I Rebuilt my Carb and Now it runs worse....

[MercuryMarc]

Sorry for so many posts- I am getting my new 200 fixed up as my current 200 is slowly dwindling....
I have a Holley 1940 1bbl carb on my 69 200 six cylinder motor.
So I saw gas seeping out of my carb and onto the intake manifold - hard to tell where, but it was not from the fuel line junction, sort of from the middle of the carb body all over, looked like the center gasket. So I rebuilt the carb following the directions (and had no leftover parts....).
I did find a piece of foam debris between the fuel line filter and the fuel inlet valve (maybe that was causing my backfiring on hills).
Now the car runs worse- starts up like a champ, good visible squirt of fuel down the carb throat when I push the throttle linkage, accelerates briskly if I jam the accelator, but hesitates and stalls if I slowly depress the accelerator.
I have a manual choke and runs OK if I leave the choke partially closed, but problems return if choke plate 100% open. All this with the car warmed up to operating temperature.

Appreciate any advice!

Marc in SF
63 Comet
Dwindling 69 200 current engine
Rebuilding my 78 200 block
http://mercurycomet.net

 

[MercuryMarc]

I stopped by the carb shop and the guy at the counter thinks it is most likely a clogged passage- he suggests that I take it apart again and use compressed air to clear the passages. So that's the plan for now. The "compressed air" in my garage is basically me blowing into a length of vacuum hose and pointing it in the general direction of my carb, let's see how that works.... 8)

 

[pedal2themetal45]

HMM HI
Did you try readjusting the A/F mixture when it was up to temp.. If you just went by the book you might just need to fine tune it.. If you have to run it with the choke on a little bit you might need to turn the mixture screw out a little bit to make it richer..
Tim

 

[MustangSix]

Marc, I've done that many times. Fixed things until they do not work at all!

It sounds like the main circuit is clogged. There is a jet in the bottom of the carb bowl. Take the lid off and squirt carb cleaner thru that hole and you should be ok.

 

[pedal2themetal45]

OH
Also is the idle RPM up high enouff. Pulling the choke on would bring the idle RPM up also..
Tim

 

[MercuryMarc]

Thanks Jack and Tim!

 

[MercuryMarc]

Woo Hoo!!!
I removed the top of the carb, removed all the fuel with a syringe, then removed the float. Then I removed the main jet, power valve and jet, accelerator pump rod and ball, and the idle needle valve. I shot carb cleaner into the passages, then blew out all the holes with compressed air. Actually I had a length of vacuum hose, cleaned off one end (and labeled it so I would not suck on the fuel soaked end...), and blew into it. This really provided plenty of force as carb cleaner shot up from the main circuit onto the undersurface of my hood! I aimed the end of the tube and blew into all passages and then reassembled it again. Tonight I took the ol' Comet out for a spin. Ran great! No more hesitation. I did not get a chance to tune it since it is raining but just used 2.5 turns on the idle mixture screw. Will perfect it this weekend.
Thanks again for all the help!
Marc

 

[pedal2themetal45]

HI MARC
Glad you got it going..
Tim