Holley running too rich

[SandbarScot]

I have a Holley 750 with a vacuum secondary on a 460 Ford / jet drive. I used to burn about 8 1/2 gallons per hour. Now I'm burning 10-12 gallons per hour and smell gas whenever I open the engine hatch. Is there an adjustment screw? I haven't changed the jets (or altitude), so they should be the right size.

[disco_charger]

Check the power valve.

[SandbarScot]

I don't have a manual. Where is it at?

[Rexone]

Power valve will be in the metering block. You have to pull the bowl. Some 750's have metering blocks on both primary and secondary, some do not. Power valve will only be present in the metering block end(s). You will need new gaskets likely too when you do this for the bowl and possibly bowl screws. Power valve has a rubber diafram which rots and then leaks. Sounds like it very could be the problem. We have all the small parts if you need. Also any local speed shop should have the stuff. Good luck :)

[SandbarScot]

Thanks. I'm heading out of town on business early Monday so it looks like I wont get to this until after OP6C. I gotta bring it in to GS for some other work anyway. I was just hoping for some majical adjustment screw to fix the problem.

[Rexone]

PV is not a big deal. Greg probably has all that stuff there to fix I'd imagine. :)

[LeE ss13]

One of the things to watch out for on a Holley is to make sure the main body of the carb where the metering plate attaches, is flat. I have seen it where they are warped and raw fuel leaks past the power valve chamber into the manifold. They will run, but the mileage is poor.

[GofastRacer]

You got that right, anytime I build a Holley, the main body automatically gets milled flat and I make sure the metering blocks are flat also!..

[Thunderbutt]

GofastRacer:
You got that right, anytime I build a Holley, the main body automatically gets milled flat and I make sure the metering blocks are flat also!.. GoFast, If you pull the bowl and the matering block and see the inprint of the holes, can you assume that they are OK? I've never had mine milled. If there is more gas leaking into the manifold would it make it idle bad?

[Hotcrusader76]

Check to see if your plastic Duracon floats are bad. They might also be causing an over-flow of fuel into the boosters.
~Ty

[GofastRacer]

Thunderbutt:
GofastRacer:
You got that right, anytime I build a Holley, the main body automatically gets milled flat and I make sure the metering blocks are flat also!.. GoFast, If you pull the bowl and the matering block and see the inprint of the holes, can you assume that they are OK? I've never had mine milled. If there is more gas leaking into the manifold would it make it idle bad? Not nessarily, you could see an imprint even if the body is warped because of the thickness of the gasket. When you tighten down the bowls, the gasket compresses and will conform to the shape of the body but may not be enough to do the job. If you take a straight edge and run it across the body, you will see the dicrepansies.
If you have an internal leak and gas is leaking into the manifold while at idle, yes it will affect how the engine idles because it's adding extra fuel OTHER than the idle cicuit. The easy way to tell is if you can turn the air adjustment screws in all the way and the motor keeps running, if it does then you have a leak somewhere!..

[SchellSchock]

heck the needle valves aren't leaking.