Alaska Cubs
Registered User
American Falls, Idaho
This very topic was discussed a while ago on the Yahoo Stinson board when discussing the the use of the improved Allen 6S122 fuel selector valve, along with a JPI Fuel Scan 450. Both neck down to 3/8" while the 165 HP Stinsons' have 1/2" fuel lines. Bob H., an A&P and retired engineer wrote:
Merry Christmas!!
Stan
I hope this helps clear things up a bit.One of the fundemental concepts in the study of viscous flow in pipes holds that: The resistance to flow caused by a restriction is proportional to the length of the restriction and inversly proportional to the cube of the diameter of the restriction. There is about 9 feet of fuel line in a Stinson 108 so changing the whole system from 3/8 in. to 1/2 in. tubing would reduce the resistance to flow by a factor of 2.4:1. Adding in 3 or 4 inches of 3/8 in. restriction only reduces the total improvement by about 4%. Hardly enough to get excited about.
Merry Christmas!!
Stan