Be Warned - 3100 Failure

[sprucegagt]

So the stock cam bearings are not the same width as the cam journals? I ask because I haven't pulled my engine to know for myself.

[gpse3400]

I think there is too much over analyzation here. The engine was old, thats good enough for me. How it failed it irrelevant. For the record I have seen a 2.8W Go well past 330K and still ran just fine....of course I'm sure it wanted to be put out to pasture.

A 3400/3500 would be a much eaiser swap.... 3500 with some parts from WOT Tech....

[lkurek]

Really? Overanalyzing? I guess to some people, but I wanted to get this out there as a data point for others facing similiar situations. Frankly, this is NOT the first time I have heard of trashed cam bearings in these engines causing problems. In all my years, that is VERY rare.....especially with stock spring pressures. I would think an old motor would WEAR out, not catastrophically fail. I don't mind getting a lot of mileage out of an engine, and then it gets weak over time and you replace/rebuild it. Snapping a cam in half.....on a well maintained engine.....is not acceptable ever.

That being said.....

The point on the 3400/3500 is moot.... First, it shares a common design with the 3100, so I would assume there is still the issue with the cam bearings. Second, I already dropped a 3.4 DOHC in, and am in the process of debugging it. I like that motor a LOT more than the plain old pushrod ones

Larry

[3100 MPFI]

are you the original owner of the car?

[lkurek]

Hmmmm.....original as in bought from dealer, no. I bought it with about 90K on the clock, so I have owned it for over two thirds of its life.

I was/am his adopted father....and I raised him

[Rhedalert]

Hmmmm.....original as in bought from dealer, no. I bought it with about 90K on the clock, so I have owned it for over two thirds of its life.

I was/am his adopted father....and I raised him

I bought my '95 Cutlass with 93k on the clock, and the LIM gaskets were already done. Did the LIM gaskets look original when you replaced them?

[1meanz]

my uncles lumina did the exact same thing. it had NEVER had a bad lim gasket, and yes, he had changed it. he owned the car since new so it couldnt have happened befor he got it. had about 180 or 190k on it. was driving down the road and it snapped. the only 2 things we found is that 2 of the roller lifters were gone, the rollers were flattened out in about 3 places. and all the cam bearings but one came out like spageti. they litterly came out in little shreds. we still cant figure out what caused it. but it was NASTY!

[IanSzgatti]

I have owned it for over two thirds of its life.
I was/am his adopted father....and I raised him

wow...thats noble... and I completely agree, parents shouldnt outlive they're fucking camshafts...

[gpse3400]

Really? Overanalyzing? I guess to some people, but I wanted to get this out there as a data point for others facing similiar situations. Frankly, this is NOT the first time I have heard of trashed cam bearings in these engines causing problems. In all my years, that is VERY rare.....especially with stock spring pressures. I would think an old motor would WEAR out, not catastrophically fail. I don't mind getting a lot of mileage out of an engine, and then it gets weak over time and you replace/rebuild it. Snapping a cam in half.....on a well maintained engine.....is not acceptable ever.

That being said.....

The point on the 3400/3500 is moot.... First, it shares a common design with the 3100, so I would assume there is still the issue with the cam bearings. Second, I already dropped a 3.4 DOHC in, and am in the process of debugging it. I like that motor a LOT more than the plain old pushrod ones

Larry

Yeah I don't know about that. Old high milage engines can and do fail abruptly. When engines fail before 100K thats when you need to to start figuring out why. Anything else after that is typically known(at least around here) that the powertrain can potentially fail. And not for nothing those GEN3 lower intake gaskets cause alot of problems, esspecially when you think nothing is wrong. I think Felpro has finally solved the problem.... You dont have any control on how and when an engine fails at that mileage even if it was well maintained. If it gets past 100K the design is pretty sound.

[CobraCDR]

OMG dude the engine hade 285k on it not 28.5k give it a break. The cam snapped big woop common that is almost 200% more than the life span of that engine. From a design standpoint that is phenominal. Be grateful it made it long. WTF is wrong wit you guys? Unbelievable you guys ever heard of friction and wear before? Or do you have magnetically suspended bearings in your engines which have almost no friction? Oh right these are journal bearings which are like the cheepest and most prone to wear of any bearing type...I mean it is not high technolgy we dealing with here. The only bearing that is there is the oil and that wears out so you are left with metal on metal and after time its going to seize and what do you think is going to happen? Is the cam going to stop the combustion process? The entire moment of the engine is going to stop for the cam bearing? No the cam will and did fail. No mystery here.

Ken

PS-I think you hold the record for the highest mileage gen3 out there.

[lkurek]

Ken, Ken, Ken.....

I assume you never read the original posts I made on this subject. I am NOT complaining that I got 285K miles out of the engine, I am more upset about HOW it failed. Seriously.....if you cannot distinguish between and engine WEARING out and a part catastrophically failing, then I don't know what to say. I fully expect an engine to wear out. Hell, it isn't going to last forever. The problem I have, is that there seems to be a common problem with these engines munching cam bearings at higher mileage. Do YOU think snapping a cam (remember, we are talking a stock engine with stock springs staying at low/med RPM) is acceptable? Do you think munched cam bearings are normal? I have literally rebuilt, no joke, 20-25 engines in my life, and I have NEVER seen one eat cam bearings. Ever. This was my first higher mileage V6-60, and from what I found talking to other guys.....they have similiar problems.

Design flaws, especially those that are NOT fixed (LIM gasket, apparently bad cam bearings, etc) are still flaws....regardless of the engine life.

Just another point of reference..... As I pulled the engine apart for a post mortem, EVERY other area of the engine, from the valve guides, to the rod/main bearings, to the crank, to even the timing chain were as good as new. Seriously. I mic'd everything and all of it was barely off of new....well within the acceptable specs for a NEW engine, nevermind one that has 285K on it. Go Mobil1!!!

[gpse3400]

...20-25 engines is a small scope on the X-amount of engines in the world. Just because it happens to you in you part of the world doesnt mean it happens to anyone else. Other things wear out faster than others. You push the milage past 100K, 150K 200K, you going to test out the part's ability to last. It is sad but it is irrelavant how it fails at those milage points esspecially if you are not the original owner that conducts all the maintenance. The factory only cares if the engine will make it to 30k, 60k or now these days 100K. Anything else after than is a bonus. A proper course in mechanical theory will take all the surprises out of your "autopsy".




FYI the TDC is far from indestructable. So other than you "liking" it, changing to it to avoid this "cam bearing" problem is errored reasoning. You still have the same cam bearings and blank in the block to run the oil pump and the 2nd phase timing system so there is plenty of load on all of that. More often than not they will spin a rod bearing or if you have standard shift wear the thrust bearing.

[lkurek]

OK.....granted, in the world of automotive production, 25 engines is a small number. I'll give you that... However, for ONE person, who is an individual and not a shop.....that's a lot, no? I'm just trying to say I am not a novice when it comes to tearing apart old engines.... And as for your comment about taking a "proper course in mechanical theory", I'd like to say a lot....but I won't. I don't need a flame war here, but frankly, I have taken classes in FEA and NDT. I have performed the QA function for a nuclear project at one of the DOE national laboratories. So, Mr Smarty Pants.....I do know a lot about mechanical and material theory.

Can you not agree that there is a POSSIBLE design flaw in teh cam bearings/oiling/whatever in these engines? I'm throwing out a data point.....as a service, and you get on my ass? Thanks....

As for WHY I went with the DOHC.....you must be joking. Just to avoid camshaft failure? That's too funny! There are WAY more things that can go wrong with this engine than a standard cam in block pushrod motor. If ease of maintenance, reliability, low service intervals, etc were what I was looking for, I would not have gone with this motor. Just to clarify....the reason I *did* go with it, is that it was a stock engine in the uplevel version of the car. That meant there were lots of factory parts and pieces that would be available to do this right. I didn't want to kludge a bunch of late model stuff (ie 3900, 3500, etc) into this car, because to do it RIGHT would mean a lot more upgraded parts (cluster, BCM, etc, etc). I put this engine in because a)I had one available, b)it came stock in the car/year, c)it's a challenge, and d)it should be more reliable and 100% functional than dropping say a later L67 in.

Sigh......I guess no good deed ever goes unpunished or second guessed, right?

[CobraCDR]

Agreed the cam snapping is not normal but I doubt the "cam design" is at fault here. More likely deathcool took out the LIM multiple times in this engine's lifespan contributing to the cam bearing failure mode and the ultimate seize of the cam and the torsional failure. It is no question that the hollow cam when compared to a solid cam of the same OD has a weaker critical strength (if we were to increase the od of the hollow cam it would be a different story) but all things equal it is weaker. This may be why the gen II's don't snap when they seize up the cam or whatever. Just for reference my Gen 2 3.1 in my garage has totally shot cam bearings way out of spec. and all scratched up to hell and back.

Please post up pictures of the cross section of the failed components, both of them. If you looked at the metal grain in the area of failure you will be able to tell if it was a torsional failure or bending mode failure. Get us pictures of the cam both halves in the failed area (close up shots) and the cam bearing nearest the failure.

Remember everything man made is prone to failure some more than others. This is the first snapped gen 3 cam I have ever heard of. This does not sound like a problem that is rampant with the 3rd gen 60 degree

Ken

PS-If we are flashing credentials here I have a BSME from Rensselaer Polytechnic Institute I have held positions in both design and manufacturing of roller bearings, Heim joints (Actually worked at Heim bearings) and turbine main bearings. I currently work for GE aviation designing high temperature thermocouples for commercial gas turbine engines air, land and sea based. I conduct FEA analyses on a daily basis including thermal, static, dynamic and fatigue. I have participated in multiple field failure investigations involving the FAA, BELL/Boeing and the US military. I have successfully redesigned dynamic pressure switches based on these investigations to satisfy both the customer requirements and the military aircraft environment (V-22 Osprey). Shall I list more?

[lkurek]

Oh, it was definately a bending failure, not torsional. The cam was NOT seized up in the bearings, but a) the bearings (two middle ones) were worn abnormally (ie paper thin, scratched up, etc.) The two end bearings were actually in good shape. Sooo.....as I see it, the cam has been flexing (due to the lack of support in the middle)and it snapped similiar to taking a paperclip and bending it back and forth until it snaps. I'll see about getting some pics posted.....but it won't be until tonight.

As for the LIM gasket.....no, it was not trashed, but was close. The plastic carrier that holds the actual seal was cracked, and it was only a matter of time until it broke. There was no coolant in the valley, none in the oil, and it wasn't leaking when it ran. The lifters were in perfect condition as well.....as were all the lobes.

I'm chalking this up as the primary failure being the cam bearing, and the actual snapped cam as the secondary (and fatal) failure.....which for a cam is kind of an unusual way to go.

Oh, FWIW, I never replaced the LIM gasket and whoever owned it before me didn't either.....as it was the factory gasket. I *did* over the life of the motor periodically make sure the LIM bolts were torqued to spec....whcih may or may not have helped. I also did NOT run Dexcool......hate the stuff. Always ran the good old Ethylene Glycol In 95, factory fill was the green stuff too.....

BTW....nice cred's there Your company is taking a pounding today, my condolences. I see your division though pulled it out .....? I seriously wish, looking back on it, that I went into mechanical engineering, as I wanted to do, rather than Finance (which at the time, looked more lucrative).....sigh.......