# Swain coating piston skirts



## v8killer (Oct 19, 2002)

Hey guys,

Let's say you were to Swain coat your piston skirts for a turbo motor. In my case, I am coating the skirts of my stock 86mm GTi-R pistons. According to Dan Swain, the coating adds 0.0015" to 0.0020" to the diameter of the piston. I will then get my cylinder walls torque plate honed to match the new size of the pistons. Here is where my concern lies:

The diameter of the bore will increase by about 0.0020". To figure out how much the bore circumference increases, multiply by pi (3.141592654).

This equals 0.0063". So, the bore circumference will increase by 0.0063". This also means that my ring end gap will now start out 0.0063" wider as well. I don't have my FSM handy right now....is there enough range in acceptable ring end gaps to cover this 0.006" variance? 

Thanks for the advice,


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## Guest (Jan 1, 2003)

v8killer said:


> *Hey guys,
> 
> Let's say you were to Swain coat your piston skirts for a turbo motor. In my case, I am coating the skirts of my stock 86mm GTi-R pistons. According to Dan Swain, the coating adds 0.0015" to 0.0020" to the diameter of the piston. I will then get my cylinder walls torque plate honed to match the new size of the pistons. Here is where my concern lies:
> 
> ...


Mike suggested to set piston to wall first before coating. This is what im dong. My wall clearance it is .003 with low silica forged pistons before coating. The cast piston can be run tighter to the 10 thousandths from my understanding. I know its in the archives.


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