AlwaysBroke Posted September 24, 2008 Share Posted September 24, 2008 I have a Demon carb, and this morning fuel was DUMPING out both my secondary boosters. It was not my float because the bowl was completely dry. (Dumping out so fast that the bowl couldn't even fill up) Does anyone know what this could be? My first guess was that jets unscrewed and fell out, unlikely but ok. I took the whole thing apart and I cannot find one thing wrong with it, except one stud was broken off. I doubt that it had anything to do with it as the seals were super tight. Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted September 24, 2008 Share Posted September 24, 2008 The needle seat probably has trash in it. Need to pull out and blow air in it and also use some carb cleaner on it. It it is blocked and can not seat then fuel will come out at the top of the carb. You can also check your power valve to make sure they are not busted, they are inexspensive to replace. Probably a good time to rebuild the carb. Holley parts will work in the barry grant. John I have a Demon carb, and this morning fuel was DUMPING out both my secondary boosters. It was not my float because the bowl was completely dry. (Dumping out so fast that the bowl couldn't even fill up) Does anyone know what this could be? My first guess was that jets unscrewed and fell out, unlikely but ok. I took the whole thing apart and I cannot find one thing wrong with it, except one stud was broken off. I doubt that it had anything to do with it as the seals were super tight. Quote Link to comment Share on other sites More sharing options...
AlwaysBroke Posted September 25, 2008 Author Share Posted September 25, 2008 I dont think its the seat because the bowl was dry so it never even had a chance to seat. Im still learning about this kind of carb so what does the power valve do and how can I check it? I called Barry grant and they basically just called me an idiot and said that this carb wont work on my motor and they dont know what im talking about. Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted September 25, 2008 Share Posted September 25, 2008 I'm not sure then. The fuel enters the needle seat and then into the bowl, as the fuel level rises it raises the float which will close the needleing seat which stops the flow of fuel. So if the fuel bowl is dry then no fuel is entering in. The power valve has a diaphram also. It could be torn allowing fuel to go from the bowl into the metering block into the venturies and flooding. You need to use a vacuum pump to check a power valve. They also have diffirent sizes so make sure you find the number on yours and get one with the same. Example if you have a 4.5 power valve then you need to be pulling at least 6 inches of vacuum from the engine. If you drop below 4.5 then it will open and will be to rich. I hope this helps, and I know what you are talking about concerning Barry Grant. They also told me my blower carbs would not work with the camshaft I was running and boy were they wrong..... I do not have that worry anymore. John Quote Link to comment Share on other sites More sharing options...
AlwaysBroke Posted September 25, 2008 Author Share Posted September 25, 2008 ok thanks. i will go ahead and replace the valve tonight while i already have it apart. is there anyway to reduce the amount of vacuum its pulling? I think it might have too much and its causing the vacuum advance to break. Also has anyone ever worked with a carb on one of these motors? I really want this carb to work but I need a starting point, im running around in the dark. Quote Link to comment Share on other sites More sharing options...
jasonZ Posted September 26, 2008 Share Posted September 26, 2008 John is right. For some reason or another there is way too much fuel in the bowl. This can be caused by a stuck needle and seat, improper float level, or even too much fuel pressure. Fuel can't get to the boosters without going into the bowl first. How big is your carb and what is the rest of the combo? I know the guys at BG are not the most helpful but I have been able to get a few good answers from them over the years. I'm sure they think the carb might be wrong for the application (which may be right) and don't want to waste time helping you make it work. Hope this helped a bit. Jason Quote Link to comment Share on other sites More sharing options...
AlwaysBroke Posted September 26, 2008 Author Share Posted September 26, 2008 Im gonna put it back together and see what happens. It is possible that the fuel was all the way at the top, although I was certain (now Im starting to wonder) that I saw the top of the float in the sight glass. BG said that was entirely to large and that they didn't even make something small enough. But there has to be a way to make it at least bearable until I can save up to get something else, and BG would not even give me a hint. What carbs are you guys running nowadays? Is Holley still the reigning champ? Quote Link to comment Share on other sites More sharing options...
jt1 Posted September 26, 2008 Share Posted September 26, 2008 It's a long shot, but are you sure your float "floats"? I've seen one that appeared to be ok, but if you dropped it in a cup of gas, it would go right to the bottom. It was flooding the heck out of the motor too. A 390 Holley would probably be about right for the 4.3 in your sig. jt Quote Link to comment Share on other sites More sharing options...
AlwaysBroke Posted October 5, 2008 Author Share Posted October 5, 2008 Update, I put it back together and it runs great now, the best its run since I built it even with no vacuum advance. Im not sure exactly what was wrong but it was probably the obvious and had something in the seat. I also noticed that the holes, in the body for the power valve, had a chunk of metal, from drilling the hole, slightly in the way. Im not sure if it has anything to do with it running better but its the only abnormality I saw. Quote Link to comment Share on other sites More sharing options...
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