What the diff between these 2 pistons?

Light It Up

Light It Up

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Oct 22, 2008
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How come #3 piston still looks new and all the others dont? I just bought this engine and it was recently rebuilt but spun a rod bearing. Just thought I would ask you guys.
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Had an 06 in the shop a few weeks ago that looked just like that. It looked like the #6 piston was hitting the valves, but it was actually the piston hitting the head. We thought it was a wrist pin wore out but once we tore into it, it was the rod bearing spun and the rod cap broken in half. Don't see how it was still running. A wore out wrist pin will cause this too.

To check to make sure that is what is happening, turn the engine over by hand till that piston is on TDC. Then jerk the crank shaft on over some so that the piston starts its way down. Then push down on the piston to see how much it moves. If the rod bearing is spun bad enough it will cause enough slack for the piston to jump up some and hit the head when running.
 
Also just to add. The truck sounded like it had a rod knocking, but it was more at the top of the engine. What we was hearing was the piston hitting the head, not the rod slapping around. If this was a fresh rebuild, it maynot be a rod slap that you are hearing. It maybe the piston hitting the head from just a wore out wrist pin. You will know more once you have tore into the engine farther.
 
Thank you kino fab I will check to see if the piston has any play in it because of a wrist pin.

How much does it cost to get a crank turned and should a guy if its not to bad or just put in a new crank? I have a good crank out of a rotary pump engine that I can put in it. Also thinking about swaping everything over into to a brand new 12v Industrial block that I have that is sleeved already. What are your thoughts? Thank you very much for the help!
 
Might be cheaper to go with the other crankshaft. If that engine spun a rod bearing after a rebuild, thier maybe oiling problems with that block, or the builder didn't get his tolerances right with the rods and bearings. Using either block would be fine, but I would take everything to a machine shop to have everything checked and rebalance the bottom end.
 
I think I should use the new industrail block along with the good crank out of the other block. I think this crank could be saved but If Im goin with a new block I dont think I should even bother with it. I also thought about just buying the rebuild kit from Pure Diesel that way I have new pistons with the bigger bowls. These pistion do have some minor scratches. Do you think this would be a smart decision? Lookin for upwards of 600-800 hp with this motor.
 
What about taking the crank out of my 24v engine with 120k miles. I know its good. Is there any diff between the two cranks?
 
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