Hi guys, i just installed a pertronix II ignitor on my mav with a 351w. I adjusted the timing to 10 degrees, i also gapped my spark plugs to .40, for some reason i tried to start up the car this morning and my Carb (holley 650) is throwing fuel from the round tube at the top, (plenty of it) it had never done that before. i tried adjusting the screws on the sides and nothing, any idea as to what could be the issue? Thanks in advance.
sounds like a coincidence that the carb problem happened after you ignition up grade. either there is debris in the needle and seat of the carb as said above or the float has failed and doesnt float any more. this is from holleys site. QUESTION How do I adjust the fuel level on my carburetor? ANSWER Setting the fuel level should be the first thing you do before attempting to make any further adjustments.The float level should put the fuel level just below the bottom of sight plug hole. You will make the adjustment with the vehicle on a level surface and the engine idling. You will first remove the sight plug, then to make your adjustment you will need to loosen the lock screw on the needle and seat. This will allow you to turn the adjusting nut to raise or lower the float level. Each hex flat on the nut will change the float level approximatly 1/32". When you have the fuel level just below sight plug hole you will then tighten the lock screw and reinstall the sight hole plug. Make sure you have a shop towel handy in case you have any fuel leaks from the Sight plug or needle and seat adjusting nut. the screw on the needle and seat is on the top of the float bowl. the screw on the top is a clamping screw, the nut turns the needle and seat. to clean the needle and seat, you need to remove the clamping screw and use the nut to unscrew the needle and seat from the bowl. clean it off with just a spray of carb cleaner and come compressed air if available. then re-install and adjust to the holley instructions. if this doesnt fix it then the float is bad and need replacement.
Thanks guys, i just removed the sight plug hole and fuel came out, i also removed the top lock screw and both needles. i just don't know how to adjust them now, with the engine idling, when will i know it's set?
One more thing, i do have a fuel regulator that reads 7psi when the engine is running, is that the right psi?
First off, the fuel pressure should be between 4 to 7 psi but no more than 7 psi. Personally I would feel better if it were 5/6 psi, but if your carb is over 3/4 years old you should really do some maintenance on it. If you are leaking fuel from one day to the next as Bryant has said, it can really only be one of 4 things, Too much fuel pressure, bad float or floats, (if your carb is old it could have the black nitrophyl plastic floats and they have been know to absorb fuel as they get older), or a bad float valve (and this could be you have dirt in the valve and it will not close properly. Here is a great site to read up and become more familar with your carb. http://www.bob2000.com/carb.htm
Thanks i got the car started. it idles kind of rough though, and it dies if i don't gas it. I'm playing with the floaters little by little and playing it by ear. the carb is literally new, i have not put no more than 20 miles on the car since i put the new motor. Idle is still inconsistent, i'm sure it's the carb but just in case here is my set up. MSD coil blaster 8 MM accel wires Plugs are gapped at .40 Pertronix ignitor II The tunning on the carb has to be the issue, i've played with the fuel mixture screws, and now the floaters. This holley carb is a pain to tune.
Holleys really CAN be a pain to tune, because there are so many tunable parts. And it is easy to start messing with it and really screw it up, so be sure to record where it was when you started, so if you get it all screwy, you can at least go back to your baseline and start over.
It almost sounds like you've got more than one issue here. You said you tried to adjust the screws on the side of the metering plates and nothing?, if you normally screw these all the way in the car will die for lack of fuel..................did you notice anything when you screw'd these in or out? If not then you may have a vacuum leak somewhere. Did you drive the car before you put the Pertronix ignitor on, and if so did the car run fine before? What tube (s) did the fuel come out of? You know, I have been fueling around with Holley carbs for a long time, and they are really pretty simple to tune.............IMHO
Need to start from square one. Remove the fuel bowls and with the bowl inverted, adjust the needle/seat til the float is level with the top of the bowl (bottom when inverted) replace the bowls, then adjust the throttle screw all the way out, then back in til it just barely opens the throttle. Screw the mixture screws all the way in (not too tight, just til they bottom out. Back them off 1 and a half turns. Start the engine and set the initial timing to 12*BTC. Adjust the idle speed screw til you get the rpms you desire (if its an auto trans, you want it to idle at the minimum it will while in gear) For a manual trans, idle it as low as possible, and still idle cold. Next adjust the mixture screws if needed, but only to the point where it gets the smoothest idle. Open the bowl sight screws and you should see fuel just barely dribble out. I'm with olerodder, the fuel pressure needs to be a tad lower, adjust the regulator with the engine running and the fuel pump working. Holleys are no harder to tune than any other carb. You just have to learn first. And once it's set, it'll stay that way for years to come. If you think you have a carb tune issue, look at the ignition first for the fix.
i think i'm starting to figure it out. I got one floater done, i'm working on the other one. As for the fuel mixture screws, they do work because i can hear the idle change as i screw them in/out. I did drive the car before i installed the pertronix ignitor, i had points, but really i had never played with the carb floaters since i installed the carburetor. I have the timing set at 10 degrees, so i hope once i get the second floater adjusted i'll have a better idea. i also think the carb was running reach, there were times where flames would come out of the carb at start up. This tuning should fix it hopefully.
