Premature main engine bearing failure mystery
 

Long story of course but here's a summary: I had a very reputable performance engine builder rebuild my 502 rotating assemblies into 540's with Scat 1-42500 kits in 2013. He of course tanked the engines, spec'ed all the clearances, line-bored the cranks etc. Installed high flow oil pumps. All bearings and every internal engine part that moves was replaced. This is not a case of shortcuts taken or a shabby rebuild so please don't go there. . Originally used the stock remote oil lines, filter housing and cooler. After break-in switched to synthetic 20W-50 and started noticing oil temp went to 300+ deg after a hard run. Immediately swapped stock coolers to Revolution 3.5X18" coolers and oil temps normally ran 220 deg, never went above 260. This past summer I started noticing some loss in oil pressure so I did some research and swapped out the 3/8" oil lines for 12-AN. About a month after that both engines started to increasingly lose more oil pressure when hot. By the end of the summer the pressure dropped to less than 10 lbs at idle when hot so I pulled the engines and not surprisingly found severe bearing damage consistent with oil starvation. So the obvious conclusion might be that running the small stock diameter oil lines restricted the flow and is the cause of the bearing failure at less than 100 hrs. EXCEPT: how do you explain that the bypass valves in the block oil filter mount should have opened and shunted the oil directly back into the motors when the pressure differential got too high in the lines?? I change my oil approximately every 20-25 hours so there's no way there should have been enough normal combustion byproduct garbage in the unfiltered oil to trash the bearings after 90 hours. If the smaller oil lines are the culprit that's my fault and I can live with that, but I can't see how that was the cause given the fact that the bypass valves are engineered into these engines for that very reason. What I can't live with is not understanding what happened so I can make sure I don't make the same mistake again. Any thoughts or insights are appreciated-

damage to the bearings happened when it hit 300°,,after that,,it just was a matter of time.hi flow pump,small lines,,recipe for disaster.

Who made the recommendation to use the 3/8" oil lines?

A friend has about ten hours on his engines had about 10+ft of -8 oil line and hot oil went threw the cooler than to the oil filter. This motor was running by passing oil filter trashed the bearings. Btw 300degrees will start to take bearings apart. And bypass oil filter it will die soon.

I'm guessing he meant 5/8" not 3/8" stock oil lines. Regardless, too high an oil temp is clearances too tight, lean, too much timing or cooling issue of some sort.

BT

Were the Oil Filters Plumbed properly? Any and All filters flow from the Outside, In, Smoked the rotating Assy out of a Ford Sprintcar Engine 3 times , because the Oil Filter was plumbed backwards. The 300* oil didnt help , but it wont kill the bearings.

Upgrade your membership so you can post pictures or it's to difficult to diagnose all your problems.

Sometimes with so many lines, coolers, t-stats etc it is not out of the question to have that happen. I know it sounds ignorant but it's real world chit that can happen. I plumbed an engine with this that and the other thing and before installing filer I actually primed slowly just to make certain was A-OK. 300 deg for a very short period and mobile 1 for sure pushing limits but have heard of worse.

I like to keep oil temp gauge right next to pressure gauge. When I see engines with no temp gauges it makes me cringe.

I'll join you on that mistake but I only did it once.

Find out what bearings rookie used for your next time around also. He posted a pic of severely thrashed on engines and bearings looked perfect. Also as mentioned your lines are more than likely 5/8. Don't get down on yourself to much even though it sucks. It's how you handle it moving forward. Cooler and hose size and best oil you can buy. Also bearing clearance. What kind of water temps you running in? Stock 365 mag coolers in lake mi on a 500 hp engine I'd never see more than 250 even on the hardest running days.

First, thanks for the replies- I'm trying to get a handle on what happened and appreciate the input, but here's my response: First, I've done a lot of research on oil and temps. Bottom line- what I've found is that tests show synthetic oil can withstand occasional temperatures in excess of 300 deg, but the change interval should be shortened. The oil in these engines were exposed to those temperatures AT MOST 3 or 4 times for a period of no more than 1 minute each time. I changed the oil when I swapped out the oil coolers in 2013 and the oil temps never exceeded 260 after. I'm also not convinced that bearings will be damaged by exposure to 300 deg once or twice for a short interval. As to the oil lines: yes, I meant 3/8 but I'm talking ID, which is what Mercuriser stock engs come with. No one recommended these lines, I just reused the Merc parts. For the record, there was no engine temp/ cooling issues at any time, Timing and A/F mixture wouldn't cause bearing failure and they were never out of spec. The oil lines were absolutely with 100% certainty plumbed correctly.

I'm just a shade tree knuckle buster with mostly just googling skills and can't even haul gravel, but I've read plenty of problems here using only -10 lines with anything above 500hp. Remember that when those bypass valves are in use it dumps hot unfiltered oil back into the pan. More people have ruined a new motor with the stock bypass valve than hot oil here.

A high volume pump against stock lines may open that bypass valve and circulate unfiltered oil through the engine.

a lot of people THINK the 10 lb bypass ruined their engine,i know of several gen 6 marine engines with a 10 lb bypass that have run for years.just saying!

Who's oil filter you useing

So I get that sending some oil through the bypass un-cooled will raise the overall temp of the oil as measured by the thermostats located at then end of the first remote oil line, but the highest temp was never in excess of 260 deg, usually closer to 220 (except for 3 or 4 times for short periods before I changed the coolers). That means oil temp was not an issue and I still say that recycling unfiltered oil through a new engine for 90 hrs will not destroy a set of main bearings. I'm well aware that marine engines are different animals than car engines, but as a reality check: 90 hrs X 50mph = 4500 miles.

Post som pictures of your bearings. My thoughts on the bypass mode One something starts to fail it snowballs.

I started out using Mobil 1 filters and then switched to K&N. Used Amsoil 20w-50. With all due respect, I think the problem is not inferior filters or liquids, it takes something much more fundamental to cause a mechanical failure like this at 90 hrs.

My point is that cheap and small filters collapse inside shutting off oil flow and go into bypass mode and then you die.

well you don,t die,the engine dies and you live on to fix it,lol.

I only pulled the caps off and saw the #1 (forward most) main bearing on both engines. Both bearings had very visible wear. On one the surface was mostly worn down to the "copper" under-layer, on the other the outer silver colored layer was still intact but had may ruts running around the circumference of the surface.

Was it a std crank or a cut crank.

My point has nothing to do with oil temp, but that your oil was unfiltered, which is worse.

if this engine went 90 hours i doubt the bypass valve is the cause.

No argument. But in this case neither filter are in the "cheap' category and even if they were, I believe that it would take something on the order of at least a couple hundred hours of completely unfiltered and unchanged oil to trash the bearings. In this case even assuming the bypass valves opened, the the oil was at least partially filtered and was changed very frequently. These reply's have given me a few ideas to explore, which I appreciate, but I still don't think I know what caused this. I don't expect that the answer will be solved by discussing it with a limited amount of info and no photos but your suggestions at least give me ideas to think about. Thanks-

When the oil was running hot did the engines ever lose oil pressure? If it is only the #1 brg it could indicate low oil pressure. just a guess!

Both were factory new Scat cranks.

Engine shop by me will do a motor come back blown up he asks for the oil filter and it's collapsed in a few hundred miles.

i have seen a few big blocks that suffered a bearing spin from loss of oil pressure,the ones the farthest from the pump looked the worst.also took one apart that totally smoked the mains but never spun one.when the bearing trash flows through the engine the party is over.

unchanged unfiltered oil lasting 200 plus hours in a performance endurance marine engine,i don,t think so.

i overly rich condition can wipe out bearings in a hurry.

Newly rebuilt engine (why rebuilt something let go ) so the old oil coolers used or new ones installed ? and or restricted oil coolers (water side or oil side ) or oil coolers too small and lack enough cooling for the motor oil ?

Nobody is going to ask clearances and what oil pumps? I would look at that, then go from there... I personally am a fan of loose clearances, HV pumps and 20/50...I see 80 PSI under way even hot... and the lowest I ever see is 30 hot at idle... mains are .003-.0035 and rear is .004

This thread is eye opening and also making me a bit nervous with my motor

I don't believe the 300 degree oil temp hurt the bearings That being said I have build circle track engines for many years and have seen many of those engines well over 300 degrees and no bearing problems.

I would say debris and tight clearances may a good place to start.

You said it was line bored I Not a fan of just line boring main lines should be finished with an align hone period.

most say boring but it's usually a hone,its just happens.

Ok, couple of things, if you have any of the oil left from the engine get it analized for fuel contamination, as Mike said does not take much fuel in the oil to kill bearings in a hurry...I found out the hard way. If that is good, and you did not want to go there but could have been bearing clearance and or the cranks/rods not being round, all of this needs to be checked, have had great engine builders miss stuff before.
the factory oil cooler/lines/fittings on a 502 are a joke on anything but a stock one, all of the pieces need to be trashed, block adapter, filter adapter, cooler, lines, if you look at the merc stuff you will see why. My guy feeling is that the it was/is rich enough to have fuel kill it..

with 90 hours on it i doubt it was a clearance issue or a pump issue.not knowing what the oil looked like when the failure happened we are all guessing a this point. i don,t have a clue as to who the builder is but with 90 hours on the engine i would say he did his job correctly and the failure might have been caused by a parts failure or some damage that started when the oil temp was in the 300 degree area.

what is it that makes you nervous with your build?

OK, to try to answer several of these posts: The mains clearances were set at .0025, r at .0027. This builder has been in business for over 30 years so I'm not going to argue with him about where to set the clearances. Theses are fuel injected so I've checked the a/f with a FAST wideband dozens of times- mid 12's at idle, mid 11's in the 2000 rpm range where it spends very little time, and consistently in the mid 12's at 3000+ rpms. As mentioned rods and crank were factory new (Scat) but the rebuild sheet lists "checking" rods and crank. Oil pump is listed as 601-1050 but I'm not sure of the brand. They did recheck the pickup placement and it was correct, 1/2" (I think) from the bottom of the pan.

Everything to from the remote oil filter is 1/2 inch and stock Merc parts. I removed all the lines after the season and having a guy here on OSO to make me up some new ones. Have never seen pressure above 50 psi and figured it was just my gauge. Also been noticing some lower pressure late in the season, so bought a mechanical gauge to check pressure in spring

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