piston clearence and oil relief valves

[Don]

I have 2 questions..........

I am trying to understand piston to cylinder wall clearence. I have been told that a vee should have 0.004" to 0.005" clearence. Is this the difference between the inside diameter of the cylinder and the outside diameter of the piston, or is it 1/2 this difference (piston cenetered in the bore)? IE: if the difference between the two measurements is 0.004" is the piston to cylinder clearence 0.004" or 0.002"?

second question is, there are two styles of pressure reliefe valve, one plain and one with a groove. Which one is generally used?

thanks, don

[brian]

The difference is total for both sides. The measurement of the piston is made on the pin to pin axis. The grooved oil relief pistion is for bypass when cold and should be used in a full flow or external flow system.