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Holley 750CFM DP #4779 Flooding Issue Rear Bowls
Took my car out today and during the run I gave it a few hard runs through the gears. On my last run it starting trying to cut out on me and die and I had to nurse it back to the house. I Barely made it as it refused to idle and I had to keep reving it to keep it from stalling out. Once I got back I could smell it was a fuel issue. Took a look at the carb and I can turn on the electric fuel pump and the fuel starts poruring into the rear bowls. The linkage is fine and the butterflies are closed. It seems there is something wrong on the back end of the carb as the front is dry as a bone. Any suggestions where to start? I am gonna pull it tomorrow as Im somewhat familiar with Holley carbs and know just enough to probably get me in trouble. : )
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Don't pull anything - just replace the needle and seat. You can do it from the top of the bowl with the carb on the engine. It's a ten minute job. Then just set your float level below the sight plug. Sometimes secondaries need to be set a little lower, especially if your carb is tilted.
The reason a lot of Holley guys with big engines have to set the secondaries a little lower is because the gas today percolates out a lot easier. Go ahead and set it to the bottom of the sight plug, then take it for a nice hard run, pull in the driveway, and take the air cleaner off. Then watch the secondaries and see if it's boiling out through the boosters. A little can be ok, a lot is not. |
Copy ..... thanks for the help!!! I’ll give it a go tomorrow. Seems strange as this is a new carb with only 500 miles on it. Is this a common issue or maybe some trash got in there?
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Fairly common issue, a very small piece of debris is all it takes to prevent the needle from sealing. In fact, by the time you take the needle assembly out and inspect it, the debris will have fallen out. You will then deduce it as a bad needle, which in my experience is rare.
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A speck of crap stuck in there, a sticky N/S, happens all the time. You probably have Moraine filters, which are just big tubes of brash mesh, at the fuel intake fittings on each bowl. They work pretty well in conjunction with another filter back along the line somewhere. I have mine back by the fuel tank. First just go ahead and replace the N/S and get the car running again. Then, over the winter, pop the fuel bowls off and inspect the bowls and metering blocks for crap, zinc flaking, etc. Take out the Moraine filters and springs too and see if they've got any chunks of black rubber flecks or anything else in there.
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Since nobody else has asked, how about the engine specs. I ask, as the carb might be too much for the engine you have in your car,which may or may not also compound the issues you are currently having.
Bill S |
Bill,
Is a Southern Automotive 427 SO stroked to a 482. |
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Ok...removed needle and found a small piece of loose black rubber on the plunger that was making it stick. I removed it and and cleaned the needle. I then reassembled it and set the float level. Turned on the electric pump and it held. Everything seemd fine.
I then went to start it and the starter just goes thunk.....like the engine is locked up. You can feel the engine trying to turn so it’s not the starter. It turned over fine yesterday on my return when I was trying to figure out the issue. I’ve also accounted for all my parts so no way something feel into the bowl and got into the engine. Air cleaner nut - check Air cleaner nut washer - check Both needle assy gaskets - check Needle adjustment nut and screw - check Tools used - check Cant imagine anything fell into the bowl unless I’m missing a part I’m unaware of but can’t imagine what else could make the engine lock up. |
OK, remove a few spark plugs, put a socket on the crank bolt, and make sure you can easily turn the engine by hand.
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... and make sure you're not in gear.:D
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Clockwise or counter clock wise looking at the engine from the front? A spark plug from each side? Or does it matter
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On the positive note... she runs great!!! Thanks for all the help. You were spot on on the issue and again I learned something new. E5 |
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Thanks!!! Give me a few days to rebuild my testosterone back up : )
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Comments
1. I ALWAYS carry a 5/8 open end and a flat screw driver to address this issue if it happens on the road...it's a trivial fix, count the turns coming out and do the same going in...easier with sight glass bowls like an HP has.
2. For turning over the motor I bought a ratcheting breaker bar which makes spark plug removal unnecessary...lots of torque Semper FI |
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