The Stovebolt Site Forums The Shop Area Engine Shop hello all 1904 holley jet question?

I have a 1904 holley on my 261 its good at half to full throttle but it sucks at idle and hesitates when you push the foot feed. The acc pump is working
but im wondering about the jetting and the power valve. its from a 223 f**d but is very good in the upper rpm range. thanks Chris

I run 1904 Holleys on several 235's with excellent results.The main jet in those carbs is normally a number 65,same as newer Holley 4bbl jets.Check out the power valve operation,you need base gasket with a notch in it so engine vacuum can reach the power valve signal port.

Hey i did cut my gasket and it runs much better now.
Im still thinking ive got some other issue cause i just cant get it to idle right. Its a rebuilt carb i got at advance then slightly opened the holes to fit my manifold. Im wondering if i need a different power valve if so how do you decide which one also maybe a larger.

The main jet won't affect the idle quality ,but if the power valve is open during part throttle or idle,the engine will run quite rich.
Remove the power valve cover on top of the float bowl,carefully remove the rubber diaphram,look inside,you can see the gas level,should be about 3/8 to half an inch down as a crude guideline.You'll see a small port next to one of the 3 screw holes for the power valve cover,plug it temporarily .Now start the engine,but be careful,if the float level is too high or the float needle defective,gas will pour out.With the engine idling,unplug the port,the idle should increase in speed if the vacuum signal is present.If ok, then increase the engine speed to a fast idle,stick a pencil down the power valve opening and gently press down the power valve jet needle,Use a flash light to see what goes on.The engine should run rough from an enriched mixture.If all that checks out,and the engine still has a poor idle ,must be a vacuum leak or crud in the idle restriction jet.