Spun Rod Bearing
Spun Rod Bearing A month ago my motor locked up idling while pulling into a parking spot. I tore the motor down and turns out the oil pump was locked up but everything else looked alright and I threw it back together with a new pump. Car had 75 psi of oil pressure on cold start and 40 at hot idle. Never drove the car, just ran it in the driveway. Once it got hot I revved it up to around 4k rpm and when it started dropping I could hear the slightest knocking. Pulled it apart knowing it has bearing problems and here are pictures of what I found. Just the #6 rod bearing got spun, but doesn't look too bad. I don't think crank can be turned anymore and block can not be line honed or bored anymore. If damage isn't bad is it possible to fix this without getting a complete re-build with another block and crank?
Other Rods (Appear alright to me):
Spun Rod:
Bad Bearings Inside:
Bad Bearings Outside:
Crank Damage:
Other Rods (Appear alright to me):
Spun Rod:
Bad Bearings Inside:
Bad Bearings Outside:
Crank Damage:
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From: Norn Iron
Unless the crank had actually seized in the block, then the block will be perfectly fine.
The rod in which the bearing spun, needs replaced.
The crank.....again, is it stock or aftermarket ? if stock, I'm sure it would be cheap and easy to find a good replacement, which would save having to have yours reground.
Or at a push, have the crank inspected by a local machine shop, and it may be ok. But pretty sure stock cranks are very cheap....so why bother ?
Really cant see any reason why a rebuild would need to cost a fortune.
new rods, new bearings, new pump, thoroughly clean all oilways etc, and it should be good to go.
What is the actual question ? What do you mean by the crank can be turned ?
Unless the crank had actually seized in the block, then the block will be perfectly fine.
The rod in which the bearing spun, needs replaced.
The crank.....again, is it stock or aftermarket ? if stock, I'm sure it would be cheap and easy to find a good replacement, which would save having to have yours reground.
Or at a push, have the crank inspected by a local machine shop, and it may be ok. But pretty sure stock cranks are very cheap....so why bother ?
Really cant see any reason why a rebuild would need to cost a fortune.
new rods, new bearings, new pump, thoroughly clean all oilways etc, and it should be good to go.
Unless the crank had actually seized in the block, then the block will be perfectly fine.
The rod in which the bearing spun, needs replaced.
The crank.....again, is it stock or aftermarket ? if stock, I'm sure it would be cheap and easy to find a good replacement, which would save having to have yours reground.
Or at a push, have the crank inspected by a local machine shop, and it may be ok. But pretty sure stock cranks are very cheap....so why bother ?
Really cant see any reason why a rebuild would need to cost a fortune.
new rods, new bearings, new pump, thoroughly clean all oilways etc, and it should be good to go.
It is a stock crank and it turns freely.
So all it needs is another stock crank, rod, rings, bearings and have it thrown back together?
New crank can be used with my block? What would machine shop have to do to get that to work? line hone?
9 Second Club
Joined: Nov 2003
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From: Norn Iron
If any rod bearing has spun, IMO the rod must be replaced. So if you are sure only one has, then you could get away with one rod.
But TBH, a full set of new rods is pretty cheap all things considered.
Unless you are honing the bores, or the rings etc have been damaged. There is absolutely no reason you should be buying new rings.
So yes. Source a good stock crank ( should be easy ), new bearings, new rod, new pump, thorough clean and rebuild.
But TBH, a full set of new rods is pretty cheap all things considered.
Unless you are honing the bores, or the rings etc have been damaged. There is absolutely no reason you should be buying new rings.
So yes. Source a good stock crank ( should be easy ), new bearings, new rod, new pump, thorough clean and rebuild.
If any rod bearing has spun, IMO the rod must be replaced. So if you are sure only one has, then you could get away with one rod.
But TBH, a full set of new rods is pretty cheap all things considered.
Unless you are honing the bores, or the rings etc have been damaged. There is absolutely no reason you should be buying new rings.
So yes. Source a good stock crank ( should be easy ), new bearings, new rod, new pump, thorough clean and rebuild.
But TBH, a full set of new rods is pretty cheap all things considered.
Unless you are honing the bores, or the rings etc have been damaged. There is absolutely no reason you should be buying new rings.
So yes. Source a good stock crank ( should be easy ), new bearings, new rod, new pump, thorough clean and rebuild.
I'm sure only one rod was spun. Bores and rings look fine, I just figured it would be a good time to replace them.
Have a new Texas Speed ported LS6 pump already.
So what do I need a shop to do? I can't just re-assemble with new rod, crank, and bearings can I...?
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9 Second Club
Joined: Nov 2003
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From: Norn Iron
I guess a real stickler would say that the rotating assembly would need balanced crank/rods/pistons.
Ive no idea whether you had this carried out on the original build or not.
But it isnt essential. Ive built 346's before by just fitting rods/pistons to a stock crank, and never had any issues.
So up to you really.
Cheapest is just to rebuild as mentioned. No machine shop required providing you are competent to do the work.
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Verdad Gallardo If the rings have been sealing fine, no blowby and the rings are in good order. There really is little reason to replace them. If you do replace them, the bores MUST be re-honed so the new rings can bed in, which will require running in again.
I guess a real stickler would say that the rotating assembly would need balanced crank/rods/pistons.
Ive no idea whether you had this carried out on the original build or not.
But it isnt essential. Ive built 346's before by just fitting rods/pistons to a stock crank, and never had any issues.
So up to you really.
Cheapest is just to rebuild as mentioned. No machine shop required providing you are competent to do the work.
I guess a real stickler would say that the rotating assembly would need balanced crank/rods/pistons.
Ive no idea whether you had this carried out on the original build or not.
But it isnt essential. Ive built 346's before by just fitting rods/pistons to a stock crank, and never had any issues.
So up to you really.
Cheapest is just to rebuild as mentioned. No machine shop required providing you are competent to do the work.
Exotic Performance built it and I was told it was balanced but I don't see where any material was removed or added to rods or pistons. They each have the cylinder # engraved on them though.
I have built the entire car so I would like to think I'm capable of doing it, just never attempted it.
So if I get a new stock crank that is good and never been turned I can just get a new set of bearings matching the part # on my current ones and it should be good to go? of course a new rod too
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Joined: Nov 2003
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From: Norn Iron
Most of the balancing will be adding/removing material from the crank.
Likely the rods and pistons are made well enough that virtually no balancing of these individual components is required.
Whilst you can DIY hone, you'll never create the same finish a proper machine shop can. But it is certainly do-able.
Likely the rods and pistons are made well enough that virtually no balancing of these individual components is required.
Whilst you can DIY hone, you'll never create the same finish a proper machine shop can. But it is certainly do-able.
Most of the balancing will be adding/removing material from the crank.
Likely the rods and pistons are made well enough that virtually no balancing of these individual components is required.
Whilst you can DIY hone, you'll never create the same finish a proper machine shop can. But it is certainly do-able.
Likely the rods and pistons are made well enough that virtually no balancing of these individual components is required.
Whilst you can DIY hone, you'll never create the same finish a proper machine shop can. But it is certainly do-able.
Cant see how bad the crank really looks but how deep are the marks on the crank? You might be able to get it polished and it may be fine. IMO I would also replace that rod and like stevie and others said the rings/bore should be fine. I would also get the rotating assy. balanced while its out. Just make sure the rings stay in the exact order and bore! lol
Here is my thinking on having the block tanked and measured. The friggin' motor froze up due to the oil pump failure. I doubt the spun bearing in unrelated. Cheap is good but not if you miss something.
I can assure you that many, many dirt track cars suffer this type of damage every weekend, and the repair job involves nothing more than gaskets, 3M scotch-brite pads, a few new bearings, and maybe an oil change. I am not saying it is perfect, I am just saying that it happens all the time on low budget race engines.
Driving habits? Run hard with cold oil? What oil type?
Last edited by twinturbo496; Jan 8, 2011 at 01:02 AM. Reason: added maybe
9 Second Club
Joined: Nov 2003
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From: Norn Iron
When rods are so cheap why on earth would you take a risk ?
Cant see how bad the crank really looks but how deep are the marks on the crank? You might be able to get it polished and it may be fine. IMO I would also replace that rod and like stevie and others said the rings/bore should be fine. I would also get the rotating assy. balanced while its out. Just make sure the rings stay in the exact order and bore! lol
One of the photos shows discoloration of the rod, depending on the budget, and also on the expectations of the owner, you could say it needs to be replaced.
I can assure you that many, many dirt track cars suffer this type of damage every weekend, and the repair job involves nothing more than gaskets, 3M scotch-brite pads, a few new bearings, and maybe an oil change. I am not saying it is perfect, I am just saying that it happens all the time on low budget race engines.
Driving habits? Run hard with cold oil? What oil type?
I can assure you that many, many dirt track cars suffer this type of damage every weekend, and the repair job involves nothing more than gaskets, 3M scotch-brite pads, a few new bearings, and maybe an oil change. I am not saying it is perfect, I am just saying that it happens all the time on low budget race engines.
Driving habits? Run hard with cold oil? What oil type?
Plan is to just re-build it with the help of a buddy who works at a local machine shop. I need to remove crank today and see what the main bearings look like and how much that was turned / honed when main studs were added. Bores will be honed at the machine shop and we will balance it and replace all the bearings, rings, and the rod. Figured now is the time and I can get it done for under 1k.
Any suggestions on bearing type or brand? It had Clevite in there but I need to go look at them and try and see what kind.
