Valve sizes

[Anonymous]

Hey,

Are the XF valve sizes 1.80 inlet, 1.5 exhaust, or 1.84 inlet and 1.5 or 1.49 exhaust. I am looking at putting these sized valves into an xe alloy head because i have heard they are slightly bigger, and then put the head onto my XD 250 block. I am looking at using a holley 390 4 barrel with vacuum secondaries and a mild cam (like the 14771 from crow cams) and 9.5 compression. Would bigger valve sizes again be appropriate, like 1.9 or something.

PS I don't wanna lose too much low down power.

 

[xctasy]

The XF valves are about 1.8 and 1.5" respectively. They are best with the earlier XD 1/2, XE Alloy Head cylinder head, which has no high swirl chamber.

High swirl, or mixture motion, is a very important tool in the last XF heads for getting good ecomomy, emmisions and power. But it sacrifices peak power and gains it back by using a tighter ignition controlling system and semi feedback control on the unleaded engines. On an LPG or Holley carbed engine, this is not what you need.