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Discussion Starter #1
I run 370ci turbo setup. Very simple LQ9 block bored .030 w/ a stock 6.0 crank. I recently noticed that I was down about 5 psi of hot idle oil pressure. Pulled the filter and found some bearing material. Tore it down and had some pretty good wear on mains #3 and #4 was just getting ready to spin. Pulled it out and brought it to my machinist to check out and found that it's bent .006. He said to just get another one as it would cost me more to turn it and rebalance than to replace it and balance the new one.

Know on to my question. I have a buddy with a good 5.3 crank. My understanding is that the stroke is the same but the machinist is concerned with the balancing as it would add significant cost to the balancing if material is required in order to get it right. So my question is should the 5.3 crank work for me or will material need to be added in order to get it balanced correctly? I'd like to know this before my buddy goes thru all the trouble of taking it out of the block that it is currently housed in.

I appreciate any and all input. Thanks!
 

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I run 370ci turbo setup. Very simple LQ9 block bored .030 w/ a stock 6.0 crank. I recently noticed that I was down about 5 psi of hot idle oil pressure. Pulled the filter and found some bearing material. Tore it down and had some pretty good wear on mains #3 and #4 was just getting ready to spin. Pulled it out and brought it to my machinist to check out and found that it's bent .006. He said to just get another one as it would cost me more to turn it and rebalance than to replace it and balance the new one.

Know on to my question. I have a buddy with a good 5.3 crank. My understanding is that the stroke is the same but the machinist is concerned with the balancing as it would add significant cost to the balancing if material is required in order to get it right. So my question is should the 5.3 crank work for me or will material need to be added in order to get it balanced correctly? I'd like to know this before my buddy goes thru all the trouble of taking it out of the block that it is currently housed in.

I appreciate any and all input. Thanks!

yes, it will take more mallory to balance the crank. the pistons are much lighter in the 5.3. def cheaper to get a 6.0 crank.

why was your crank bent?
 

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Can you get better pictures ? Looks like a lot of fretting occured on that cap in the pictures.got pictures of the rod bearings ?
 

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Discussion Starter #6
Looks like #4 shrunk up. Lack of oil. You may also want to go ahead and pin the main caps as well while you are at.


Chris
I'm not getting into doing any machine work. This is a one week deal that may turn into a 2 week deal at the most. I just don't have the finances to get into all that right. Believe me, I would if I could.
 

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Discussion Starter #7
Can you get better pictures ? Looks like a lot of fretting occured on that cap in the pictures.got pictures of the rod bearings ?
I have the bearings with me and can get a better picture but the block and caps are at my buddy's house where I pulled the motor. There is only one rod bearing with visible wear. I'll get a couple of better pictures of the 2 bad ones in a minute.
 

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Discussion Starter #8 (Edited)
About the best that I can do. The second one with the least wear is the only rod bearing that should any wear. The other rod bearings just had real lite scratched that appeared to be from the debris that was flying around from the chunked up mains. I only have one side of the thrust bearing. May have left the other side of it at the machinists shop. The really bad ones arethe top and bottom of #4.





 

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I have a 6.0 crank ill put on ya cheap if it would help...
 

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do you have a stock oil pan on this?
 

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Look at the crank throw where they would be sitting with the top of the bearing shell fothe rod at TDC, do you see any signs of witness marks ? Just a curiosity, those bearings look overheated, hard to say if its from lack of oil control or fron the crank wobbling. They certainly show heat stress though for sure.


About the best that I can do. The second one with the least wear is the only rod bearing that should any wear. The other rod bearings just had real lite scratched that appeared to be from the debris that was flying around from the chunked up mains. I only have one side of the thrust bearing. May have left the other side of it at the machinists shop. The really bad ones arethe top and bottom of #4.





 

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Discussion Starter #15
Look at the crank throw where they would be sitting with the top of the bearing shell fothe rod at TDC, do you see any signs of witness marks ? Just a curiosity, those bearings look overheated, hard to say if its from lack of oil control or fron the crank wobbling. They certainly show heat stress though for sure.
I'm not understanding exactly what it is that you want me to look at. The crank main or rod journal or the bearing for the rod or crank?
 

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Probably mains were too tight. Crank is warped from getting hot so it's also probably not cracked. You should be able to straighten it but if you have a new one might as well use that. If it has a lot of heat and still spins nice it has usually stress relieved itself and is cracked and usually junk. You don't usually need to rebalance after turning a crank really.
 

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Have your machinist check the crank for twist. If it's twisted, it'll show to be bent too.
 
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