Forged Pistons , Ring end gap & Piston clearance by Arias

Minimum Ring End Gaps And Clearance

Ring	Application	Minimum End Gap Per Inch Of Bore
Premium Top Rings	Blown Fuel, Alky, Gas	0.008
	Injected Fuel	0.007
	Blown Fuel, Alky, Gas	0.0075
	Blown Gas, Street	0.0065
	Nitrous Less 250hp	0.0065
	Heavy Nitrous 250hp+	0.0075
	Na Alky, Gas	0.0055
	N.a Gas, Street	0.005
Cast Iron Second Rings	Blown Fuel, Alky, Gas	0.006
	Na Alky, Fuel	0.005
	Na Gas	0.004
Third Groove Oil Control Rings	Upper And Lower Rails	.015"  min.

Recommended Piston Clearances

Minimum Piston To Valve	Normally Aspirated	Int. 090"   Exh. .110"
	Blown	Int. .125"  Exh. .175"
Minimum Piston To Head	Steel Rods	.040"-.050"

Source : http://ariaspistons.com/technical.asp