Carb Flooding on 200" Six

[jjohnston]

Just completed installation of a 200" six and C4 in our '63 Futura. I'm having trouble with carb(s) flooding at idle. Both the 144", manual choke, and the 200" auto choke do the same thing. Engines starts fine and then fuel starts running out everywhere. Almost seems like the fuel pressure (new fuel pump) is too much for the float/needle & seat. (Most new pumps output are 5.5 psi min to 7.0 psi max). Seems to me that 3.0 to 3.5 min should be enough. Any experience out there with this? THANK YOU.

 

[JackFish]

I'd suggest a stuck or damaged needle valve.
Might need a float adjustment too as they work together.

 

[powerband]

... If you already replaced the carb needle&seat, adding inline filters before and/or after the pump can add confidence that even minor tank or line sediment doesn't add to flooding problems. Pump pressure at idle or above should not unseat a typical OEM type carb. Holley/Weber's type 2bbl's are recommended to have a FP regulator.


. .

I had the Dial type "Mr Gasket" regulator rupture and spew fuel pump loose at full pressure ... now I use sealed type...

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have fun

 

[wsa111]

Clamp the fuel inlet hose to the fuel pump. Try to start the engine & run it out of fuel which is in the fuel bowl.
this allows the float to lower completely. Remove clamp on fuel pump inlet & start the engine, sometime if debris is causing the needle valve not to seat the sudden rush of fuel will hopefully dislodge it if that is the problem.
Otherwise you better pull the carb apart & find the problem.
Is the carb an autolite 1100??

 

[jjohnston]

wsa111 - yes both of the carbs are Autolite 1100's.

 

[wsa111]

I have seen where new fuel pumps have close to 7# psi.
I missed the point that the problem exists on both carbs.
Just install a pressure regulator & set it to 4# psi area. That should do the trick. Bill

 

[xctasy]

I have seen where new fuel pumps have close to 7# psi.
I missed the point that the problem exists on both carbs.
Just install a pressure regulator & set it to 4# psi area. That should do the trick. Bill

A normal factory 144 to 200 cubic inch 1-bbl carb shouldn't ever need pressure regulating. However, some fuel pumps are off the shelf designs which may be based on V8 pumps, and have significantly more flow and pressure than the original.


I'm with Bill, if you've struck out twice, your third option is to limit fuel pressure, but you shouldn't have to if the carbs are the 100% American designs.


That's it. One thing. With white box supplier outsourcing the way it is, some replacement fuel pumps might be on the upper edge of original fuel pressure and flow specification. Bill has always said if its a traditional US Holley (US Autolite/Motorcraft 1-bbl or 2-bbl) then good fuel pressure is important. His rationale is that's how the US engineers did it, why limit pressure? I respect that point of view. I personally believe (based on two separate sources) that winding down pressure without flow restriction takes the load of the needle and seat, and allows finer control of float level, and thats based on fuel consumption GM and the Vizard company APT did on carburettor rough road simulators. (That's of little relevance to us here, but its why I recommend the lowest pressure that still allows the float and seat to work properly. Bill has always said in his experience, he wouldn't start limiting fuel pressure ever on a US carb.)

Normally, leaking is ALWAYS a foreign Holley/Weber 2-bbl 5200 to 6500 kind of thing, and also a down draft Solex/Zenith and Weber import 1-bbl kind of thing. On those, you just take the fuel pressure down to 3.5 psi max with a regulator that doesn't take out the fuel flow. Solex/Pierburg carbs (downdraft 1 and 2-bbl import carbs found on Opels, Volvos and some other Europeans vehicles) also suffer from this. I had a 78 hp 1958 2.3 liter Vauxhall with a Zenith 34VNT that leaked fuel all the time unless the Malapasi inline fuel pressure regulator was fitted, and the fuel pressure wound down to 3 psi. Typical of the utter crap that the English and Europeans got away with forcing on the non American world for over 50 years. Thankfully, proper American designed carbs are always designed to take a bit of pressure, leaking fuel is always a foreign carb problem.


A point of note. Sometimes, the leak is the upstream flare into the carb, and its seen as a carb leak.


See this post.



http://vb.foureyedpride.com/showthread. ... -new-parts

It definitely has issues. Any little imperfection will make it leak. Maybe a honing stone in the shape of a cone like a dremel or drill type may reshape it. Honestly with all the time you've spent on it, you could bent a new one. Just cut the end off and reflare and see if it works. That one is bad at the 11 o clock position plus the ridges all the way around.

 

[wsa111]

X, i recently installed a Carter mechanical replacement & the fuel pressure was 7 1/2#
That prompted me to install a regulator for my Holley. With the Holley i set it at 5#.
No problems since.
The Holley could handle the pressure, but it all depended which float you had in your Holley.
Good move 5# works perfect.