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Can i use the stock (not cut) pistons in my engine build? I have heard differing opinions. Goal is to have a 750ish hp truck to run low 11's maybe a high 10. all opinions appreciated.

Kelly
 

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Can i use the stock (not cut) pistons in my engine build? I have heard differing opinions. Goal is to have a 750ish hp truck to run low 11's maybe a high 10. all opinions appreciated.

Kelly
I'd cut them, but that just an opinion.
 

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750 RwHp is going to be putting any stock piston at it's limit, cut or not.
 

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I would cut the pistons as a minimum precaution. It both lowers the compression and makes the piston more resistant to melting or cracking.

We ran Casper at 750 horse for a short with stock pistons and they survived, but perhaps only because the rods bent and lowered compression.
 

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Cut or forged pistons.

Cut you still might crack.
 

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how many stock pistons have cracked that were cut and not lbz's ?
 

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I have seen all the stock pistons crack. Cut or uncut they crack at some point. Trying to figure out why is the issue. While some work just fine others do not.
 

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so for a daily driver/weekend sled puller a cut lb7 piston is the way i was thinking of going. and running a compression of about 15:1. from what i've read i can't put alot of road miles on my truck with the forged pistons, correct? or is the jury still out on that....
 

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At this point on the forged pistons the jury is still out. A cut stock pistons have worked for some and failed for others. So for right now it's a hard call as to what will work out in the long run. The best anyone can do is give an opinion, so it's up to you which poison you want to pick. Keeping the power down is the safe pick but who wants to do that.
 

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so for a daily driver/weekend sled puller a cut lb7 piston is the way i was thinking of going. and running a compression of about 15:1. from what i've read i can't put alot of road miles on my truck with the forged pistons, correct? or is the jury still out on that....
Right now, as of today, if you ask the guys who are running big power, "what is working", the answer is cut pistons. It will take years to find out from truck owners what to expect for a normal lifespan from the cast Dmax pistons.

There have been alot of competition pulling trucks running forged pistons for a long time now with success, but normally they blow up and are rebuilt before piston life becomes an issue.

Forged pistons work excellent in a gasoline world for long life, but it is not realistic to expect them to outlast the uber-trick cast pistons our engine are delivered with. The internal oiling, cast in pin support, ring land insert, etc, are all designed to maximize piston life at high temps.
 

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why do they lower compression in a cummins? (real question here) i thought one of the main reasons was becuase of rpm
 

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Given the right circumstances any piston can fail.

What we know as of today is a cut LB7/LLY has a greater success rate in high HP trucks that are also driven on a daily basis.
 

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when you guys(no pun intended!) are saying cut, are you saying cut off the top, or taking the lip out of the bowl? or both
 

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i was under the impression it was both, but important thing was to be sure of valve-piston clearance depending on the camshaft that is in the motor?
 

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when you guys(no pun intended!) are saying cut, are you saying cut off the top, or taking the lip out of the bowl? or both
Removing the lip takes an LB7/LLY from 17.5 to 16.8 (LBZ ratio).

Then remove more from the top, for piston to valve clearance and/or compression ratio reduction.

Or cut valve reliefs for piston to valve clearance. If you cut valve reliefs, be sure to leave a generous radius in the bottom of the relief.
 

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If I was to do mine all over again, I'd just remove the lip, add a big radius and leave the top alone.
 

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anyone care to share the specs of the way they cut pistons? like radius, etc....
 
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