Post by noser23x on Sept 5, 2023 6:34:19 GMT -5
I have a 4412 carb on a fairly stock vortec 350. I can't seem to get running perfect. It will idle good but it won't take the fuel when I hammer on it unless I peddle it a couple times. It runs very rich. The plugs are black. It has 68 jets in it and a 4.5 power valve. Ive tried the timing everywhere from 32 to 38 total. I have tried to set the float level but the engine is tilted to the passenger side in the car. Could that maybe be the problem? Accelerator pump need adjusting? Different size jets? Suggestions?
68 is a decent starting point with a jet on a mostly stock vortec, power valve requires taking a vacuum reading at idle and dividing by 2 to get in the ball park of the power valve size. If the power valve was too large (which in your situation I don't think is the case) it will dump more fuel in. Too small and you will run into a lean condition. Power Valve is part of the enrichment circuit, under heavy load manifold pressure will drop allowing allowing the valve to open and additional fuel to supplement the jets.
I would start by making sure the accelerator linkage is set correctly and you don't have any vacuum leaks. Along with that, replace plugs and get timing to a place the engine is happy.
If none of those are an issue, it sounds like something in the accelerator circuit. Discharge nozzle is a very easy swap out and probably where I would investigate first. Different nozzles disperse fuel differently, whether it be a more aggressive dump of fuel or a more prolonged squirt. Accelerator circuit consist of the cam on the linkage, accelerator pump itself, and discharge nozzle more or less. Different cams on linkage change the curve of how the fuel comes out, Different size accelerator pumps change the volume of fuel, and the discharge nozzle is how that volume of fuel enters the carb.