What is with Rod Bearings dying?

[Import Power]

Originally Posted by 92stealth15g

Was the engine broken in properly? I have heard if you hot rod within the first few hundred miles of a rebuild you will have problems and spin bearings real quickly.

Rod bearings and breaking in an engine have nothing to do with each other. A rod bearing does not break in. It has no idea if you have 1 or 10,000 miles on the engine (sans the extra wear it will have).

The only part in the engine that needs to be "broken in" on a fresh engine are the rings. Once they are seated it is broken in and can be pushed as hard as you wish {given the builds ability and tuning}

Personally I break in engines hard and have never had a ring seat issue.
But that is controversial.

Rod bearings fail for many reasons.
Oil contamination
Lack of oil/heat
Detonation
Improper engine build (replacing bearings on a spun journal without getting journal fixed, improper turning of crank after spinning bearing and other bad building techniques such as improper specs, non use of assembly lube etc)

[Patryn]

I would venture to say the car saw nothing over 4k rpm or 6 psi in the first 2500 miles. Broken in yes, but back to the bearings, you see we have strengthened rods, pistons, etc, but bearings is there a way to strengthen them, is there a custom brand out there that can be used. I've have about 4 of these cars myself, and my entire time working on my own and others, I've never seen a broken or warped piston or rod, its always the freakin bearings. I'm really looking into the grooms shortblock as it comes with a lifetime warranty. And they do something with the oil passages in the engine as well to help out with the oiling issues our engines have. Just need more info on exactly what they do and if it does what it is supposed to do.

[Import Power]

Personally these are my opinions. Take them for what they are worth. Others may have their own.

It's not the bearings. They are not failing due to the construction/material. It's the size of the bearings. Look at DSM rod bearings. Look at the 3.5L rod bearings. The 6G72's biggest weak point imo is the small size of the bearing. Smaller size means less area for load bearing. Throw in FI and it only gets worse.

Now, on T4, we have never spun a bearing, or even pounded one flat {rod or main}. This past season we haven't even seen wear on mains or rods enough to show appreciable copper.
Now, this may be due to using new OEM crank, oil pump, perfectly spec'd build using clevitte bearings with plenty assembly lube. Proper pre lube before startups, good tune etc. But bearings just are not an issue on T4 and she arguably is one of the most powerful 3S's here, and probably the most powerful bar none 3.0-3.1 here. So it's not power that is killing bearings.

Maybe, and this is total conjecture on my part, the use of certain rods and pistons take a certain amount of shock away from the bearing load? Not sure.

[JasonY]

Dont you guys have Pauter rods in T4? They are pretty much the heaviest rod on the market for our cars arent they?

I attribute most engine failures to poor builds, even a decent build will last a little while, but if its not perfect, eventually it will go. Be it 5k miles or 20k miles it will eventually let go.

Jason

[Patryn]

So in essence a lighter weight piston and rod combo take some stress off the rod bearings? Do any of you guys have any knowledge of the grooms engines for our cars?

[speedy25]

Lots of opinions and theories but there should be a REAL reason for this, but yet no-one has come up with one.

Initial failure cant be blamed on debris, and could be when it happened a second time, but all the posts I've seen claim to have flushed engine components thoroughly.

THEN there is the fact that all the bottom end components are very robust.

I put my NA motor back together with used parts and new bearings and it works wonderfully and I'm well past the typical 5k re-blowup time. BTW- My motor failed from some goober who didnt understand that rod bolts needed to be torqued. I found the missing nut AND rob bolt un-damaged in the pan!

Recently I was talking to a motorcycle racer friend about a bike that had a penchant for trashing rods and heads and he revealed that the motors were bolted into the frame in a stressed condition. (frame and motor dimensions werent the same and fasteners clamped them together!) When the motor mount points were shimmed the problems went away. Any chance of a connection that way that some stress on the blocks from movement (or lack of it on solid mounts) may be the culprit. Others have also blamed replacement crank pulleys without rubber damping as causing harmonics to destroy engines yet there are many that have many miles on them with no problem.

Is it time to create a database of failures to learn whats really going on? WE have learned to obey the 60k/120k routine to make sure timing components dont fail. Maybe there is something to be learned here for the survival of rod bearings.

-SP

[MustGoFaster]

Originally Posted by JasonY

Dont you guys have Pauter rods in T4? They are pretty much the heaviest rod on the market for our cars arent they?

I attribute most engine failures to poor builds, even a decent build will last a little while, but if its not perfect, eventually it will go. Be it 5k miles or 20k miles it will eventually let go.

Jason

Pauters are lighter than stock, and about the same weight as the 3SX H-beams. I can't find any info on other rod's weights. PAUTERS ARE NOT "HEAVY PIGS" LIKE SOME PEOPLE MAKE THEM OUT TO BE. I have no idea why that gets me so much but it does. If I ever have my hands on any other rods they will hit the scale.


Patryn- what grade of oil are you using? Did you REPLACE the oil cooler? Do you allow the car ample time to warm up before you run it hard? It takes oil a bit longer to reach operating temp than coolant.

I'm with IPO on the break in, rings are the only thing you break in. Everything else in theory never touches so how can it break in?

[JasonY]

Thanks for correcting me, just another thing ive heard so many times on here

FWIW: i had pauters in my last car.

Jason

Originally Posted by MustGoFaster

Pauters are lighter than stock, and about the same weight as the 3SX H-beams. I can't find any info on other rod's weights. PAUTERS ARE NOT "HEAVY PIGS" LIKE SOME PEOPLE MAKE THEM OUT TO BE. I have no idea why that gets me so much but it does. If I ever have my hands on any other rods they will hit the scale.

[ruben2566]

I know this is going against what others have said on this forum for years, but the rod bearing failures still don't go away. Rod bearing failure in these engines have nothing to do with the rod, bearing, or the quality of the build. It's not a clearance problem, out of round journal, finish of the journal, oil pump that keeps being changed without results. These engines have alot of oil in suspension. 24 oil squirters for the rockers, 10 cam journals, 12 piston oilers, mains, and the last in the chain to be oiled the rods, so their the first to starve for oil. If there were a problem with the build you would know it immediatly. I had 120,000 miles on my motor before it spun #3 rod bearing, so that wasn't caused by a build problem. The engine starved for oil. I have modified several FL3S members oil pans to add 1 1/2 qts of capacity to the stock oil pan. I have 20,000 miles on my build since rebuilding the engine without any problems. Going to a thicker oil makes the problem worse, it takes longer to return to the sump. I offered this service for $250 dollars, most thought it would be cheaper to take their chances. Some people have spun bearings on more than one engine, because they have'nt changed their approach to the problem. If you have a new bottom end with tight clearances,you shouldn't use an oil thicker than 10w30, even thinner would be better. Another thing that has been missed is that the oil is also used as a coolant to carry away the heat. If the oil is too thick, enough won't flow to keep the parts separated and cool. You will have high oil press, but it's not going where needed, just recirculating in the pump.

[Stealth 222]

Originally Posted by Patryn

Yeah, the oil pump was replaced, oil cooler and turbos flushed, to get rid of any bearing material. Oil pressure has always been good usually 20-25psi at idle and upwards of 50-70 during cruise. I installed an electronic oil pressure guage to do away with the crap stocker. I don't know what the pressure was, because it developed a slight knock while it was being dyno tuned.

Is there a bullet proof bearing out there, clevites go just as well as stockers.

Flushing the oil cooler doesn't seem like good insurance if your trying too prevent another spun bearing. Hot oil flowing through it at 50+psi would probably work anything lose that was left behind when it was flushed.