Anyone re-bearing an engine with a "rough" crankshaft surface?

See alot of LS engines come through with a "record like" surface on the crankshaft. I can get these dirt cheap and they don't really seem to spin bearings much. Current setup is an alum 5.3 I'd like to get a season out of 1/4 mile drag racing for fun. Engines already in the car. Seems to have decent oil pressure (70+ cold, 30s at idle) and runs well. Pulled pan to fix massive leak and decided to pull a few caps. The rod bearings look ok and the surface on the rod journal is great.

Moved on to check the crankshaft main bearings. There are shallow record like grooves in the bearing and unfortunately the crank main journal as well. I'm aware the best practice is to pull the engine, machine crank etc.

Just curious if anyone else has been in the situation and tossed in some new bearings. If so... How far did ya get? Car would just be making 1/4 mile passes with maybe 50 miles a year cruising to car shows.   

Thanks! 

I would no recommend taking any shortcuts in the bottom end department.

There is much greater chance of the bearing touching the crank if the surface is not smooth. Once the bearing touches the crank, it's all over.

But on the other hand, Henry Velasco used to say, "Those aren't divots, they are oil reservoirs!"

Appreciate the input. I'm not concerned with damaging parts here, only to try and finish out a season. These engines are "throw aways". I wouldn't bother machining this one as the cost and wait are more than another replacement engine.  Main issue lately is finding one in good shape. It'd cost me roughly $51 to throw some bearings in this one and press on. If it munched a bearing... no harm no foul. I'd be replacing the whole short/long block anyway. 

 Remove a bearing. 
      Take some 400 grit emery cloth or wet/dry sand paper and hand polish the high spots off.    Slide the sand paper over the journal. And grab each end and slide back and forth a few times.  Then switch to 1000 grit.

    Then rotate the crankshaft 1/3 rotation.   repeat above,  rotate again 1/3 and repeat. It will take you a few minutes per main bearing. I'm 
  Then wash those journals with brake cleaner. Put it together with cam lube on the bearing surface face only.  Don't lube the back.    It will cost you some oil pressure but  probably allow you to finish the season.  Go to thicker weight oil to recover that oil pressure. ( if you're using 5w20 go to 10w 30. Etc). 

If you do it, you will regret it.  I helped a guy rebuild an engine once, and he refused to pay for machine shop work.  Everything we did was a waste of time.  Do not do it. 

Ive emery clothed main bearings on agricultural diesel engines with good success but risk v reward was very favorable

Risk was having to rebuild the engine anyway.

Reward was getting the rest of the year out of the tractor till I had time to do it properly.

Managed to get 5 more years out of that tired engine before sending the whole tractor on down the road.  

In reply to frenchyd :

I've done that in the past.. wrap a shoe string around it and really get it humming. But I can't remove the crank from the engine. If I pull the engine out, no sense in putting it back in. I was really just wondering if anyone has run them this way before. 

ForceFed86 said:

In reply to frenchyd :

I've done that in the past.. wrap a shoe string around it and really get it humming. But I can't remove the crank from the engine. If I pull the engine out, no sense in putting it back in. I was really just wondering if anyone has run them this way before. 

 

If you remove the main caps. You can then slide the top shell of the main bearing out. That gives you room to polish the crank.   Then rotate back in new bearings and Bob's your uncle.  
     I vintage raced a Jaguar and no matter what I did, baffles, accusump, overfilling etc. wouldn't prevent the 22 quarts of oil from sliding away from the pickups to letting the engine run dry.   Saturday night the pan was dropped and I did as I told you. That allowed me to race Sunday . Monday night I dropped the crankshaft off and grabbed my next one. 
I solved that problem the way the Jaguar factory did back in 1953 •••••Dry Sump. 
   I

Were  you having oil pressure issues or other lower end problems?

If there were no issues before this, I would close it up and pretend I didn't see anything. 

The bearings and crank have matching grooves so they aren't contacting and have clearance for oil. If you put new bearing into it without machining the crank you risk having the mismatched surfaces contact and cause new problems. 

Alumninum 5.3 blocks are throw away items?... Where do you live? I'd love to dispose of yours when you're done with it 

No Time said:

Were  you having oil pressure issues or other lower end problems?

If there were no issues before this, I would close it up and pretend I didn't see anything. 

The bearings and crank have matching grooves so they aren't contacting and have clearance for oil. If you put new bearing into it without machining the crank you risk having the mismatched surfaces contact and cause new problems. 

Crankshafts move forward and back  granted only a few thousands  but those grooves are going to contact each other. At least if you polish the crankshaft  that doesn't happen. 

In reply to frenchyd :

I agree about movement, but you need to keep in mind this engine was running fine before this was discovered when the engine was opened up for a different issue.  

Since the oil pressure was reasonable and no strange noises I would suspect that at this point the grooves have self clearanced as they were created and contact is not an issue.

The bearing clearances are at a point where there is reasonable oil pressure, but once you start making uncontrolled (i.e. unmeasured) modifications you know longer know what you are assembling and taking a bigger gamble than sticking with what was working.

If there was a bearing that spun or was knocking then my suggestion would be different. Once there's a knock then there's no risk to doing what you suggested, and I've done it myself in the past.

I've done both of the following:

Pretend I didn't see anything.

Slapped bearings in it and called it good.

I have done several different engines that came to me with a slight rod knock.  Usually on  marginal cars that were not worth a new engine.  All worked fine for tens of thousands of miles, some had crank or rod grooves.  The grooves are not raised like when hard hits soft metal, they are recessed from lack of maintenance.   3.8 oldsmobuick, 2.0 GM, S14 BMW, SBF, 2.3 Lima, etc. I'm not proud to have done this, only saying in my experience it was fine.  Some of these motors limped along for years others got the E36 M3 rung out of them on and off track.

In your situation I would give it a try.  In a nice car or one that I planned to keep, get a replacement low mile engine.

By itself, grooved bearing journals are probably OK.  I mean, they're not great, but if the engine is currently carrying decent oil pressure sticking new bearings in without machining the crank will probably make things better than they are.  I've done it and gotten away with it.

The real question is "what caused the grooves in the first place and has the condition been corrected?"  Grooves in the journals are from something other than oil being pumped through the gap.  That something is usually something in the engine coming apart.  It can also be dirt or other contaminants introduced when the engine was apart for something else, from a dirty funnel or missing PCV filter or other sources. 

If the contaminant is from another part of the engine coming apart then you're not likely to buy yourself much time.  If it's just dirt from ham fisted mechanics in the past then you should be able to stick new bearings in it and run it.  Personally, I wouldn't try and polish a main journal with the crank in place.  I think that the increased bearing clearance combined with the likely hood of getting abrasive material somewhere it shouldn't be (like in the crank's internal oil passages) outweigh the reduced turbulence in the oil film.

In reply to APEowner :

In my case the grooves were from all the material that pumped through the oil when the head gasket popped, so the cause was well known.

APEowner said:

By itself, grooved bearing journals are probably OK.  I mean, they're not great, but if the engine is currently carrying decent oil pressure sticking new bearings in without machining the crank will probably make things better than they are.  I've done it and gotten away with it.

The real question is "what caused the grooves in the first place and has the condition been corrected?"  Grooves in the journals are from something other than oil being pumped through the gap.  That something is usually something in the engine coming apart.  It can also be dirt or other contaminants introduced when the engine was apart for something else, from a dirty funnel or missing PCV filter or other sources. 

If the contaminant is from another part of the engine coming apart then you're not likely to buy yourself much time.  If it's just dirt from ham fisted mechanics in the past then you should be able to stick new bearings in it and run it.  Personally, I wouldn't try and polish a main journal with the crank in place.  I think that the increased bearing clearance combined with the likely hood of getting abrasive material somewhere it shouldn't be (like in the crank's internal oil passages) outweigh the reduced turbulence in the oil film.

 

When you hand polish  a crankshaft you don't reduce the diameter at all.  All you do is eliminate the slight ridge that's raised when the debris  goes through.  
    The metal from the grove has to go someplace.  Imagine digging a ditch. The dirt from the hole is piled up on the sides . 
 That's what happens to the crank. Remove that and the groves remain but you won't have ridges cutting up the bearings. 

Definitely have had to do this at the race track. It's always held as long as we needed it to, sometimes a lot longer than expected. Trying to think of a time it hasn't worked (done maybe 5-6 times, always rods) and can't think of a catastrophe.

As much as I dislike Cletus McFarland, he did a good job of proving it was cheaper to rebuild one than blow through junkyard short blocks every weekend.  But, I do remember someone telling me about a tractor that was run out of oil and run until it broke a rod, and he picked up the chunks of the block and jb welded them back in, put a new sleeve, piston and rod in, and polished the crank with crocus cloth and put it back together with new bearings and it ran again.

frenchyd said:

APEowner said:

By itself, grooved bearing journals are probably OK.  I mean, they're not great, but if the engine is currently carrying decent oil pressure sticking new bearings in without machining the crank will probably make things better than they are.  I've done it and gotten away with it.

The real question is "what caused the grooves in the first place and has the condition been corrected?"  Grooves in the journals are from something other than oil being pumped through the gap.  That something is usually something in the engine coming apart.  It can also be dirt or other contaminants introduced when the engine was apart for something else, from a dirty funnel or missing PCV filter or other sources. 

If the contaminant is from another part of the engine coming apart then you're not likely to buy yourself much time.  If it's just dirt from ham fisted mechanics in the past then you should be able to stick new bearings in it and run it.  Personally, I wouldn't try and polish a main journal with the crank in place.  I think that the increased bearing clearance combined with the likely hood of getting abrasive material somewhere it shouldn't be (like in the crank's internal oil passages) outweigh the reduced turbulence in the oil film.

 

When you hand polish  a crankshaft you don't reduce the diameter at all.  All you do is eliminate the slight ridge that's raised when the debris  goes through.  
    The metal from the grove has to go someplace.  Imagine digging a ditch. The dirt from the hole is piled up on the sides . 
 That's what happens to the crank. Remove that and the groves remain but you won't have ridges cutting up the bearings. 

That's true to some extent.  Hand polishing a journal, particularly using the section at a time technique you described in an earlier post, does mostly remove the ridges.  However, you're still removing material that's taking up space in between the journal and the bearing and therefore contributing to the total pressure drop of the interface that allows the engine to build and maintain oil pressure. 

Once the engine is operating the bearings are operating in a Hydrodynamic lubrication mode in which the pressurized oil film keeps the bearing and crank surfaces from contacting each other.  In this mode the ridges on the crank can't score the bearing.  Ridges and other surface imperfections can cause the film to be unstable and therefore transition to mixed lubrication mode in which there's intermittent contact but that usually only occurs when the imperfections to the journal (or bearing) are perpendicular to the direction of crank rotation. 

During startup, shutdown and excessively hight loads (like under detonation) the crank operates in boundary lubrication mode and there's constant contact between the surfaces.  Under those conditions the ridges can put grooves in the bearings.  However, because the oil needs to be forced through the relatively small gap that they form, ridges with corresponding groves don't reduce oil pressure as much as not having the ridges would. 

The correct repair is obviously one in which the bearing and crank surfaces have surfaces that are within spec so doing anything other than that is going to be a gamble.  My preference for an incorrect repair is one that is likely to result in the highest possible oil pressure and the least amount of debris in the engine.  If you don't polish the crank and the ridges cut grooves in the bearings then you're still going to be ahead of where the engine is now because the new bearings will be thicker than the old and won't have the grooves that corresponds with the grooves in the crank.  If you polish the crank then you'll start with lower oil pressure than if you don't due to the missing grooves and you've got the potential for leaving abrasive debris somewhere.

Absolutely. The best repair is to do the job properly.  
  That's not what was asked.  

I should add that I also at least plastigauge the clearance to see if it is in spec.  One time even bought bearings that were .001 or .002 thicker to make up for the undersized crank.

On the other side of things my Toyota 3VZE came with multiple sizes of bearings from the factory.  You see unlike the chevys that I was used to with their .0015 range of clearance the Toyota bearings came in five sizes.  The sizes were .01 mm difference, .0004"  the clearance was exactly the same on every journal, and at 230k miles they all looked new as did the crank.  I had the motor down for a burnt valve.

I've done the emery and a shoe string thing a few times, but those cars were drivers.  If all you want to do is get through the season of drag racing, why bother?  Isn't the point of drag racing to get to the other end as quickly as possible?  Even if just for bragging rights, why do the time and buy all those reassembly gaskets just to oil up the track?

Your mileage may vary.....

Appreciate all the input! 

This was a $500 LS long block. I then sold the desirable 799 heads on for $400. Then installed the less desirable small chamber 706 heads for $50. So I have $150 in this long block. Plus of course a laundry list of other go fast goodies far exceeding that price. But my point is the motors are cheap and easily replaced. *When I can find them*. I've raced these engines for many years, but this is the first time I've hosed a crank in this manor. I was just curious what I could get away with, or if anyone else had done similar.

I don't believe "doing it right once" gets you any farther when drag racing and pushing the limits like I do. (at least with my power goals)

Built engines break and mistakes are made either way. I'd MUCH rather munch a cheap long block and just toss it that sit around for months waiting on a machine shop and spending 10x the money or more. I'm not Cleetus and I'm not spending 30-50k on a motor/driveline. If you really watch that show, he goes through engines/trans/driveline like candy. He just has the $ to keep it going. And more power to him for doing that! I can run my 8.50 cage cert easily on a cam only 4.8. No reason to overbuild IMO.  

 When I removed the Drive on demand lifters and original cam I did not change the lifter trays as I should have. This caused 4 of the lifters to move in the lifter bore and eventually start to tap loudly.  This chewed up the lifters (alot!) and sent small amount of metal through the engine. Which hosed the main bearings. Oddly enough I don't see these grooves on the rod bearings... Only the crank.  I datalog oil pressure when racing and I overfill the oil pan I see little to no drop in oil pressure on the launch. And I launch it hard. 1.2x 60' with the wheels in the air." Don't believe it was starved for oil. There is not heat in them that I can see anyway.   

I'm going to attempt to knock the bearings out and get rid of the high spots as suggested. Then toss in new bearings.  I really appreciate the input. I'll be sure to come back and note my likely failure! lol. But if there's a chance of success for $60 worth of bearings I'll take it. Meanwhile I'm sourcing a motor. I'll do my typical tricks to it and have it sitting on the side ready. 



 

In reply to ForceFed86 :

That car is amazing!