Used 360 main bearings evaluation

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65 Cuda 340

65 Cuda 340

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I'm switching from the stock oil pan and factory windage tray in my 74 Duster 360 motor, which has been in my 67 Barracuda since 1991. Not sure how many miles, probably 30-40 K.

New oil pan is Kevco, which has a built in windage tray. So I don't need my factory tray or the special main bearing bolts with the windage tray attachment built in. So, I removed the special factory main bolts and, while they were out, pulled the ## 2 and 4 main caps.

Mind you, this motor has been running fine, great oil pressure, etc. Ran 13 zeros at 106 last summer.

The only machine work done to the block back in 91 was to bore it .030. Stock rods, stock replacement cast pistons (except no dish), not square decked or align bored or honed.

The two main bearing bottom halves I have visual access to show some wear into the copper layer and one gouge that appears to have been there a long time. Otherwise smooth enough to pass the fingernail test.

I see nothing on the crank itself.

Long range plan is to build a 416 out of the motor. But right now, I am just putting a hotter cam in it and replacing the oil pan.

I think these bearings are OK to continue using, but thought I would see what you guys think. Here they are:

1754771598711.jpeg


1754771624470.jpeg
 
mgoblue9798 said:
If you had good oil pressure before the teardown I would run them.
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That wear is only going to get worse, we don't know what the other half of the bearings look like. I think that it's cheap insurance to change them now while he already has it apart. Good oil pressure in the past doesn't mean he'll have good oil pressure later on.
 
I'm a believer in Murphy's law, if something can go wrong it will. I'd rather be safe than sorry.
 
Dan the man said:
That wear is only going to get worse, we don't know what the other half of the bearings look like. I think that it's cheap insurance to change them now while he already has it apart. Good oil pressure in the past doesn't mean he'll have good oil pressure later on.
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Everyone has an opinion, I gave mine.
 
Do you have access to a bearing mic? (I think technically it's called a round anvil mic, but I always heard them referred to as a bearing mic or tubing mic.)

You can measure the bearing thickness at various locations. It would give you some peace of mind if you had the numbers.

1754774702316.png
 
Kuz said:
Do you have access to a bearing mic? (I think technically it's called a round anvil mic, but I always heard them referred to as a bearing mic or tubing mic.)

You can measure the bearing thickness at various locations. It would give you some peace of mind if you had the numbers.

View attachment 1716440023
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That's a good idea. My question is what about the copper that is already showing, could that cause or have caused main bearing journal wear? Also, we don't know what the top half of the bearings look like. I realize that we all have a different opinion and that's good and I agree on that.
 
I checked one rod bearing. No copper showing.

They would be relatively easy to replace. The main bearings, no. The engine is still in the car.
 
If you won't have the motor forever, don't let the magic out. Most cars on the road have worse looking bearings. Pretend you didn't see anything. It. Will. Be. Fine.
 
Stick some platigauge in there and get the clearance. If it’s excessive, replace em. If it’s not, SEND IT!
The copper showing is not a reason to replace a bearing. Excessive clearance is.
 
Are they #2/4 ? If so the oil is not turning to the bearing from the main oil gallery ,oil speed is too fast.You would be turning it to many rpm and should do the oil mods to block ,but if all bearings look like that its wore out.
 
TT5.9mag said:
Stick some platigauge in there and get the clearance. If it’s excessive, replace em. If it’s not, SEND IT!
The copper showing is not a reason to replace a bearing. Excessive clearance is.
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I have a question about this, isn't copper showing a sign of excessive wear
 
Dan the man said:
I have a question about this, isn't copper showing a sign of excessive wear
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instead of typing out a long winded response which you'd ignore the premise of and then reply by posting two responses, one right after the other, one contradicting the other i'll keep it succinct:

it depends...
 
@Dan the man instead of us giving you the answers, do a little research on the different layers of engines bearings and what they do. Come back and let us know what you learned.
 
RustyRatRod said:
I don't like the looks of the bearing on the left in the second picture. That's a worn groove next to the oil groove.
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I thought the same thing but the OP said they pass the fingernail test so it has to look worse in pictures.
 
Kuz said:
Do you have access to a bearing mic? (I think technically it's called a round anvil mic, but I always heard them referred to as a bearing mic or tubing mic.)

You can measure the bearing thickness at various locations. It would give you some peace of mind if you had the numbers.

View attachment 1716440023
Click to expand...
Excellent response.
 
TT5.9mag said:
@Dan the man instead of us giving you the answers, do a little research on the different layers of engines bearings and what they do. Come back and let us know what you learned.
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I'll do that. I already did some research for my own piece of mind and I'm going to do some more
 
RustyRatRod said:
I don't like the looks of the bearing on the left in the second picture. That's a worn groove next to the oil groove.
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yea there's been some foreign matter floating around, typical for a used engine.
Me, I'd replace them because I'm there and bearings are cheap, wouldn't waste my time gauging them.
 
TT5.9mag said:
I thought the same thing but the OP said they pass the fingernail test so it has to look worse in pictures.
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I didn't express myself very well, but I meant that it passed the fingernail test except for the groove. Something must have got between the crank and the bearing at some point. But I see no visible crank damage in that area from whatever that was. I'm kinda thinking it's been there for a while, not sure what could possibly happened recently to make that groove.

Of course, I suppose I should rotate the crank to make sure that main is OK all the way around.

As for replacing the bearing, I would for sure if the motor was apart, but other than the cam related stuff up top, the motor is together except for those two main caps. Since it was running well, I tend to think it would be OK to run as is, especially since I'm not sure how I would replace the upper shell with the crank in place. I've read that it can be done, but I've never done it. On the other hand, I really don't like the looks of the groove.

I won't do much one way or the other until Monday. Did yard work all afternoon - mowing three acres and significant tree trimming. Even with my grandson's help, that was a big job and we're both tired. And we are having family over for more yard work and a big dinner tomorrow.

I appreciate all the contributions so far. A lot for me to think about, and I think I'm changing my mind as we go along.
 

RustyRatRod said:
I don't like the looks of the bearing on the left in the second picture. That's a worn groove next to the oil groove.
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That does look like a groove, it could also be the shading creating that illusion.

If it were my engine knowing oil pressure was fine and those bearings passed the finger nail test, I'd just send it. I could just be lazy and avoid FAFO sometimes.

Edit:
I replied late, OP said it was a groove, that confirms the suspicion.
 
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65 Cuda 340 said:
I didn't express myself very well, but I meant that it passed the fingernail test except for the groove. Something must have got between the crank and the bearing at some point. But I see no visible crank damage in that area from whatever that was. I'm kinda thinking it's been there for a while, not sure what could possibly happened recently to make that groove.

Of course, I suppose I should rotate the crank to make sure that main is OK all the way around.

As for replacing the bearing, I would for sure if the motor was apart, but other than the cam related stuff up top, the motor is together except for those two main caps. Since it was running well, I tend to think it would be OK to run as is, especially since I'm not sure how I would replace the upper shell with the crank in place. I've read that it can be done, but I've never done it. On the other hand, I really don't like the looks of the groove.

I won't do much one way or the other until Monday. Did yard work all afternoon - mowing three acres and significant tree trimming. Even with my grandson's help, that was a big job and we're both tired. And we are having family over for more yard work and a big dinner tomorrow.

I appreciate all the contributions so far. A lot for me to think about, and I think I'm changing my mind as we go along.
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The trash that goes through bearings usually happens very early in the engines life. Like the first 10 minutes of break in. That’s probably when it happened. I’ve rolled hundereds of upper bearing shells in race engines at the track with the crank in place. It’s pretty easy, use a small pick and push the old one out while rolling the crank, and roll the new ones in. My opinion is still the same though, get some plastigauge and check the clearance, if it’s within spec, run it.
 
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