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Trying to diagnose pig-fat rich idle condition on 2bbl Holley

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Trying to diagnose pig-fat rich idle condition on 2bbl Holley

Old 08-05-2013, 11:02 AM
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Default Trying to diagnose pig-fat rich idle condition on 2bbl Holley

This is not a performance boat application, but the boat does run one of the 2300 series Holley 2bbl carbs which are very similar to some of the 4160 series side-hung float Holleys, so I thought I would ask for some input. Boat is a bow rider that belongs to a friend, with an early 90's OMC with a 302 Ford V8 and the aforementioned Holley 2bbl. Boat would run OK cruising and full throttle, but did not idle well - wanted to load up, stall, and surge. I borrowed the boat for a weekend while mine was down, and tried to fix some of the nagging things that were wrong with it as an offer of thanks to the buddy who lent it to me. I thought a basic rebuild and kit install would take care of the poor idle problem. Boy was I wrong. I put in a Holley renew kit after soaking the parts in carb cleaner and thoroughly blowing everything out. Checked all the surfaces for warpage with a straight edge and all looked good. Put it back together, and now it runs worse! Absolutely will not idle, runs pig-fat with black smoke belching out and fuel dripping out of the boosters.

Float is internal adjustment on this carb, so I pulled the float bowl, installed a new float, and set the level a bit on the conservative side to rule out a float issue. Needle and seat are also new, along with a new 5-0 power valve. Reinstalled the bowl with the new float, and no change. Still have fuel running out of the boosters. Thinking that I may have a bad power valve out of the box, I installed the old one - no change. Tried idle mixture screws, not really any difference there either.

At this point I wanted to rule out an ignition problem, so I checked timing. Rotating the distributor to an extreme advance to extreme retard at idle did not affect the idle very much - still crappy. Checked cap and rotor, and they looked clean.

At this point I am suspecting a vacuum leak somewhere that is causing the carb to think it is under part throttle operation resulting in the power valve kicking in and send fuel through the power circuit into the boosters. Thinking about blocking off the PV to rule that out alltogether. Also thinking about removing the electric choke and temporarily blocking off the vacuum port for the choke pulloff to eliminate this as a source of a vacuum leak. I had a new carb gasket on there, so i doubt that is the issue.

Anything I may have forgotten? Anyone have any suggestions on any other things to check? I wish I had a known good Holley 2300 2-bbl to throw on there to rule out the carb as the issue.

thanks in advance!
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Old 08-05-2013, 12:55 PM
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is sounds like the fuel pressure might have gotten to high,does the engine have an electric fuel pump?
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Old 08-05-2013, 01:14 PM
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No Mike, it's mechanical. Thanks.
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Old 08-06-2013, 08:27 AM
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last year i put a holley 4 bbl carb and a new mechanical fuel pump on a friend,s 350 sbc in his car,thing ran like chit,blubbering fuel and black smoke,everything in the carb was good so i installed a fuel pressure gage,this stock fuel pump that was valved at 5.5 lbs was making 13 lbs so i took it back and exchanged it for another one and it runs great at 5.5 lbs pressure.moral of this story is,anything can happen with a mechanical pump!
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Old 08-06-2013, 09:06 AM
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Originally Posted by mike tkach
last year i put a holley 4 bbl carb and a new mechanical fuel pump on a friend,s 350 sbc in his car,thing ran like chit,blubbering fuel and black smoke,everything in the carb was good so i installed a fuel pressure gage,this stock fuel pump that was valved at 5.5 lbs was making 13 lbs so i took it back and exchanged it for another one and it runs great at 5.5 lbs pressure.moral of this story is,anything can happen with a mechanical pump!
I hear you on that, Mike. How do you install a gauge with the metal fuel lines in place? Thing is, nothing was changed with the pump, but I guess it is possible that the new needle and seat is less tolerant of fuel pressure than the old one. I am going to pull the carb apart tonight, and check all the passages very carefully. Also wondering if I got the float set incorrectly. I'm going to call Holley and make sure I know the correct place to measure the float height, since it is a side hung float. Might also install a power valve block off temporarily just to rule that out as a possible cause, but I don't know if that would send fuel through the boosters. If the PV is blown, my understanding is that the vacuum will pull fuel through the ruptured diaphragm into the vacuum passage.
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