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Old 09-15-2007, 01:04 PM
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4.3l V6 rod bearings

I was wondering if anybody has any insight into the 4.3l vortec rod bearing failures. I currently have one with bad bearings and when looking for another used engine I had noticed that there seem to be allot with bad bearings. The one I have only has 73000 miles on it, I bought it from the original owner who was a handicapped elderly woman who by no means drove it hard. The oil pressure fluctuates from none to lots. I am in the process of tearing it down seems like maybe the pickup tube comes loose? Would like to correct what causes the failure. The engine runs excellent except for the hammering sound. Doesn't smoke no oil leaks she changed oil religiously. She gave me all of the service receipts it doesn't make sense why it would fail when it appears to have been looked after really well.
Any insight is appreciated thanks

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Old 09-15-2007, 01:30 PM
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Most of the bearing failures in the 4.3 (and others) can be traced to the repair of intake manifold gasket leaks or head gasket replacement. When these operations take place, many technicians use an abrasive wheel or Scotch Brite® disc to remove gasket material. In the process of doing this, abrasives, gasket material, and metal particles are spread into the lifter valley and other areas. No matter how diligently the engine is cleaned, some of these contaminants will get into the oil supply and eventually tear up the bearings.

Look at the reciept and see if something like this has been done.

tom
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Old 09-15-2007, 01:47 PM
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"my grandma owned it and never got it over 30 miles an hour and only drove it to church on sunday"

yeah, so how often was the oil changed? Do you know that?
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Old 09-15-2007, 02:27 PM
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And who changed the oil? if it was any of the quick lube places they more than likely slapped on a new filter and pumped oil back in it that`s been run through a strainer a couple of times. Other than that thought, I agree with Tom, the gasket failures on these things were commonfold.
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Old 09-15-2007, 02:50 PM
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Quote:
Originally Posted by machine shop tom
Most of the bearing failures in the 4.3 (and others) can be traced to the repair of intake manifold gasket leaks or head gasket replacement. When these operations take place, many technicians use an abrasive wheel or Scotch Brite® disc to remove gasket material. In the process of doing this, abrasives, gasket material, and metal particles are spread into the lifter valley and other areas. No matter how diligently the engine is cleaned, some of these contaminants will get into the oil supply and eventually tear up the bearings.

Look at the reciept and see if something like this has been done.

tom
Excellent point, these time-saving tools are overused. I never use them on an assembled engine when critical areas are "opened up." This is an area of concern that has been mentioned in technical bulletins from manufacturers of HD diesel engines and no doubt from other manufacturers as well.
Like any other tool, they have their purposes, used properly. But use your head for pete's sake!
Abrasive particles flying around at high speeds are not good around your engine! This just in, film at 11:00!
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Old 09-15-2007, 03:41 PM
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Yes. I get "Scotchbrite milled" heads in all the time.. These guys jusy don't have a clue to the damage they cause..

As for 4.3 bearing damage. I was told by a bearing guy. That the reason for all the front rod and main wear is becaose GM went to the large pickup tube on the oil pump.

SBC chevies had no bearing problems since 55. Same with the 229 and many early 4.3's. All had the smaller inlet tube on the pump..

The reason, I was told, for the 4.3 problem, is when the engine is shut down. The oil naturally drains down to the pan. When the engine restarts. The extra internal volume of the large pickup tube creates a large air pocket that takes just an instant more to overcome and in that time the front rod/main bearings get starved or a weak air/oil combo from the oiling system. Causing just that little bit of wear. That plus the imbalance harmonics of this engine design really test the bearings.
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Old 09-15-2007, 08:24 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com
Yes. I get "Scotchbrite milled" heads in all the time.. These guys jusy don't have a clue to the damage they cause..

As for 4.3 bearing damage. I was told by a bearing guy. That the reason for all the front rod and main wear is becaose GM went to the large pickup tube on the oil pump.

SBC chevies had no bearing problems since 55. Same with the 229 and many early 4.3's. All had the smaller inlet tube on the pump..

The reason, I was told, for the 4.3 problem, is when the engine is shut down. The oil naturally drains down to the pan. When the engine restarts. The extra internal volume of the large pickup tube creates a large air pocket that takes just an instant more to overcome and in that time the front rod/main bearings get starved or a weak air/oil combo from the oiling system. Causing just that little bit of wear. That plus the imbalance harmonics of this engine design really test the bearings.
That's good info. I'll bet nobody makes a 5/8" pickup tube for the 4.3 chassis applications. I'll look into it......


tom
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Old 09-15-2007, 08:35 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com
I get "Scotchbrite milled" heads in all the time.. me and in that time
I apologize for the slight change in subject but I must ask anyway. We use the same scotchbrite pads for cleaning parts at work but never on machined surfaces. How do those affect gasket sealing? I have seen those scotchbrite discs put a wave in an otherwise smooth surface and really don't understand why somebody would use one on a head sealing surface.
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Old 09-15-2007, 09:22 PM
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Well I got it apart quite easily actually. Just drop the front diff and down comes the pan. It is the rear most bearing that is pooched kinda weird you would suspect it to be the front one. I agree with the 3/4" pick up tube makes sense. A small block pump looks pretty much the same I will compare the two side by side. I know melling makes a 5/8" pickup for this pan so I will change pump and pickup.
Thanks for all the help
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Old 09-16-2007, 09:52 AM
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i have done lots, and know people that have done LOTS more than me. of those intake gaskets. we all use the rol-loc disc's and scotchbright pads to clean the surfaces. we put rags down in the valley to keep junk out. we have NEVER had a problem. i guess it depends on how they are used.


this is the first i have heard about bearing problems.
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Old 02-16-2012, 02:57 PM
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I understand there is a big difference in the diameter of the rod bearings on the 4.3 vs V8 engines.

Can someone verify this ?
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Old 02-16-2012, 03:05 PM
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Quote:
Originally Posted by Vortech 4.3
this is the first i have heard about bearing problems.
Now that this thread it 5 years later, these engines naturally have more mileage on them. Also, we're (S10 forums/Blazer/Bravada type forums) seeing a much high incidence 4.3 engines knocking. Most of the engine knocking were seeing is on engines that have 125k+ miles on them.

Craigslist is loaded with 4.3 engine'd vehicles that have knocking engines! Look around.

You'll see what we are talking about.

It appears to me this is a engineering/design flaw.
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Old 02-16-2012, 04:34 PM
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Yes the rod bearings are larger on the 4.3. This was done to put more "meat" in the rod throws between the two adjacent rods on the offset pin grind. These cranks tend to be weak in this area even with the larger bearings. Very small cross section. Especially the front journal. I've seen many 4.3's ( including one of my shop trucks) break at the front journal. Usually junks the front main bore.
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