[G.M.]

Had some time this morning and put the Airtex fuel valve on the 39. I took off the return line needle valve so the only restriction in the return line is the little over 1 lb fuel check valve and the .130 ID of the line. If larger return tube is used one of the fittings will to have about a .125 orfice.to restrict the amount of fuel returned. So now all I have is a "T" in the carb line, the fuel check valve and the 3/16" OD return line which is steel brake line. I started it up and the fuel pressure at about 350 to 375 RPMs idle is 1.5 lbs.
Speed the engine up to 450 to 475 and fuel pressure go's to 2.5 lbs. This is lower fuel pressure because a good potion of the fuel is being returned to the tank. Without the return the pressure was 3.5. Let the engine warm up to about 160 and checked the temperature of the gas tank which was 77 degrees so we will assume the fuel was 77 degrees. At 160 engine temp I checked the top of the fuel pump, 95 at the top and 126 at the bottom. Checked the fuel bowl on the carb, 85 and the intake manifold below the carb, 158. This is something I forgot about, the cool fuel cooling the carb.
Wouldn't get over 175 degrees as it was only 75 outside. I put the fender cover over the radiator and left it run about 20 minutes and got it up to 210 degrees at the bottom of the top radiator tank. Top of fuel pump now read 93 and bottom of pump was 126. carb was 84 at the fuel bowl and 172 on the intake flange. I still have the fuel sight glass on the carb so I can watch the fuel level in the carb. I shut the engine down, closed the hood and tomorrow I will see where the fuel level is in the carb.
This looks better than I thought it would. NO MORE VAPOR LOCK. G.M.