piston to wall clearance?

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im finally taking my block in to be machined, and the machinist needs to know what the piston to wall clearance should be. Apparently the piston manufacturer should have included the specs but they didn't.
the manufacturer is mahle.
what is the best clearance for the 6.0 with .020 over pistons?
 

Zeb

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It usually has the piston to wall clearance on the side of the Mahle box.
That being said it is 0.0037” on the last set of 0.20” 6.0 pistons I bought from them. I had the machine shop bump that out to 0.0045” because it was not a stock application. With the ptw at 0.0045” the top ring end gap was 0.020”, the middle rings were 0.059”-0.062”, and the bottom rings were 0.017”. I also delipped them and took 0.015” off the top because the block deck height was 11.015” and we were running a Colt Stage 2 cam.
 

Cutting-Edge Diesel

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Here is the specs on the box. But my machinist gives it a little more clearance as well. Don’t remember exactly what he punches it out to.
 

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ok thanks for the info.
i'm also running a colt stage 2 cam and the piston has .030 taken off so very similar.
what is the purpose of the extra clearance?
 

Zeb

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The goal is to eliminate skirt scuffing and to keep the rings from butting.
More power makes more “instant heat” and the additional ptw clearance allows for the corresponding piston growth that a situation like that generates.
 
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thanks for your help guys.
Engine finally went in for machining today.....just another fire breathing 6.0 comin down the pipeline! :fordoval:
 

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