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  #1 (permalink)  
Old 09-19-2010, 06:39 AM
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Default Weber flooding issue

This one is a little more tricky than some of the Weber stuff I have sorted out in the past. I have checked and rechecked the float level. It is 24.5 mm from the tang to the top of the carb body without that e gasket and the float is around 5mm out of the carb body at that point. I think that is pretty close. My fuel pressure is just over 2lbs. Sounds good, right?

When it is cool and just warming up, everything is good but after tuning for a few hours there is a lot of heat built up in the engine and the carbs and my fuel is boiling in the boils. The gas is running out of the auxiliary venturi with some enthusiasm! Not good. I can turn the pressure done to 1lb and it still floods on two of the carbs, one more than the other but still.

Any thoughts? (and going to a 4 barrel or fuel injection doesn't count)

Could the brass float get so hot that the air inside would be lighter, requiring even lower fuel pressure and raise the float level to the point that the fuel just rushes in?
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Old 09-19-2010, 08:03 AM
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First off I would check: Are the extra thick carb gaskets (between manifold and carb)?

It has been discussed earlier, and this seems like a very good solution. I use 2 x standard gaskets after boiling gasoline after the engine was shut dow.
(Sure boiled when running as well, but I never saw this.) In this way the carbs are better insulated from the inlet manifold.

RS
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Old 09-19-2010, 09:18 AM
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Dean:
On the 427 FE, because the Carb mountings are angled at 10 degrees it causes issues that are not inherent in a SB application. Specifically when the carb is tilted towards engine centerline 10 degrees, the opening from the main well to the auxilliary venturi is lowered (compared to being mounted vertically)causing the fuel to drip, because the fuel (although level in the float chamber) is now higher towards the inside and lower towards the outside (of the bowl). Although it is possible that you have a couple of marginally acceptable fuel valves (needle/seat) I would continue to incrementally lower the float level until the dripping stops. The heat soak can be significantly reduced with the .100 thick gaskets available from various sources.

PS: With the carb top removed immediately after this happens remove the main jet assembly and see if you can visualise the fuel passage that connects from the Auxillary venturi to the jet assy. The fuel level in the well will need to be right at the bottom of this opening (after adjusting the float level) to prevent it from it drippping and to allow the mains system to transition without hesitancy. Clear as mud?
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Old 09-19-2010, 09:46 AM
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I was hoping you guys were around today. You gotta love these Weber's! I was checking my calibration tools and I noticed that they were a little off. The float is, in fact set a little high.

Next question.

My fuel pressure seems to raise at idle, past the range of the regulator like to 5 or 6 psi. It is a mechanical pump and I was wondering if the pulses from the mechanical pump could somehow "trick" the regulator. It is also possible that the gauge is messed up. I have 3 different gauges and I have no faith in any of them.
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Old 09-19-2010, 10:12 AM
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if the fuel is pump gas that stuff is not designed for what you are doing. change the fuel.......something with a higher boiling point, i don't know if av gas would help, race gas is $$$$

insulate everything possible, fuel lines, 2x gaskets, etc.

get cool air into the engine bay, maybe some of those fancy hood vents.

sounds like you are trying to tune around a heat/fuel related problem.

i have no weber experience and this information is worth what you paid for it.....

how bout some pics just for trying?
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Old 09-19-2010, 11:31 AM
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Dean: Mine is stable at 2.5 from start, using Carter street rated (6#??) mechanical pump. If you have a fuel valve (Needle/seat) that is not sealing well when cold, (and alot of them have been faulted) then heat buildup may have some influece on it and cause it to seal better when warmed up?(?) The FE is going to be hotter under the hood, insulate the bases with the thicker gaskets and tune around the heat, no real viable way to eliminate it (?). I'd try getting the float level thing and dripping fuel issue resolved and you may find that will cure the other at the same time.
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Old 09-19-2010, 12:25 PM
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Vector, thanks for the tips. Here's a shot of the problem child!





Well, I checked the floats and they are correct now. I was sure I fixed it. The "tang" on the float was not level with the needle and seat. Due to the angle of the tang I thought it might not be closing all the way. Put it all back together, still leaking. I took it back apart, switch the needle and seat with the one next to it and it seems to be working as I adjusted the pressure back up to 2.5 -3 lbs.

I get what you are saying about the heat. I am going to order some more gaskets along with the Jaycee needle and seat assemblies. They are good to 9lbs!

Hell, I haven't even had a chance to do much with the jetting yet but that will come.
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Old 09-19-2010, 01:09 PM
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Default webers

The newer weber needle valves are junk with a large proportion leaking out of the package. You need to put a vacuum gage on them and go through a bunch to get a good set. I custom made some in order to get acceptable sealing, large enough flow size and light enough balls. Your high fuel pressure at idle will also probably be a problem.
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Old 09-19-2010, 01:17 PM
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very nice!!!!!

take your time........

since the fuel level sounds so sensitive maybe you could hook something up to put pressure on the fuel system without running the engine and then checking the level.

good luck

extra insulation might help with vibration if that could be a problem...
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Old 09-19-2010, 02:55 PM
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Well, it's all about the pressure. If the pressure is below 3, no leaks. Why in the f!@# is the pressure climbing! I have the Holley LOW pressure regulator! I am just about out of time. I'm leaving for Run and Gun Tuesday morning. Do I switch to an electric pump? Should I switch regulars? What are the other choices for a regulator? How about a return line?
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Old 09-19-2010, 03:30 PM
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i vote for the return line, regulator can't maintain the differential between the two sides.......if that makes sense. plumb a quick line for a check.
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Old 09-19-2010, 05:56 PM
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I switched to an electric pump. It worked for a few minutes then right back to 6psi, washing down those new cylinders!

I have a 3 psi bypass regulator that I might put after the carbs and run that back to the tank. That HAS to work, right? If the first regulator falters, then the bypass should bleed off any build up at the carbs.

What regulator are you Weber guys running?
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Old 09-19-2010, 06:20 PM
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I can't see what you have between the carbs as a fuel line. It looks to be metal??? I know fuel expands when it gets hot. If you are filling hot metal tube with fuel after the regulator is it possible that it is expanding, raising pressure & over filling the carbs?
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Old 09-19-2010, 06:35 PM
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Hey Hyde, how have you been my friend?

The lines on the car are the cloth classic lines from Russell. I can try the return line tomorrow. I think I have enough parts in the garage for that.
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Old 09-19-2010, 07:21 PM
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Good, Thanks. Hope all is well there!

When I changed my Y-Manifold to incorporate the fuel log it cooked my fuel. It didn't effect my pressure reading but wouldn't idle for $#&@ when it got warm. I slotted the uprights eliminating some of the heat crossover. I don't know if heat has anything to do with your problem but sounds like you have been going down the list eliminating possibilities. Also seems to make sense that pressure difference may happen after regulator. I also run a mechanical pump with a regulator but on a much smaller powerplant.
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