Rebuilt engine running rich

Robert Daber

Well-Known Member
Feb 25, 2018
194
12
Point Pleasant, NJ
Rebuilt 351 which has 12 hours on it and today brought it up to 3/4 throttle for about 2-3 minutes. Crossed some wakes and lost RPM's. Poor Engine acceleration and runs extremely rough and very hard to hold idle. My first thoughts where the worst of course thinking that I wiped my Cam being a flat tappet but then while running at 1200 RPM's there is black sooty smoke out of exhaust. You can smell the fuel in the exhaust. So thinking the rebuilt carb might have a float issue. Going to check that tomorrow, the fuel level in the bowls to see the float is working. If I cut off the fuel supply then if it is a float issue the engine should clear up as the fuel in the bowl goes down. My thinking is black smoke would have to be burnt fuel in excess caused by an extremely rich condition.
Just a sanity check to see if I am missing anything else I need to check?
 

deputyrpa

Well-Known Member
Supporting Captain
Aug 28, 2010
1,192
85
Fort Ann, NY
What carb are you running? I'm supposing it's a 4-barrel? Yes, check the choke for proper function. Check secondary for pissing gas into the barrel at idle. That's a sure sign of a float or needle seating issue. I am also assuming the accelerator pumps were rebuilt too? Did you pull a spark plug or two?
 

Robert Daber

Well-Known Member
Feb 25, 2018
194
12
Point Pleasant, NJ
It was the secondary pissing gas into the barrel. Pulled the plugs and completely fouled up. Everyone one was fouled which I would expect to see with fuel going into secondary. The carb had a full rebuild and dropped it back off with the company that did the rebuild. The engine actually started to flooding with fuel at high RPM's because I lost a lot of power and then when I brought it to idle I saw the black smoke in the exhaust and the really rough idle
 

deputyrpa

Well-Known Member
Supporting Captain
Aug 28, 2010
1,192
85
Fort Ann, NY
Yup. Either the float was set too high or the needle would not seat correctly. Must be a Holley, LOL!
 


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