I came across an interesting article in an (ahem) non-mopar magazine (I was interested in some pro-touring stuff they reviewed). Anyway, this article describes a new technology being used by some for using pistons that are sized for a .030" over bore job for a .060" over bore - as in you want to re-use your existing pistons, or you happen to have some nice .030" pistons you want to use for a build that is .060"over. An Abradable Powder Coating (APC) is applied to the piston skirts to get a snug fit. Here's a quote from the article:
"we apply .010 - .015" of APC coating to the piston skirts to get a snug fit. After the motor is first fired up, the pistons grow and the coating abrades in areas that are too tight. Once there is room for an oil film to form, the coating stops wearing. The gage point wears the most and more coating thickness is retained elsewhere on the piston skirt....piston rock is reduced so the rings stay squarer to the bore throughout the entire four stroke cycle. Since the rings move less, they seal cylinder pressure and control oil more effectively." The APC coating is made from plastic and graphite.
Says that this technology has already been successfully used in naturally aspirated and heavy duty power adder engines in drag applications and that it only costs $30 per piston for application of a .006" typical coating thickness. They say they have different levels of hardness depending on application and the APC coating can be used for iron and aluminum blocks as well as blocks with sleeves or Nikasil coatings. No special block prep is required.
I'm a metallurgist by trade so this interests me very much, but I'm an engine builder by no means. What say the FBBO engine builders? Good idea? Cautions?
"we apply .010 - .015" of APC coating to the piston skirts to get a snug fit. After the motor is first fired up, the pistons grow and the coating abrades in areas that are too tight. Once there is room for an oil film to form, the coating stops wearing. The gage point wears the most and more coating thickness is retained elsewhere on the piston skirt....piston rock is reduced so the rings stay squarer to the bore throughout the entire four stroke cycle. Since the rings move less, they seal cylinder pressure and control oil more effectively." The APC coating is made from plastic and graphite.
Says that this technology has already been successfully used in naturally aspirated and heavy duty power adder engines in drag applications and that it only costs $30 per piston for application of a .006" typical coating thickness. They say they have different levels of hardness depending on application and the APC coating can be used for iron and aluminum blocks as well as blocks with sleeves or Nikasil coatings. No special block prep is required.
I'm a metallurgist by trade so this interests me very much, but I'm an engine builder by no means. What say the FBBO engine builders? Good idea? Cautions?
