

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Take any videos ?

have the oil analyzed?

I'd say carbon except a piece that large wouldn't get past a piston. Chain ramp maybe?

Borrow or get a Video Scope from HB, and inspect each cylinder via spark plug holes

looks like a chain ramp. almost certain. there is no other black plastic inside the engine,
dont start it.
if you work on your own car its doable and probably fiddly.
i would say ur ok as long as the timing chain didnt move a tooth

Actually no, silly in retrospect. But I was too shocked to be honest.

Yes, I have the oil in a bucket. Will send some out, thanks.

Ok, I have a video scope. I'll take a look in there for debris. Good Idea.

I'll do some research on the chain ramps. If its that I hope it didn't jump a tooth, guessing that could give me bent valves.

Would valves hitting a piston tie in with the hollow knocking sound that I heard? Is it possible that a ramp would break following some trauma in a cylinder (like a broken spring or dropped valve)?

Thank you all for your suggestions.

No not valves but broken ramps or loose chain, hollow knocking or empty metal trash can sound? Yes, it is possible.

Agree with a prior post, looks like a cam chain rail failure. Knock is likely heard at the back of the car right or left side of the engine fan. I doubt it's knocking on both sides, take a long screw driver put the handle against your ear and touch the end of the driver to the area near the chains. LHS behind the distributor and then RHS near the AC compressor. Does it sound a lot louder on one side?

The noise seemed to be coming from the middle, almost like under the throttle body but inside the block. Hence my thought of a rod bearing. I'll look into the cylinders through the plug holes and hopefully see no damage to the pistons. To inspect the chain ramps am I looking at a partial engine drop?

This is a chain ramp
Porsche 911 Cam Chain Ramp Thin Brown 1 per Engine 911 105 222 05 | eBay
Look for more pics of a chain ramp on google.

Is the material dark brown in color?

And the winner is, timing chain ramps.

If you see any damage to the timing chain housings you would be wise to take it apart and clean all the oil passages out, especially the crank.

I just spent $8k rebuilding someone else's rebuild because they tried to save a few bucks.

No it's definitely black in color.

It is pretty easy when doing a DIY rebuild to improperly install the chain ramps. They can be fiddly.

It is feasible, as mentioned above, to replace them with engine in-situ.

Knocking sound could be some remaining chunk of chain ramp getting knocked around in the sump area. Still, I would second the suggestion to get an oil analysis done (if you dumped the oil into a clean bucket).

In the meantime, pull your oil filter and cut it apart, and take a look for rod bearing material in the pleats of the filter (you'll be seeing more of that black plastic material too). Was the sound a very regular rhythmic knock, or more like dropping a spoon into a garbage disposal kind of random and chaotic?

The OP rebuild was done by a race shop, so I guess they knew what they were doing.

And the sound was rhythmical not random. Would metal particles make it to the filter before the engine oil drain plug? I'll pull that tomorrow and check it out.

Thanks again for all the suggestions.

Sorry, for some reason I got into my head that the previous rebuild was DIY.

Rod bearing particulate wouldn't cling to the drain plug as they are non-ferrous.

Picking up an engine stethoscope from Sears for a few bucks might be a good investment if there's no 'glitter' in the oil filter pleats. After checking the filter, and also checking on the chain guides, that is. They are worth their weight in gold for tracking down noises. I've had three engines on my lift making scary rod knock noises, and in each case the stethoscope helped me diagnose an issue that was up in the (far less expensive) top end.

Just pull the timing chain covers for a look. Should be able to get in there with just tin removal and maybe a partial engine drop. Good luck.