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Old 01-03-2009, 01:40 PM
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rod bearings premature wear

hi guys,
while i'm working on my 350 GM, i saw a little wear on the distributor gear and to well understand the problem i decide to take the cam off and check even his gear, fortunately, nothing serious, but too much i think for around 2000 miles, i need to change the cam bearings because the machine shop didn't changed them and they show a little wear ,anyway we will discuss about that later.
while tearing down rod and pistons i look at the od bearings and i see this:






there's a noticeable wear on the top fo the bearings, where the load is bigger.
the lower side as you can see in not so bad, well, the bearings have around 2000 miles on, bearings are Clevite 77 .
the engine isn't nothing special, 350 with Edelbrock performer plus cam, flat top pistons forged, the oil pump is a high volume Melling and that's what i want to talk about.
i saw many threads talking about the pros and cons of high volume pumps, now i've got premature wear on both distributor gear and cam gear and an abnormal wear in the connecting rod bearings, it's probably not related to that pump, anyway i will go with stock oil pump, but i can't understand the reason of the worn out rod bearings yet.
i took some measure of the crankshaft and seems to be ok, is 2.099, the smaller limit of the standard size, weel i thought that a too small crankshaft can cause this problem due to the load just in the higher portion of the bearing and rod obviously, this explain also why the lower portion of the bearings is in good shape.
the engine is on a Jeep so it's under 2500 rpm in mostly situation, may be too much load on the rods with not too much oil pressure? the oil pressure also is pretty high rarely goes under 30 psi when hot and usually stay around 50.

may be a poor quality oil? i personally don't think so, i've used Texaco 15w40 super ursa then Castrol magnatec 10w40 , and Texaco again when the engine smokes a lot due to the worn out valve stem seals.
i've spoked with guy at the machine shop and he told me could be a poor oiling, but i really cannot figure out where could be the issue.
i'm open to tips, any help will be apprecciated.

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Old 01-03-2009, 01:53 PM
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I see a lot of trash in the oil, probably from dirty assembly situation.
There is some direct scuffing also.

As far as the wear, that looks more like 150,000 hard miles. Nothing is in good shape, IMO.
You have a serious problem, either clearances, oil delivery, or nasty oil.
All of the above.

Off hand I would suggest that the assembler failed his test.
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Old 01-03-2009, 02:11 PM
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That kind of upper rod bearing wear is also indicative of detonation or lugging.

tom
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Old 01-03-2009, 02:18 PM
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Quote:
Originally Posted by machine shop tom
That kind of upper rod bearing wear is also indicative of detonation or lugging.

tom

thank you for the help, as detonation do you mean too much advanced? or too much compression?

and for lugging something that has clogged the oil galleries or too much load on the engine at low rpm?
thank you
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Old 01-03-2009, 03:32 PM
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this is the crank, it shows just a very little wear around the holes, there are no big scratches on it, what do you think about it? need a grind?
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Old 01-03-2009, 04:08 PM
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bearing wear

looks like debree, take a oil sample if you have the old oil,all the failure analisis pictures in the cat failure guide point to poor clean up on assembled parts, i would say crank needs a polish at the least. there are sighns of debree on the cyl wall as well. poss block not cleaned properly after machining. best final clean is soap and water in a typhoon type washer, then wash down cyl walls with oily rag, cliff
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Old 01-03-2009, 04:15 PM
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Agree with Cliff.

Also note that most people rely on the machine shop to clean all the parts.
I have even seen big name engine shops NOT clean the crankshaft passages with gun bore brushes, and some don't even clean the oil galleries.
Relying on the machine shop to hot wash every thing is dangerous.
They do the best they can, but it is NOT THEIR JOB.

That is why I said, the assembler goofed up. It was HIS responsibility to make sure everything was/is surgically clean, and every clearance precise.
Everything must be checked upon assembly.
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Old 01-03-2009, 04:19 PM
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Your initial comment about distributor gear wear being excessive at 2000 miles, tells me that it is an OIL problem.... that is if the correct material gears are installed.
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Old 01-03-2009, 04:19 PM
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yes i agree,
i want to clean everything before the assembly, how do you usually clean up the oil galleries?
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Old 01-03-2009, 04:20 PM
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Quote:
Originally Posted by jeepers creepers
yes i agree,
i want to clean everything before the assembly, how do you usually clean up the oil galleries?
Gun bore brushes, brake cleaner, hot soapy water, lots of elbow work. SCRUB everything.
Any place the gallery tubes meet at a 90* angle must be relieved of the tube plugs and cleaned thoroughly.

Cylinder walls should be sparkly clean. No color should come off the cylinder walls onto a clean white paper towel. Any color is usually microfine metal particles.

Remember, rust is gonna be visible in a few hours if you don't spray it with some rust inhibitor.
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Old 01-03-2009, 04:37 PM
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engine wear

All good ideas. Something else to look at is the possability of gas getting into the oil and thinning it down. Either with a faulty fuel pump or a flooding carb problem. Just another idea.
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Old 01-03-2009, 04:44 PM
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i thought that me too, the engine has a TBI that works really really good, no one hesitation flooding or stumble, never got a backfire once installed the throtthle body injection instead the carb.
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Old 01-03-2009, 09:37 PM
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Quote:
Originally Posted by machine shop tom
That kind of upper rod bearing wear is also indicative of detonation or lugging.

tom
Gotta agree too. One more thing though, detonation will show up just off center of the rod bearing when the loading is highest. Wear right in the middle often means off size rod bearings or improper crush, improper torque on the rod bolts. Something is pulling the big end outa round. Dirt in the engine will show up all around the bearing. It's not unusual to see the front worn more than the rear bearings. Twisting of the crank seems to be the problem.
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Old 01-04-2009, 01:33 AM
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What did the oil look like when you took it apart?? that greenish oil on the main bolts looks awfully suspicious. Possibly antifreeze in the oil?? blown or leaky head gaskets.??
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Old 01-04-2009, 02:32 AM
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bad news guys,
i found a nice amount of sand in the bottom of the oil pan it was hardened and attached to the oil pan

fortunately seem to be just there and i did no found anythig other around the block, so we probably can explain the extra wear of the bearings.
no antifreeze in the oil mine is red/pink colored.

so what you advice me right now?
cylinder wall look sufficient good but i definately need to tear the crank down and check even the main bearings, may be a grind and new bearings will work better,
i'm open to tips, thank you
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