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quick-fuel carb problem on a 460

 
  #1  
Old 02-16-2019, 04:47 PM
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quick-fuel carb problem on a 460

1975 460ci from Lincoln Mark IV
Smog head but thermactor hump removed and exh ports smoothed
Drilled for 7/16 studs and using 1:73 roller tip rockers
Heads decked to flat
Fed Mogal H535P flat top pistons
Comp 252 cam
Comp ration 9:1 calculated
Edelbrock 1726 fuel pump 3/8 line 7-8# fuel pressure
Quick fuel hr-650 4 barrel mechanical secondaries
Edelbrock performer intake



First start, carb flooding…floats set too high… corrected.......Now have fuel dripping from venturies into throat…Can’t seem to get it stopped

Engine runs smooth with quick throttle response, no hesitation



But something is making fuel leak and we can’t find it



Open to any suggestions



john
 
  #2  
Old 02-18-2019, 11:27 PM
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I would remove it, drain it, flip it over. Get a Mitivac hand pump vacuum tester and do a vacuum test on needle and seats.
 
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Old 02-19-2019, 07:36 AM
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Measure fuel pump pressure output. It's rated for 8 psi, but it may be higher than that due to factory tolerances. Then add to that the fact the carburetor is spec'd for only 6.5 psi, so it's at least possible to cause trouble right there.
 
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Old 02-19-2019, 08:48 AM
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thanks Ted.. I've ordered a new (better) fuel pressure gauge. that was my first suspicion. The current gauge is fluctuating between about 6-8 #s and is hard to get an accurate read on it. It's supposed to be here Thursday and I'll start from there. Another suggestion was blocked air bleeds so some carb cleaner thru those might help. Still not ruling out the needle/seat although they look clean and undamaged... more to come !

Thanks Mark... next time it's off, I'll try that
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Old 02-20-2019, 10:07 PM
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Did you try opening gas cap to make sure it venting ? If the tank is building psi then it's got to vent off somewhere. A unvented tank under the right conditions could easily over power the needle and seat.
 
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Old 02-21-2019, 06:12 AM
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thanks Mark, fuel tank is behind rear axle and is vented with vent/rollover valve... but its something I didn't think about.
 

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