Re: Too much fuel pressure?
what kind of carb, rochester or holley?
flooding is caused by the needle valve not closing and stopping fuel flow. what you can do is pull the carb off, turn it upside down to get most of the gas out of it. Turn it right side up and blow into the fuel inlet of the carb, you should be able to and be able to hear air going into it. Then blow into it while turning it upside down, the float should drop (upside down) and close the needle valve and you should not be able to blow in or hear anything. Blow as hard as you can, if air goes in then you have a bad needle valve and you need to replace it.
But if this proves the needle valve is good it doesn't mean the float is. New floats are not part of a typical rebuild kit, you almost always have to buy them separate and if someone else rebuilds your carb floats are almost always not replaced unless you specifically ask. The float could be leaking and not closing the needle valve, or the float level could simply be set wrong. Not all floats float at the same level so following a carb rebuild instruction sheet and setting float level at x inches does not always work. If it's a 1975 carb then I wouldn't be surprised if you need new floats. And if it's flooding the idle mix screws aren't going to affect anything. You'll need to get the needle valve working and make sure the float is good and set at the correct level before the idle mix screws have any chance of working.
With the float, remove it and shake it. if there's fuel inside it it's bad. And you can also submerge it in a cup of gas and watch for air bubbles and also make sure it floats. also note if it's a metal or plastic float. It's UNcommon for 30 year old metal floats to be working!
very unlikely the fuel pump is pumping too much, as in too much pressure. All carbs require a couple psi pressure minimum to function and less than around 10psi. Once around 10psi and higher the pressure gets too great and the needle valve can't maintain a steady fuel level in the carb. General rule of thumb is 3-6 psi at the carb. You'll usually see 5-8 psi from a good mechanical fuel pump at idle but at high rpms that pressure will drop which is normal. Rigging up a pressure gauge to see fuel pressure when the motor is running is not always easy. First step would be to just check pressure directly from fuel pump into handheld gauge while cranking the motor. You should see at least 3-4 psi but can see up to around 10 psi. Up to 10 is normal because it's just a static pressure test with nothing flowing so don't get misled. If it's higher than the traditional 3-6 psi then all that really means is you should check fuel pressure with motor running to get a correct fuel pump pressure reading.
