Did detonation kill my bottom end?
 

Last fall I blew 5 out of the six head gaskets due to detonation. Rebuilt the top end and was running it in the shop last week when it suddenly locked up. Engine would not move either way. Pulled it out AGAIN and found two rods had spun the rod bearings. Numbers 3 and 4. I had gone to great lengths to insure I would always have oil to the rods. I had cross drilled the crank, grooved all of the main bearings and installed a 993 oil pump. It had good oil pressure when I was running it, ie 25 psi at idle.

I was wondering if this failure didn't start last fall when I detonated this 12.5:1 compression engine. Here are some pictures of the bearings,

http://forums.pelicanparts.com/uploa...1405185635.jpg
http://forums.pelicanparts.com/uploa...1405185668.jpg
http://forums.pelicanparts.com/uploa...1405185696.jpg

I don't see evidence of detonation on your bearings; I do see a lot of FOD caused by metallic debris and possible evidence of incorrectly sized big ends on the rods. I'd have to measure the latter to be sure.

Detonation manifests itself on piston crowns, ring lands, pin bores, upper rod bearing shells, as well as other places.

Steve hit it on the head.
My experience with detonation appears as craters on the tops of pistons...and when the pistons come out...the top ring is in 50 pieces!
I have seen rods damaged by extreme detonation...they were actually bent slightly sideways.
Also...the heads get the same treatment...cratering...valves bent sometimes....and the ends of the plugs can be melted or broken.
Bob

The FOD is from the bearings that spun. I had the rods resized and checked them with plastic gauge. Does the fact that the two outer most rods spun have any significance? What is odd is I didn't hear any knocking and it had good oil pressure.

High strung turbo engine, I talked to CCR Armando when I was telling him about a spun out #4 rod and he said to watch #3 when I open it Sure enough, #3 was getting to the point of failure. The owner commented on the oil pressure, now Rennsport is checking the pump
Bruce

I guess 3 and 4 are the weak links. I am going to have the machine shop check the good rods and see if they are correct. I hate not knowing what happened.

#2 & #5 are the weak links; i.e,..the last part of the whole engine to get any oil.

FOD shows up at #1 & #6, first. Doing the forensics is a very detailed complex process that also involves cutting the oil filter(s) open with a special cutter and laying the paper element out on a clean sheet of butcher paper to inspect everything VERY closely.

I don't have anywhere near enough information here to offer something constructive, but if you really want to know what happened and in what order, you need a pro who specializes in 911 race engines to do this.

I went to my machine shop today, bad parts in hand to discuss what happened. Looking at the bearings and the crankshaft my guy surmised the rod bearings did go dry. It was hard for me to believe since I had done so much work to get oil to the rods. He agreed but, pointed out all that work I did was the problem. The cross drilling of all the mains, grooving the main bearings, not running the restrictors in the heads and notching the rods to squirt the bottom of the pistons was all good....for over 4000 rpm running. It is all terrible for idle. He said this has been dying a slow death for some time. My oil pressure at idle was low but I thought that is what the sixes do. He said nothing lower than 20psi.

So a little medicine is good, a lot not so much.

To add more damage to my wallet he said I had to replace, not flush, all of my oil lines. He has seen the metal bits imbed themselves into the rubber liner only to come loose later. Oil cooler replace. Oil tank complete disassembly. Clean, clean, clean.

I feel he is correct The new crank I will cross drill the center bearing only, run the head restrictors and use a case with piston squirters not notched rods.

Hopefully, that is the last of this story.

You might think about getting a higher output pump too.
Turbo or late type pumps put out more volume.
Just make sure the case mod for oil bypass is done... and that the correct bypass valves are used.
Bob

I was running a 993 pump, but I thought the pressure side of this pump and a 4 rib were the same, only the scavange side was increased. The bypass mod was done and I had the correct bypass valves. I still think if I had used the oil line restrictors things may have been different.

Didn't you say it was 25psi @ idle?

Todd

Yes I did say that but rummaging through my old feeble mind that the 25 psi was at cold I had seen lower when hot.

There is one other possibility.
If you don't have enough side clearance on a rod...the oil flow is reduced.
You might have lots of pressure...but it is FLOW that gets the job done.
Just a thought.
Bob

I think the side clearance on the mains was the real issue, I don't think the rods saw the oil. A buddy of mine mentioned this is why the F1 engines idle at 9000 rpm.

This is interesting. I've checked rod side clearance in the past, but never really considered why. Neilca, I'm curious how the side clearance became reduced. Did you change rods or the crank at some point?

I had not checked the rod side clearance other than to make sure there was some. The rods and crank come from different engines originally. I will have to check this to see if it was a contributor.

Neilca,

I see some questions in the photos first you have grooves cut in all the mains, when cross drilling the crank I have seen the center main grooved AND the feed in the case bored a bit larger. Why are all the main bearings cut? What was done to the crank? What was drilled?

As Bob pointed out flow is what keeps things happy bearing wise. When you did your build what clearance did you go for on the rods? The side clearance is one "control point" but the bearing clearance is THE BIG control point. When set on the tight side I have seen some of what you show on the bearings.

If you have factory oil squirters in the case why did you add the rod notch? Install larger squirters, they limit low pressure flow the notch does not.

Steve always spot on knows this is a COMPLEX process. I am just trying to see where the mods came from that may or may not have contributed to the problem.

Yes all the mains were drilled and I drilled them all the way through. I was trying to maximize the oil flow to the rods. I built the engine two years ago so my recollection is a bit dimmed. I think the rods had a clearance of 0.0015. I do not remember the side clearance but I have to assume it was within spec.

The case did not have oil squirters thus the notches.

Neil,

Sorry to hear about your failure. I know the feeling. Been there done that on my last engine build. I quoted the above not to add insult to injury, but to reinforce the importance of cleaning everything. You can't risk an "encore presentation" like Steve often says. You have to clean absolutely everything. EVERYTHING.

Engine case needs nearly all the plugs pulled to get junk out of all the oil passage.

Factory oil tank can be ultrasonically done by aviation place like Pacific Oil Cooler or the like. Oil passages and the screen in the factory tank are big enough that ultrasonic will get it clean and it'll come back looking like new. I recall your oil tank is a Peterson style, so that should be easy peasy to clean yourself.

Oil cooler(s)? I wouldn't risk it. The passages in them are tight and I would think the potential for junk hiding in there is high and can dislodge in the future. Replacement coolers are expensive, sure. But a lot cheaper than another smoked engine.

Oil lines? Yep. Take all your braided stainless hose and junk it. At least you can reuse the fittings.

Crack open your thermostat(s) and clean those. I found all sorts of FOD in my factory '78 external t-stat that would just be waiting to trash my "new" engine.

Your oil pump may feel like its OK. I bet if you open it up, it'll look like this:

http://forums.pelicanparts.com/911-engine-rebuilding-forum/706984-engine-bearing-failure-disassemble-heads-too-2.html#post7116651

Don't risk using that pump. I unfortunately think that 993 pump you have is another casualty. Retire it to the hall of shame.

Thoroughly clean the intermediate shaft inside.

Throw away your timing chains and look closely at the sprockets. The chains are junk IMO because bearing material gets embedded in the links & rollers and can flake off later on if re-used.

Take a look at the cam housings and make sure they're still OK. Bearing FOD can get up there and score the cam bearing bores and also plug the cam & rocker spray bar. You should remove the spray bar end plugs, pull out the tube (note orientation of tube) and thorougly clean the tube & larger oiling passages for the cam bearings.

Don't forget the cam housing oil feed lines that feed from the engine case to the banjo adapter. I would replace them to be honest, since there's a rubber section in them. Or have a hose shop crimp new rubber sections into them. Can also make them out of AN-4 hose & adapter fittings. But then you're just spending more money.....

Don't overlook anything that oil comes in contact with. The FOD gets everywhere.

Where's the blueing and heat if it was short on oil?

That is the funny thing about this failure, it was failing at idle. Very little heat build up. High RPM I had tons of oil flowing. Funny I never heard any knocking either.

It seized up without any heat showing in the bearings? Are there any metal deposits on the crankshaft?

http://forums.pelicanparts.com/uploa...1407681251.jpg


These are the bearings that seized the engine. I have placed them how I found them in the rod. The rod did not have much bluing but as you can see the bearings spun. I have already replace the oil cooler, oil lines and am in the process of cleaning out the cases. I have procured another crank and rods, bearings, chains, oil pump. I am personally bringing this country out of the recession. :D

Hello just wondering if there were any updates to the forensics done to determine cause of the bearing damage?

I am not sure if it was mods I made to the crank or bad rod bearings. See the postings on the Glyco bearings for the 2.4 rod bearings. Either way the new engine will have a 2.0 crank and no mods.