I have a holley carb part number 4777. It has a hard time starting and it will idle for about 10 seconds then it will start dripping fuel into the carb and then you can see the fuel just running into the carb then it idles rough and cuts off. It does great if I keep the rpms up. I'm thinking its a blown power valve but if it was that wouldn't it idle rough and flood out imediately? Any help would be greatly appreciated.

 

Change the o-ring for the needle and seat first. If it leaks, the float can't stop the flow of fuel into the bowl and the extra fuel will leak out the boosters causing it to flood. The power valve circuit doesn't flow any fuel when at an idle.

 

I'm not that familiar with holley carbs, what/where is the needle and seat?

 

ok I looked it up and know what you're talking about, I'll try that in the morning. Thanks

 

It's usually just dirt in the needle/seat. But sometimes you won't see trash when you pull needle assembly up cause it gets washed out as you pull needle assembly up and float pressure no longer keeps it trapped.

 

Hi, if the other suggestions fail to solve your problem try adjusting the floats, this can be done with a wrench and a screwdriver, remove the sight plug on the carb bowls and see if fuel sloshes out when you start the engine, If so loosen the lock screw on top of the carb bowl and turn the adjusting nut till fuel is just about level with the sight plug hole. Also if you are running a performance fuel pump elect. or mech., you may have to use a fuel pressure regulator and adjust the pressure to 5-6 pounds to prevent the floats from bending due to too much fuel pressure, good luck.

 

i replaced the power valve, oring on the needle and new metering block and fuel bowl gaskets, adjusted the floats and the air fuel mixture screws and its running like a dream.

 

Amazing what a bit of maintanence can do. Glad to hear a good update.

You hear so many horror stories about people buying old Holleys like a 3310 and expect it to work like new. Some of the old carbs just need a real good rebuild, not just a gasket change. Other old carbs are only good for parts.

I have to maintain 2 old 850 DP running on alcohol. I've done a complete rebuild on them and they're like new now including using Eastwood's Holley carb paint to make them look good. Keeping the seals and o-rings from drying out is the hardest part. I keep many spare parts so I can do emergency repairs at the track if I have to. Needle and seat o-rings on alcohol don't last long. That's why I suggested it as a fix. I've seen mine flood out too many times from the same thing.