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School me on Pistons....

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  #11  
Old 12-19-2017, 09:13 AM
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BTW,, If while hunting for pistons avoid the wisecos that have 2mm oil ring grooves.. They have issues and it's not cuz they are slipper.
 
  #12  
Old 12-19-2017, 09:58 AM
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Originally Posted by Max Headflow
As far as I know skirts on narrow skirted pistons are the same length as full skirted ones unless the build is different (bore, stroke, rod length). You want resistance for the pivoting on the pin. It should float. I don't see how it would make any difference between the 2 piston types. Piston skirt, narrow or wide wears mainly on the thrust sides (front and back) where the skirts are located on a narrow skirt piston. The piston pin / rod keep the pistons from rocking where there isn't any skirt.

I have a 02 RKC (about 80K) with about 60K on a set of 95 ci 10.8 to 1 slipper skirt early wisecos. It's easily had 100 dyno pulls at various times, made as much as 110 hp, had ccps as high as 220 psi (depending on the cams) and been run hard at times even with temps over 100F. It hasn't blown up yet. Burns maybe 1/2 qt in 3000 miles.

I'm not worried.
The full skirt reinforces the the area that the narrow skirt contacts the cylinder wall. I have partial skirts on mine as well, but I also run around 100 HP and lower RPMs. Racing pistons are full skirted for a reason, but I agree, are unnecessary in most street builds.
 
  #13  
Old 12-19-2017, 07:28 PM
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Originally Posted by Jay Guild
The full skirt reinforces the the area that the narrow skirt contacts the cylinder wall. I have partial skirts on mine as well, but I also run around 100 HP and lower RPMs. Racing pistons are full skirted for a reason, but I agree, are unnecessary in most street builds.
Yeah.. I think you are right.. They will probably only go about 80K.
 
  #14  
Old 12-19-2017, 07:38 PM
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Originally Posted by Jay Guild
The full skirt reinforces the the area that the narrow skirt contacts the cylinder wall. I have partial skirts on mine as well, but I also run around 100 HP and lower RPMs. Racing pistons are full skirted for a reason, but I agree, are unnecessary in most street builds.
Is this a narrow skirt piston?



 
  #15  
Old 12-19-2017, 08:34 PM
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Originally Posted by Max Headflow
Is this a narrow skirt piston?



Looks like a slipper skirt. My info above is from Randy Torgeson (aka: King of Cubes) who has 40 years building motorcycle engines and apprenticed under the owners of Zippers and Axtell in the 80s. Other than that I don't know what to tell you.
 
  #16  
Old 12-20-2017, 10:21 AM
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Originally Posted by Jay Guild
Looks like a slipper skirt. My info above is from Randy Torgeson (aka: King of Cubes) who has 40 years building motorcycle engines and apprenticed under the owners of Zippers and Axtell in the 80s. Other than that I don't know what to tell you.
Well those are stock SE 103 pistons.. Not sure what gave Randy bad feelings towards slipper skirt unless the design was poor.. You might need to give a specific piston to avoid. For instance. Certain versions of Wiseco TC pistons had issues due to 2mm oil control rings. That has been fixed. IIRC some Ross TC pistons had issues but don't remember exactly what the issue is was.

Heck Revolution performance once claimed that CP pistons collapsed skirts but I suspect that it was cylinder finish causing the issue..
 
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