0352Marine

Ok guys I just want some opinions on what would cause this failure. Only the #1 rod Bearing spun and about four other rod bearings look like one with wear on the top and bottom of the bearing. I’m not going give my opinion but I would like for other expert engine builders or LS engine builders tell me their opinion. Engine is a LQ9. stock crankshaft, gen 4 rods. Flattop pistons. Bore is stock 4”. Bearing clearance was between .0015”- .002”. Compression ratio was calculated to be 11to1. Pictured is the spun bearing along with another bearing. I want an opinion on both and a possible cause. Thanks


Outside of spun bearing

Different Bearing still inside the rod with increased wear marks on top and bottom but sides appear fine. Four other rod bearings looked like this one.

#1 piston rod bearing spun. Non of the other bearings spun

B52bombardier1

Oil starvation at high RPM??? That looks awful and must have made a lot of rod knock noise????

Rick

0352Marine

Well I thought that, but none of the other bearings were like that. The mains were fine which I would have thought that they would have some kinda damage.

Also I left out that the customer installed the engine into a truck and then failed to properly install everything and when he tried to start it it backfired several times and ran like **** until someone else pointed out that a ground wasn’t on. Then he fired it up and it ran fine until he rev’d it up to 1500. I’m thinking that this caused the spinning, based on the looks of the bearing in the rod it looks to me like detonation but unsure. Another four bearings looked like the one in the rod

kingtal0n

iTrader: (1)

what do I think happened, i think somebody tried to rebuild the engine
tell whoever did it not to try to rebuild LS engines unless they are an expert already from at least 5 to 10 previous failures and 2 to 3 good running rebuilds done already running for over 50k each in different cars and still driving. That seems to be the minimum around here


harsh but there are 99 failure rebuilds for every 1 good rebuild
and sometimes the "good" rebuilds are not better than stock
https://www.yellowbullet.com/forum/s....php?t=2401762

the machine work is often at fault or failure without the owner realizing
https://www.yellowbullet.com/forum/s...2527749&page=8

Okay down to business. First of all, diagnosing a blown engine without details is like diagnosing a person that can't talk or sign.
Usually if you want to know what happened, you have to look at the logs. Specifically, oil pressure logs, engine behavior logs.
These questions must be answered
1. When did it lose oil pressure (after how many miles/minutes of run time)
2. what is the complete history of the engine
3. was the engine pre-oiled using a compressed air canister after any rebuilding and verified to have oil pressure to the head at every rocker

Now, I don't expect you to have all that. I am merely pointing out that is makes life much easier to diagnose when you know the details.

Next, you can crank an engine with no fuel and the plugs out, and the oil pressure will build and protect it while it spins.
There is no way to damage an engine from just spinning it over, whether the engine is running or not, it shouldn matter as long as the oil is clean.

Finally, Rod bearing 1 is the last bearing to receive oil, so this is a big red sign that points to an oil flow/path/pressure issue. What the oil pressure says at the back of the block does not necessarily reflect the rod bearings supply of oil. I believe a spun cam bearing for example cam stifle the flow somehow. I am not an expert and I do not rebuild LS engines but I know that rod bearing #1 failures happen most often to engine rebuilt with too-loose clearances that are cold started frequently. Not saying this is your issue but it helps sometimes to consider similar circumstances. The reason they have trouble is I believe each bearing takes its share of oil and rod bearing #1 gets whatever is leftover at the end of it all... and if there isn't anything leftover then thats that

0352Marine

I don’t know the answer to when it lost oil pressure nor do I know how the engine was treated before the failure but I can tell you that I built the engine and this is approximately my 17th LS performance build with the first failure. The engine was prelube with a pressure canister which is how I fill the engine up with oil. The oil was a break in oil. I try and follow the same procedures for each build but that’s not to say that I’m perfect because I’m far from it. I’m not going to acknowledge anyone on here who wants to be an *******. I know that this journal is the last to receive oil and generally I don’t go past 0.0025” bearing clearance. The only thing that I’m thinking that could’ve went wrong is the fact that the customer wanted to use the stock rod bolts and there is a possibility I may have tightened it too tight due to the process of torquing the bolts. I reconfigured the oiling system by removing the filter bypass and installing a metal barbell as I do with every engine. I also not only check the crankshaft myself but I send it to a crankshaft specialist who polishes the crankshaft cleans the crankshaft and journals and measures the specs. The oil pressure according to the customer never dropped below 40 psi. He said that he noticed the noise after he had taken it to a tuner after he had changed the injectors. I’m not trying to point the finger but it was running fine before then and I have no idea how high the tuner spun the engine

kingtal0n

iTrader: (1)

This is all relevant, important information that should have been in the original post.

Engine RPM and oil-bearing clearance seems like it is related. 8,000rpm, 9,000rpm, 15,000rpm, at some high enough rpm special considerations need to be made. But that is usually for racing engines trying for longevity around 9,000rpm to 15,000rpm ranges mostly. I feel It is possible to have 40 or even 80psi of oil pressure on the gauge reading from the back of the block and still starve rod bearings... I doubt that was the case here, I only mention for historical evidence. The modern trend is towards thinner oils w/ superior behavior in tighter bearing clearance, and then improvements to the pump head and orifices are adjusted to suite that exact task as time improves materials availability.

consider frequent oil-bearing factors which have consequences in oiling systems:
engine bearing clearance, engine oil viscosity, oil temperature, oil-engine interaction time, additives to oil or air which alter the oil, fraction of the time/face bearing is loaded, bearing/crevice shape & special characteristics (champhers, file lines, cuts and grooves), oiling orifice exposure time/frequency, variation in pump head & displacement due to temperature & viscosity changes(oil behavior as it warms vs oil pump conditional output features such as "pressure relief springs" can malfunction with a wide range of consequences, &c

there are so many things, just looking at an oil starved bearing and noting the fact that it is oil starved will not be enough evidence to do much with