Spun 360 Rod Bearing

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SpeedThrills

SpeedThrills

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I bought a used 360 w/ balanced stock rods and crank, KB191's (measured 10.9:1), 292* .508 purple cam, and ported 915's w/ 2.02 intakes. It has run mostly 11.90's in a 3000# (at the line) Duster.
I took it apart to see what was in it, and check it out when I bought it, because the guy I bought it from didn't know much about it. Everything measured good.

I put new bearings and rings in it while it was apart. (I ran a stone-type hone with Scotch Brite covering the stones through it.)

Anyhow, I put about 500 street miles and 18 1/4 mile runs on it, when I started hearing a knock at low rpms, and light load. Nothing at idle, nothing at WOT. Hoping it was a detonation issue, I retarded the timing, no difference. I cut open the oil filter and found some bearing material.

Pulled it out, and just finished looking it over. No other metal anywhere. All the other bearings look fine. The filter worked! But... number 8 rod has spun the bearing. (The oil pressure was always good, 50-75 psi.)
I'm not really experienced at engine diagnosis, but it doesn't seem too bad. The only bearing material missing is the tangs.

My assembly notes say that the crank is .010" undersize. Standard is 2.125, mine (on a good journal is 2.115, the spun journal is 2.114.

My questions:
-Is this something that can be polished to fit a .001 or .002 oversized bearing? (That's probably dependent on the machine shop's inspection?)
-Should they all be polished to suit same size bearings?

Oh, and I know the cause. A bit embarrassing. My assembly notes also mention questionable crush on the cap bearing insert. I guess I erroneously figured that, "It must've been that way before, so it should be okay now".
:BangHead:

I don't have any experience with the nearest machine shop. I'm going to stop by my DD mechanic's shop and ask him about them.

I was expecting the worst (ruined crank, total tear down, etc.), but maybe I got lucky. Maybe they can polish it up, resize the rod and send it. I really don't need to sink a bunch of cash into it.
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Get high quality steel shell aluminum bearings. We use King Bearings. heat treated they look blued. The locks are stronger and they don't squash the centers out as easy from timing being advanced to far or High boost up to 60 psi. I'll bet they are loose in the rod. I have seen bearings you can spread with your fingers or when stepped on. A good bearing will go through a rubber sole of a shoe. Junk bearing you will flatten out.
 
Oldmanmopar said:
Get high quality steel shell aluminum bearings. We use King Bearings. heat treated they look blued. The locks are stronger and they don't squash the centers out as easy from timing being advanced to far or High boost up to 60 psi. I'll bet they are loose in the rod. I have seen bearings you can spread with your fingers or when stepped on. A good bearing will go through a rubber sole of a shoe. Junk bearing you will flatten out.
Click to expand...
Hi Steve. I hoped that fire isn't affecting you.
I hear you on the Kings. The bearings in it are Clevite 77's. Would you happen to know if they're comparable? I just did a little searching about bearings; there's a bunch to learn!
I'm curious as to what the machine shop has to say. I would use your son, if it weren't so far. I still might if I don't hear what I want to hear!
mygasser said:
you should get the rod resized before reassembly too, now the bearings have been spinning in it.
Click to expand...
On my list, as mentioned in the last sentence. I have to check all of them.
 
SpeedThrills said:
Hi Steve. I hoped that fire isn't affecting you.
I hear you on the Kings. The bearings in it are Clevite 77's. Would you happen to know if they're comparable? I just did a little searching about bearings; there's a bunch to learn!
I'm curious as to what the machine shop has to say. I would use your son, if it weren't so far. I still might if I don't hear what I want to hear!

On my list, as mentioned in the last sentence. I have to check all of them.
Click to expand...


You didn’t lose a bearing because the bearing failed.

You need to measure the housing bore of the rod and see where it’s at.

Measure measure measure.
 
Just had one come here from south Jersey. Make sure the shop you take it to thoroughly cleans the block and crank. He does recondition rods also. You can have it neutral balanced so any damper or torque converter can be used. We have dampers and can cut the weights off the converter. A good balance engine spins like an electric motor . The better the balance the les wear it has. We have 340 blocks cranks and rods. here also
 
man, with what that damage looks like on the cap i'd be worried about it taking a ride on the carousel again with anything short of a cut on the crank and a resize/new rod.

i guess measure it and see, but my magic 8 ball says: outlook not so good
 
Turn the crank and recondition or replace the rods. I wonder if there are others that aren't happy.
 
What was the bearing clearance when you stuck bearings in it early on?
 
Newbomb Turk said:
You didn’t lose a bearing because the bearing failed.

You need to measure the housing bore of the rod and see where it’s at.

Measure measure measure.
Click to expand...
A measuring we will go.
Oldmanmopar said:
Just had one come here from south Jersey. Make sure the shop you take it to thoroughly cleans the block and crank. He does recondition rods also. You can have it neutral balanced so any damper or torque converter can be used. We have dampers and can cut the weights off the converter. A good balance engine spins like an electric motor . The better the balance the les wear it has. We have 340 blocks cranks and rods. here also
Click to expand...
I'll be doing the cleaning. That's one aspect I'm familiar with. I'm hoping the crank I have now can be saved. Looks worse in the picture than it is, I think.

TT5.9mag said:
What was the bearing clearance when you stuck bearings in it early on?
Click to expand...
.002"

I'll get back when I have more info.
Thanks everyone for getting me going in the right direction.
 
SpeedThrills said:
A measuring we will go.

I'll be doing the cleaning. That's one aspect I'm familiar with. I'm hoping the crank I have now can be saved. Looks worse in the picture than it is, I think.


.002"

I'll get back when I have more info.
Thanks everyone for getting me going in the right direction.
Click to expand...


Did you measure that clearance with a micrometer and bore gauge or did you use plastigauge? Both work but one is more accurate than the other.

Also, I can’t think of a time when bearings were as inconsistent as they are now.

To get my mains where they should be it took two sets of bearings.

Also, did you measure that .002 on that rod and throw? When the clearance is getting under .001/per inch of shaft diameter you need to stay away from any grade of oil with a higher grade than 30.

You just don’t need it.
 
Newbomb Turk said:
Did you measure that clearance with a micrometer and bore gauge or did you use plastigauge? Both work but one is more accurate than the other.

Also, I can’t think of a time when bearings were as inconsistent as they are now.

To get my mains where they should be it took two sets of bearings.

Also, did you measure that .002 on that rod and throw? When the clearance is getting under .001/per inch of shaft diameter you need to stay away from any grade of oil with a higher grade than 30.

You just don’t need it.
Click to expand...
I used Plastigage. I can see it not being as accurate as a mic and a bore gage. I used the latter on the cylinders and pistons. I'll have to see if I can cover 2-3 with it. (Excuse the italics, I have no idea what button I hit.)
Thanks for the heads up on bearings.
Yes, that rod was .002 when I put it together. (They all were, for that matter.)
I've been using synthetic 10W30 (I used dino to break in the rings), with Rislone zinc additive, even though the cam was already broken in. I saw a video that contradicts its use, however. Somewhere here: The Motor Oil Geek I did have a film on the bottom of the pan, which I believe he mentions as being no good. I've heard good things about Valvoline Racing Oil. I'm thinking of trying it. I like synthetic, but this zinc thing is confusing. Too little, no good. Too much, no good, etc.
 
Another possibility is that the #8 rod got 'trapped'....by #7 rod. #7 rod might be bent, or has been closed & honed in the last re-build & the machining left the rod at angle. The bent #7 forces the #8 rod against the crank cheek. The oil to #8 rod is now unable to exit the brg, quickly overheats, breaks down &...brg failure.

To prevent this happening, I grind 3 oil reliefs in the rod. One at 12 oclock, one at 10 to 2 & one at 10 to ten, these last two in the bolt column. These 3 areas are the strongest part of the rod. I make the relief about 1/4" wide, 0.030" deep. If a rod is now forced against the crank cheek by it's neighbour, the oil can exit & fresh oil can enter the brg.
 
Bewy said:
Another possibility is that the #8 rod got 'trapped'....by #7 rod. #7 rod might be bent, or has been closed & honed in the last re-build & the machining left the rod at angle. The bent #7 forces the #8 rod against the crank cheek. The oil to #8 rod is now unable to exit the brg, quickly overheats, breaks down &...brg failure.

To prevent this happening, I grind 3 oil reliefs in the rod. One at 12 oclock, one at 10 to 2 & one at 10 to ten, these last two in the bolt column. These 3 areas are the strongest part of the rod. I make the relief about 1/4" wide, 0.030" deep. If a rod is now forced against the crank cheek by it's neighbour, the oil can exit & fresh oil can enter the brg.
Click to expand...
We’ll check into that possibility.
I would think if 7 were bent, the bearing wear would be abnormal. It’s ok. Twisted, maybe? I would still expect some abnormal wear on the rod(s) and/or bearing(s). It’s still something to look into.
Edit: Also, Abby Normal piston skirt wear, as I was reading about earlier today.
 
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It is not just a bent rod that can cause the neighbouring rod to fail. Piston pin drilled at an angle, detonation, pin hole in the rod, etc. The simple fix in post #13 takes care of all the possibilities. I cannot take credit for the idea, as I saw these grooves in Crower rods, which gave me the idea...
 
Here's an update on this project:

I found a shop just north of Philadelphia whose owner answered the questions I had satisfactorily. As I mentioned in post #1, I'm not the most experienced engine mechanic, as such, I couldn't be sure I asked him all the right questions, but the ones I did ask spurred on good conversation with him (probably 20 minutes worth).

He polished the mains. (Still at .010") They are between 2.7990 and 2.7995. Standard is 2.8095 and 2.8105. A bit under. EDIT: Last time I put it together, they were all between 2.7990 and 2.8000.

There was a major step on the #8 journal that I initially didn't see. We hoped it would clean up at .020, (was .010) but he had to take them to .030. Rod journals are now all 2.095.

I theorized that the existing balance job would be okay, because the weight removed by grinding was replaced by a thicker bearing, and he agreed. (The PO had balanced the assembly to the KB190's.)

He resized all the con rod big ends. The spec is: 2.2500-2.2505 (From my research.)
Mine are all between 2.2501 and 2.2507. I measured them with a dial bore gauge and a mic. (Mic zeroed, bore gauge set to it, etc.)

Here's something that's puzzling me. The main clearances Plastigage at .003. Using the dial bore gauge, they all come in at .004 - .0045. I checked them at least 3 times, re-checking the mic and bore gauge, torquing one cap at a time, and torqing all of the caps at once. My assembly notes from the last time I assembled it show .002-.003. I only plastigauged them the last time, no bore gauge used. I've read about .003 being the most you want (strip and very little street use). I didn't have oil pressure issues before. Maybe after I drain the break in 10W30 oil, I'll try 10W40?

On the rod bearing clearances, I only used the bore gauge. I torqued the ARP bolts to 45#, using ARP's grease."Up and down", they are all between .0028 and .0033. Diagonally, they are all between .0015 and .002.

Oh, the crank run out is .000 on #3 using #1 and #5 bearings. The end play is .003.

Other than that extra on the mains, I'm very happy. And if I don't have to go another .010 on the mains, I think I'll run it. (I don't think I can get a .010 main bearing that is .001 thicker, but I need to check.

BTW, the bearings are Kings. CR 805SI 030 rods, and MB 517SI 010, per the crank grinder's recommendation. (He also machines and builds complete engine, including cyl. head work.)

Thoughts and opinions, please. :):usflag:
 
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I’ve seen comments from pros here about not hesitating with .003-.004 main clearance.

Curious why yr getting .001 tighter readings with the plastigage. And consistently.
I just put a short block together with -.001 bearings and got readings at .003” with plastigage… wonder what my hot idle oil pressure will be haha. Especially if my plastigage is reading .001” tight
 
A couple of things I noticed. The rod journal shown on your crank has what looks like a step on each end where you would normally see a radius or fillet. Right where the cast finish meets the machined finish. Hard to tell from just one photo, but that looks fishy to me. You don't want sharp corners on a crank journal, it concentrates stress in that location. That's the main purpose of the fillet.

1751066121534.png


The other thing I noticed is your spun bearing has what appears to be a corresponding step on the side of it, where it looks like it may have contacted the step in the crank. Look on the left side of the bearing in the pic below.

1751066251063.png


So my question would be is the bearing hitting that step in the crank? That's what it looks like from the pics.

When you reassembled the engine did you check the side clearance on the rods with a feeler gauge? I don't know what year your 360 is, but I show .006 - .014 side clearance for a '71. You should be able to torque both rods on the journal and be able to physically move them fore and aft with your hand a bit.

A related question. Once you get your new parts and are ready to reassemble, take some layout blue (a black sharpie works in a pinch) and put it on the side of the rod and bearing. Assemble a rod on the journal in the orientation it will have when running. Shove the rod fore or aft against the crank cheek and rotate it a revolution or two by hand while holding pressure against the crank cheek. Take the rod back off the crank and look at the bluing/sharpie ink. What is hitting first when the rod stops moving fore or aft and it contacts the crank? You don't want it to be the side of the bearing.


Again, hard to tell from just a couple of pics, but that caught my eye.


Cheers.
 
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I always seem to get plastigage to read tighter that actual. Most recently on a 408 I'm putting together. I chalk it up to the tiny bit oil residue on the crank journal. It doesn't take much to throw the reading off. A mic and dial bore gauge are hard to beat.
 
Kuz said:
A couple of things I noticed. The rod journal shown on your crank has what looks like a step on each end where you would normally see a radius or fillet. Right where the cast finish meets the machined finish. Hard to tell from just one photo, but that looks fishy to me. You don't want sharp corners on a crank journal, it concentrates stress in that location. That's the main purpose of the fillet.

View attachment 1716423550

The other thing I noticed is your spun bearing has what appears to be a corresponding step on the side of it, where it looks like it may have contacted the step in the crank. Look on the left side of the bearing in the pic below.

View attachment 1716423551

So my question would be is the bearing hitting that step in the crank? That's what it looks like from the pics.

When you reassembled the engine did you check the side clearance on the rods with a feeler gauge? I don't know what year your 360 is, but I show .006 - .014 side clearance for a '71. You should be able to torque both rods on the journal and be able to physically move them fore and aft with your hand a bit.

A related question. Once you get your new parts and are ready to reassemble, take some layout blue (a black sharpie works in a pinch) and put it on the side of the rod and bearing. Assemble a rod on the journal in the orientation it will have when running. Shove the rod fore or aft against the crank cheek and rotate it a revolution or two by hand while holding pressure against the crank cheek. Take the rod back off the crank and look at the bluing/sharpie ink. What is hitting first when the rod stops moving fore or aft and it contacts the crank? You don't want it to be the side of the bearing.


Again, hard to tell from just a couple of pics, but that caught my eye.


Cheers.
Click to expand...

On a Mopar,,,,all the cranks had an undercut filet from the factory .
They didn’t use a radius on the edge of the journals,,,still worked pretty good .

Tommy
 

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