I have a 500 Eldebrock 4 barrel carb on my 305, its running to rich and I thought I would adjust the carb pump to see if that helps before changing the jets. I carb pump adjustment rod has three holes for adjustment, which hole would make it run leaner, the bottom or the top hole. thanks
The accelerator pump is to give a single squirt of fuel each time you press the gas pedal but not on steady cruising so it really has no direct effect on running rich. Assuming there are no vacuum leaks or other problems causing your rich condition the typical place to start tuning is with the metering rods. The metering rods have tapered tips that fit inside the jets essentially changing the size of the jet depending on engine vacuum. High vacuum pulls the tapered metering rod deeper in the jet making it flow less fuel. During low vacuum a spring lifts the tapered metering rod out of the jet essentially making it larger. The Edelbrock 500 is a copy of the Carter AFB and is reasonably easy to tune as the metering system can be worked on without removing the carb.
Thanks guys, idle mixture adjustments have been made, so I am assuming metering rods, the book I got with the carb does not not tell me the size of the rods that are in it, is there a number on the rods that would tell me, as it is puking black smoke I guess u guys it right on, thanks brent
If it's puking black smoke there is probably something wrong with it. The first thing to check is the power valve piston that controls the metering rods. They sometimes stick and when they do they are normally stuck in the full rich position. There are two covers on the top of the carb each held on with one small screw, these cover the metering rods/power valve assemblys. With the cover removed the piston should be spring loaded meaning if you gently press down on it it should spring back up. As soon as the engine starts engine vacuum should pull them down. Up is rich, down is lean. Otherwise you might have a problem with leaking needle/seats or floats that are out of adjustment or defective.
What kind of fuel pump are you using ? These carbs don't take much fuel pressure so you may need a pressure regulator even if you are running a High output mechanical pump. Also check your float settings
Edelbrocks are renown for being able to be bolted on right out of the box without touching a screw and run fine. Why not call the tech line at Edelbrock first befor monkeying around with this.
