How much piston to cyl clearance can we get by with?

78f100

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What is the max piston to wall clearance you guys would run on a 6.4? My old block definatly needs boring but I bought a spare motor that measures out good except one cly # 8. It had a blown egr cooler and bent rod in that hole. I think I can get by with honing and should end up with close to .06 piston to wall clearance.
The manual I have says factory is .018 to .037 seems kinda tight to me, but this is my first diesel engine bottom end.
 
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kdogg85

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These need to be tight due to pressure and the unreal blowby you can have. I would suggest at least sleeving it if you can't swing new pistons and rings.
 

78f100

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These need to be tight due to pressure and the unreal blowby you can have. I would suggest at least sleeving it if you can't swing new pistons and rings.

I am wanting to run IH pistons in it is the reason I'm asking. I still plan to build my other motor I will bore it .030 and use machined Ford pistons in it if the IH oversized pistons still are not available. I want the other motor for a spare, or may pick up a reg cab to put it in.

Like I said I'm not a diesel engine builder but .018 to .037 seems reall tight to me. I know they are totally dif engines but the cummins guys run way more clearance than that. And gas engines usually are looser too.
 
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78f100

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I was writing my measurements wrong add a .0 to them, I'm new at this...lol.
It should be .006 and the manual says factory is .0018 to .0037

All my measurements are correct I have tripple checked, I just wasnt writing them right.
 
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78f100

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Any one else have thoughts on this?
I read all the time where guys are just putting new IH pistons in. There is no way their cyl's are still at factory spec. Or am I wrong about this?, both my blocks have about 100k on them and are really close on bore wear. Cly 7 & 8 are always worse from the regens. Mid bore on both engines is really good but at the top of the stroke where the piston rocks is where most of the wear is.

Are folks just slapping in new pistons and not checking bores? I am curious how every one is getting by running IH pistons.
 

4.0l sahara

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I would be more worried with cylinder out of round. Have you checked to see how out of round the bore is?
 

LovinPSDs

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why not go with Elite HD pistons or something instead of just IH pistons? I believe those guys can get you a .30 over, with proper machining done, and coated.
 

Wayne

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Most of the engines we build get .020 overbore. Finding one with low enough miles to run the IH units is rare. We also have yet to crack one of our modded pistons, if that helps with your decision.
 

78f100

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Wayne, I talked to you about some pistons and for my original block thats what I plan to go with is some machined/coated .030 Ford pistons. I was just curious if I could use the IH pistons and run them a little loose for the spare motor.

I know people don't like giving away engine secrets but why do these things have to be setup so tight? I assume the stock pistons don't have much thermal growth is why. I know in gasser's if you run lots of boost or nos you need to loosen the motor up. Seems like on a truck with big turbos and more fuel you would want it a little looser, is my thinking but like I said I'm new at it.

I am not trying to get by on the cheap I am just wanting to learn about building these motors.
 

blk350on20s

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I just put a new piston in mine but it only had 45k on it and had been deleted its whole life. There was also no scoring on my cylinder. Did a light hone and popped it in
 

blk350on20s

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Nope. Just a slap and go. Just hit 94k on the way home yesterday and this motor sees its fair share of abuse
 

Fast-6.0

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We have ran motors with .006" clearance after a hone. Its not ideal but honestly a used hole with 50K miles and an out of round bore is worse than a clean hole with .006" clearance. You will be fine.
 

78f100

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Thanks Tadd, I figured someone had ran one a little on the loose side. I bet there are lots of them out there that have no idea how much clearance they have.
 
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