New engine has a bad main bearing

C Body Bob

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Ok I bought a 440 engine from a fellow racer for FURYIOUS. He had just bought the car with the intention of putting a stroker motor in so he sold me the engine out of the car. I’ve seen it run & have videos. 60 psi at idle. No smoke or noises. So today I decided to check the bearings. A couple of the rod bearings toward the back showed a small amount of were. Crank journals looked good except one had some scratching but not an issue. When I pulled the mains they all looked very good except #4. It looks like trash possibly from the oil galley cut into the bearing. Crank journal looks very good. My question is can I just replace this one bearing & install
AC698B58-331D-4348-875C-B785159B6F76.jpeg
the engine or should I have the crank checked which would require a full tear down. Which is what I trying not to do. Really not sure at this point
 

Owen11x

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You can try the scott bright clean up and polish crank then reinstall bearing but the picture looks like rough id be affraid ot may spin it
 

70bigblockdodge

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Measure crank with a set of vernier calipers and R&R bearings with right size. The bearing looks like it did exactly what it is supposed to do, absorb debris and load without hurting journal.
King engine bearings if you want a brand suggestion.
 

413

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If the journal looks good then replace the bearing and go. Measure the journal first to be sure. Also measure the rod and main bearing clearances so you know what you’ve got in there, and what weight oil to run.
 

Davea Lux

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Unless you have a bunch of extra bearings laying around, you will probably need to buy a full set, so replace them all. As noted mic the crank and have it polished if needed. The oil pump gears may also have impacted debris, so check them carefully. Also note that those debris are an indications of parts failing someplace else in the engine, the cause should be determined.

Dave
 

C Body Bob

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Unless you have a bunch of extra bearings laying around, you will probably need to buy a full set, so replace them all. As noted mic the crank and have it polished if needed. The oil pump gears may also have impacted debris, so check them carefully. Also note that those debris are an indications of parts failing someplace else in the engine, the cause should be determined.

Dave
I didn’t get the oiling system with the engine. He has a chassis car & used a flat bottom dragster pan & a Milodon oiling system. He needs to keep that with his car. I agree something got to that #4 main.
 

C Body Bob

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If the journal looks good then replace the bearing and go. Measure the journal first to be sure. Also measure the rod and main bearing clearances so you know what you’ve got in there, and what weight oil to run.
Yea the journal looks fine. All the bearings looked good besides #4. May just put a bearing on it & button it up.
 

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Yea the journal looks fine. All the bearings looked good besides #4. May just put a bearing on it & button it up.
Agree, but if was racing this I would want to know what the bearing clearance is. Yes debris did this not a clearance problem.
 

C Body Bob

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Agree, but if was racing this I would want to know what the bearing clearance is. Yes debris did this not a clearance problem.
I can check that with plastigauge. The motor is suppose to be fresh. Pistons look new, nice crosshatch on cylinder walls.
 

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Ideally you would take the crank out, polish it and measure it, and double check for debris in the oil passages. However if you don't see any other issues and the journal doesn't have any raised flaw issues upon close in-place inspection, you may be able to get away with just a single bearing swap. I may have a new single bearing I could set you up with, depending on size. I believe I still have some, particularly std, left over from when I used to race.
 

MONC440

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That looks like some kind of debris, not clearance issue. Are the oil passages in the crank chamfered? If not I have had a rough edge on the crank oil passage cause bearing damage. If it were me I would completely disassemble the engine and check all oil passages in the block and crank for more debris. Be sure to check the oil passages between the crank and camshaft bearings. I had an engine once that one cam bearing was installed just a bit off and caused bearing failure. If you don't find anything then put it back together and plastigauge as you build. Just my $.02
 
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413

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The one piece that damaged that bearing is probably imbedded in the bearing. The oil passages are clean because no other bearing is damaged. Replace bearing and go.

A machining defect didn’t do this damage.

Agree don’t use scotchbrite inside and engine that’s going together. Talk about debris running through it.

The title line is wrong, it’s a damaged bearing, not a bad bearing. An engine could run for years with this bearing looking like this and you would never know it.
 

C Body Bob

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Guys I’ve read all the comments on here & Facebook. A couple conversations with my crew chief. 35 years building & racing MOPARS. Called my friend the guy I bought the engine from. He came over & had a look. Also 35 years experience racing MOPARS. My shop helper had a look. 45 years as a professional mechanic. We have all come to an agreement. Install a new main & one rod bearing. Plasti gauge both. If it specs out. Torque it down & send it. My friend even gave me $50 bucks for the two bearings. So that’s the decision we collectively have made.
 
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