Crankshaft questions, pics inside
Crankshaft questions, pics inside This is going to be my first motor build, so appropriately I sourced a cheap long block. Upon disassembling it I noticed rod bearings on #8 were scored, and there is minor scoring on the crankshaft, and a small dent.
I also noticed in the oiling passages there is metal shavings, due to the bearing failure I'm assuming.
You can also see some scoring on the crank, but I can't feel it with my finger or nail. I can feel the dent.
Does this crank need to be turned, and if so what are my bearing options? The motor is going to see high RPMs, right now I have Crower rods and JE Pistons for it.
Also, the pistons are factory replacements. I know the factory rod is 6.098 and the crower rod I am using is 6.125. That leaves the piston .027 above the deck, and JE specs it already being .010 above the deck. Can I still run the newer MLS gasket or do I need to goto something like a Cometic?
The heads I will be using are milled .030, if that helps any.
Any input is appreaciated, thanks!
I also noticed in the oiling passages there is metal shavings, due to the bearing failure I'm assuming.
You can also see some scoring on the crank, but I can't feel it with my finger or nail. I can feel the dent.
Does this crank need to be turned, and if so what are my bearing options? The motor is going to see high RPMs, right now I have Crower rods and JE Pistons for it.
Also, the pistons are factory replacements. I know the factory rod is 6.098 and the crower rod I am using is 6.125. That leaves the piston .027 above the deck, and JE specs it already being .010 above the deck. Can I still run the newer MLS gasket or do I need to goto something like a Cometic?
The heads I will be using are milled .030, if that helps any.
Any input is appreaciated, thanks!
You might want to take the crank to a local machine shop and see if they can polish it for you. Some of the scoring might clean up and keep you from having to have it turned. After polishing it you will have a good idea as to wether or not the crank needs to be turned. If so you can go -.010" and still have a good selection of bearings.
If you have any questions please feel free to call us.
Thanks
If you have any questions please feel free to call us.
Thanks
TECH Apprentice
Joined: Apr 2003
Posts: 372
Likes: 0
From: Orlando, FL
you might want to find a piston designed for the 6.125 rod........ you spent the money on crower rods, spend the money on the proper piston.
And if the crank won't clean up.. I'm sure you can find another crank cheaply.... like a used ls1 crank.. same stroke, and it's gun drilled IIRC.
And if the crank won't clean up.. I'm sure you can find another crank cheaply.... like a used ls1 crank.. same stroke, and it's gun drilled IIRC.
I would prefer to use my parts as is, they are sort of oddball. Crower 6.125 rods with the stock pin diameter (.945) and pistons with the same. I was thinking I would need to run a thicker head gasket than .052? Something around .070-.080?
Any input here on the piston sticking out around .037ish? Is that calculated correctly?
Anyone have any ideas on the compression this will be? They have -2 cc valve reliefs.
Any input here on the piston sticking out around .037ish? Is that calculated correctly?
Anyone have any ideas on the compression this will be? They have -2 cc valve reliefs.
TECH Fanatic
Joined: Apr 2003
Posts: 1,109
Likes: 0
From: Albuquerque, NM
I think the crank will be OK with a polish only like Chris suggested. I have a galled crank that the bearing material "bonded" to the journal due to oiling issues. I picked up a used crank on Ebay for about $90 shipped. If you go the used route remember that the 5.3L truck engine uses the same crank as all the LS1 motors except the 4.8L. Gives ya more options.
The rod/piston geometry makes me kinda nervous. Using just the stock pin diameter and longer rod length may not be totally accurate. Check with JE for the piston deck height ( rod pin to crown ) and compression height. There are sometimes huge differences ( like up to 0.200" ) in some cases.
I think the -2cc valve reliefs with "normal" compression height and 64cc heads gives around 10.8:1 compression. There is a good thread at the top of this section with all the rates for the different volumes and for the head shave.
Good luck, let us know how things come out!
The rod/piston geometry makes me kinda nervous. Using just the stock pin diameter and longer rod length may not be totally accurate. Check with JE for the piston deck height ( rod pin to crown ) and compression height. There are sometimes huge differences ( like up to 0.200" ) in some cases.
I think the -2cc valve reliefs with "normal" compression height and 64cc heads gives around 10.8:1 compression. There is a good thread at the top of this section with all the rates for the different volumes and for the head shave.
Good luck, let us know how things come out!
I measured from the top of the pin bore to the top of the piston, it is .867
1.340 compression height
I am not sure if a polish will clean the dent in the crack out, but I'm sure it will take out the scoreing. Will that tiny tiny dent cause any problems with oiling or anything else?
1.340 compression height
I am not sure if a polish will clean the dent in the crack out, but I'm sure it will take out the scoreing. Will that tiny tiny dent cause any problems with oiling or anything else?
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TECH Fanatic
Joined: Apr 2003
Posts: 1,109
Likes: 0
From: Albuquerque, NM
I don't think that dent will cause any problems. Too small to be of any issue unless it is in the spacing between the rods. Then maybe you could experience some sealing loss.
One other thing to check is the clearance on the #8 piston skirt to the reluctor wheel. Some aftermarket piston and rod combos have been known to make contact at the bottom of the stroke. Clearance should be at least 0.030".
One other thing to check is the clearance on the #8 piston skirt to the reluctor wheel. Some aftermarket piston and rod combos have been known to make contact at the bottom of the stroke. Clearance should be at least 0.030".
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