piston resizing
 

have some good JE super stock pistons that I would like to resize for a smaller bore size. I broke the crankshaft in my engine and it ruined the block. I need a new block but don't want to bore it out to the max on the first go around. Can this be done

Re: piston resizing
 

Possibly, depends on how much you are talking about,most likely ring lands would also have to be made deeper also,unless rings could be back cut enough,but they may already be as thin radially now as can be.
Might talk to Eric @ Rebco,he does piston mods,not sure about diameter though.
Mike Taylor 3601

Re: piston resizing
 

They are for a 4.075 bore now. I would like to go down to 4.065 if possible. That would be .005 off the radius.

Re: piston resizing
 

Show a pic of the bottom of the piston, and measure how thick the strap is below the wrist pin hole, it may be possible.

Re: piston resizing
 

Piston skirts are usually not cylindrical. Some times they are some combination of tapered, cam ground, barrel shaped.
I wonder if JE can resize them.
https://www.jepistons.com/Catalogs/Automotive/NHRA.aspx

As others said, the ring grooves may need deepening. I don't think that can be done without the ring seal suffering,

Re: piston resizing
 

Call Frank Parks. He has started doing pistons for the Nostalgia Dragster crowd. He might be able to give you some advice or even do what you want.
His Son Scott is very talented and can do just about anything with a CNC.

Re: piston resizing
 

Thanks Adger. Can you send me a Pm with his contact info or text to 813-433-4742

Re: piston resizing
 

Hi,
Normally, OEM piston skirts are tapered horizontally and vertically.
The top land is also tapered from the chamber down to the top ring groove.
All the land diameters are specially sized too.
Ring grooves should be adjusted appropriately as well.

Trying to resize the piston will be difficult with the center boss removed.

Resizing a piston without a properly tapered shape would be a concern for scuffing,...especially for high rpm, high load applications.

Thanks, Ron

Re: piston resizing
 

Most piston skirt shapes on racing pistons that make good power are a near straight profile in the Z axis, with a non-linear radial profile leading to the oil ring groove and a smaller yet non-linear radial profile at skirt bottom, all the while also cutting a variable elliptical shape. The CNC lathe that accomplishes this is about a 1/2 million dollar investment, so not something that can be done on the usual shop equipment.

Trying to recut the ring grooves deeper, yet maintaining the same ring groove width will ruin them, best option is to back cut any rings as necessary if possible.

If there isn't enough cross section remaining in the bottom of the piston to re-machine a locating register to hold the piston with while machining, then all of this discussion is moot. That's why I asked for a picture and measurement previously, I likely designed your pistons in the first place.

Re: piston resizing
 

Thanks for the reply Rick. Can you send me an e mail address to send some pics to you. PM me or e mail me at ssia2485@yahoo.com with your contact info. Thanks again for your reply's