Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
What would make Holley Carb overflow when hot?
#1
Its a Mercury racing HP500 carb,(Holley 830 double pumper marine version ) we have already rebuilt it, set the float levels multiple times and it keeps doing same thing,
once you have been out running for a while and idle down to dock it will sputter and be way rich, as you look down carb bores you can actually see fuel trickling out of tubes. Makes it a scary propisition to dock.
When its cold it does not do this, idles perfect , nice 13.9-14.1 AFR , no fuel dripping.
Driving me bonkers..
Its sitting on a Ebrock Victor Jr with no heat passges so intake stays relatively cool.
2008 Saab 9-7x Aero 6.0V8 AWD 5000lbs
[email protected]
resonator delete,homemade cold air,otherwise stock
1994 Mustang Gt convertible.. stock

[Image: image.php?u=20525&type=sigpic&dateline=1385997332]
Reply
#2
things off the top of my head:

-Fuel Pressure too high (no more than 8psi during the whole trip)
-Bowl vents plugged
-Viton coated needle and seat not sealing properly
ASE Master Tech with 15 years experience


Daily Driver: 1994 GMC Sonoma, Extended Cab, 2WD, with the 4.3 V6 Vortec.
Future plans/projects: Finishing that darn 64 Malibu SS
Reply
#3
this happened all the time with my Holley 750 DP that was on my Firebird...

ended up being plugged bowl vents.
2004 Pontiac GTO M6 Barbados Blue/Black Leather (one of 271)

Skip-shift eliminator, 160 T-stat, K&N FIPK, Resonator delete, 255/45 out back, 245/45 up front, 5% tint, 28mpg hwy!

[Image: 7252301066_b19f58654b_z.jpg]

2008 Dodge Charger SE Plus 3.5LSOLD

2007 Toyota Yaris SSOLD

1997 Lincoln Mark VIII<Sold

1970 Olds Cutlass S 350/350 B&M reverse valve body (Sold)

1969 Pontiac Firebird 350/400 NOS (Sold)
Reply
#4
The tubes as in the vent tubes (one on each side, 2 total) right? The only way fuel could be getting up through thoes is if your fuel pressure is too high, your needle/seats aren't sealing properly, or the fuel is boiling in the bowls. I have seen a lot of floats that are bent wrong, which makes it near impossible to get the needle to close all the way (unless you turn the needle so far down the adjuster nut up top has nothing to grab on). I would pop the bowl off and see how far the float has to lift up before the needle would cut the flow.

Also, I would imagine since its a marine carb, it would have some sort of foam in the bowl to keep the fuel from sloshing around? If so that could be interfering with the float....
Space for rent
Reply
#5
No , not the vent tubes, it leaks out the venturi where fuel normally comes out when it is running.
Stock fuel pump.
Only does it after it warms up.
2008 Saab 9-7x Aero 6.0V8 AWD 5000lbs
[email protected]
resonator delete,homemade cold air,otherwise stock
1994 Mustang Gt convertible.. stock

[Image: image.php?u=20525&type=sigpic&dateline=1385997332]
Reply
#6
The only way that can happen is if the pressure inside the bowl goes up and there is no place for the fuel to go. Obviously the main jets are designed to allow the vacuum of the engine pull fuel through them, not have fuel pushed through them. I would check the vent tubes as suggested.
Space for rent
Reply
#7
okydoky!
2008 Saab 9-7x Aero 6.0V8 AWD 5000lbs
[email protected]
resonator delete,homemade cold air,otherwise stock
1994 Mustang Gt convertible.. stock

[Image: image.php?u=20525&type=sigpic&dateline=1385997332]
Reply
#8
maybe power valve issue????
Reply
#9
The power valve lets fuel through below the plate. If he is seeing fuel coming out of the booster venturi http://racingarticles.com/images/64/stra...er-500.jpg then the only culprit would be to high of fuel pressure in the bowl (either too much fuel pressure after the regulator, or there is some sort of plug in the venting system which would increase the pressure inside the bowl.) At idle the throttle plates are closed, which means there is no air flowing past the boosters, which means there is no fuel being pulled out of the boosters. The engine is running off of the idle circuit (contolled by the needles on the 4 corners) at idle, the main jets are not used at all.
Space for rent
Reply
#10
There could be some flakes of rust or other shit stuck in the needle and seats, had that happen and caused what you describe.
Played and DUMPED by The Woman Who MATTERS.
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)