This: 3 posts ^^^^^^^ above!
Stan is 150% on the money here. Fuel pressure is crucial for Webers and Dells but ESPECIALLY so for Solexes and Kadrons. 1.5 psi may be too high. The only way to get it right is to run the engine with a gauge T'd into it. If mechanical, stack up the gaskets. It's hokey, but it works. I had eight gaskets on one I did to get it low enough, and it was still 1.75 psi.
If the pump is electric, an aftermarket regulator needs to be used. Same procedure, but adjust the regulator until you get the right reading. The regulator "settings" are known to be VERY inaccurate to actual pressure.
Needle seats are notorius for leaking on the single throat carbs.
Great post Stan!
P.S. I get 32 mpg on Carlisle trips ripping along at 65 to 110, but usually sitting at 75-80. I have 180 hp and Weber 44 IDF. The car is tuned, synched and jetted properly.
10 mpg is PIG rich and is emptying your wallet and filling your crankcase with gasoline-washed oil. BAD!