needle valves

[Allen Lofland]

Hey guys, I am doing the last look see on my carbs, setting floats RIGHT and
all that, and guess what. I have two different size needle valves. one 150
and the other 200. I have a set of new kits from Weber and they have two
175's in the kit, What is the right size 150-175-200 for the needle valves
dual 40 dcnf'
2 liter motor with 9.8 pistons ansa header ect Thanks

[cthargiss]

Allen, This is my baliwick! The inlet seat diameter (150=1.5mm), is used to accomodate different fuel pressures. the smaller the diameter, the higher the pressure a given set of floats can shut off. 150 inlets can shut off approx 8psi, 175-6psi, 200- 4psi, etc. All the way to 350 for gravity feed systems. If you need high feed and flow , especially for racing, the smaller size combined with a high flow pump at a higher pressure that does not exceed the shut off pressure of the inlet will give quicker refill of the float bowl and maintain a more consistant float level, ensuring consistant mixtures in extreme conditions. Note: too low a pressure for a given inlet will not allow suficient fill recovery in high demand situations, same as too low a fuel pressure regulator setting on stock carbs. A common mistake I have seen on too many cars. Hope this helps, Craig