piston resizing

Rick Leininger Jr. · 11-10-2015, 08:09 AM

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.

11-10-2015, 08:09 AM	#7
Rick Leininger Jr. Member Join Date: Jun 2007 Posts: 162 Likes: 0 Liked 0 Times in 0 Posts	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.