Having trouble finding the cause of overly rich idle/low speed. I'm almost at my wits end trying to solve this problem. The carb has been thoroughly cleaned, all orifices are clear and new gaskets etc. The power valve is free to work and does not leak, the seal on the cover is tight, and the vacuum passage is clear. The floats are are set right and the fuel level is right. When this carb was first installed it ran fine,idled fine? What in the world can literally happen overnight? I wonder about the seal at the base but don't have a clue how this could change. I'm using a gasket that completely covers the bottom of the carb and the carb is mounted on a flat 4 hole Ford spacer.
Any ideas?
I installed a fresh 4150 Holley ('57 Ford) and it runs flawlessly so there must be some quirk i'm overlooking.

......got past the fuel filter and clogged an orifice

Ed Jenkins

Ford Galaxie Club of America member #3350
1966 Galaxie 500 Convertible built in Chicago Illinois, will have a stroker 390( 429 cid?). 780 Holley?, built C6, Crites Aluminum radiator, and a rust free frame from the south. Work continues.

Please visit and revisit the Carb Forum athttp://network54.com/forum/88781

Here's a quick test you can try. Turn the idle mixture screws all the way in, but don't tighten them, just bottom them. Does the engine still run? If so you may have done what I did when I rebuilt mine... in the semi dark (in a hurry). I had the top gasket flipped upside down which, at first glance looks just fine. But if you look at the area where the air cleaner bolt goes through you'll see a semicircle air bleed. In my case the gasket didn't cover the semicircle all the way so it was sucking gas from the primary bowl through that air bleed! Flipped the gasket the right way, good to go, perfect in fact :)

Good luck and post back here.

Cliff

Thanks for the responses. Yes, the idle screws are totally ineffective. The top gasket was in place also. all orifices seem to be clear. removed the nozzle blocks and they both seemed flat on the sealing surface ( no warpage). They had both been off a couple of times so it's possible there was a leak at the junction between the nozzle block and the carburetor body altho I didn't notice any. They were both very tight so that doesn't seem likely but at this point I'll try anything. Installed some new gaskets. The anti-syphon bleed holes in the nozzle blocks were also clear along with the small orifices above the throttle plates. I realize that to set the mixture screws the throttle plates need to be nearly closed and that's how I first set it up and it idled so good. I'm going to give it another try tomorrow and I'll be very surprised if changing those nozzle block gaskets do the trick but who knows?

Dee I'm tellin' ya, really LOOK at the top gasket. It's easy to get upside down. Impossible to put on backwards but easy upside down. Flip the top cover over, place the gasket and you'll see what I mean.

There's only a few ways that it will idle with the screws all the way in.
1) misinstalled cover gasket as I've mentioned.
2) sunk or misadjusted floats
3) throttle plates, primary OR secondary, open too far at idle.

I've seen #3 as a problem before on a friends carb. The set screw was adjusted too far in which opened the secondary plates too far which then caused enough vacuum to suck gas through the unchecked secondary nozzles. But it's not common for folks to mess around with that adjustment so not as common as a flipped top gasket :)
Good luck and happy hunting!

Cliff

Problem solved. I should have taken a good look at the the nozzle blocks! I installed the wrong set...these had much larger idle orifices and are evidently used in "emissions" carbs with secondary air bleeds? After re-adjusting the secondary throttle plates ( for a better non-sticking fit) and installing the correct nozzle blocks with the small orifice idling tube the carb runs like it suppose to.

You don't mean the boosters, do you?

Yes, the Booster assembly(s). Pardon my jargon.