I posted a couple weeks ago about having some carb issues. Specifically, I'm having trouble with the engine apparently flooding when I brake moderately hard or harder. I have a Holley 4150 double pumper. I just pulled the rear float bowl to double check that I do have a vent baffle (whistle) installed. I do. Any idea how I could still be flooding it out with a whistle installed and a properly set float level? I even lowered the float level some, but the problem persists.

Can fuel somehow wash past the whistle? They don't really seem to seal in any sure way, but I wouldn't think enough fuel could spill by to cause a problem either. It was also suggested that I could run a rubber hose from the front to the rear vent tube and put a hole in the apex. Unfortunately with the clearance I have there really isn't a practical way of doing this, so I'm looking at how to more properly "fix" this problem. I can reproduce the problem while coasting at 20 MPH if I hit the brakes and come to a complete stop very quickly.

I have even double checked the front float level and it is just below where a trickle of fuel spills from the sight plug. I'm nearly certain it is flooding and not starving as I couldn't get it to restart once when I really nailed the brakes, so I pulled the air cleaner and the throttle plates were wet with fuel.

-dath

 

hmmm... that could be a power valve issue.... I had a similar issue and it turned out that 4 parts in my carb were shot, including both power valves

 

Hmmm, good suggestion, though I'm not sure how it could cause this problem? I don't have a power valve on the secondary side, just a plug, you wouldn't normally have two power valves would you??? I have had quite a few backfires up top as I don't have a choke and it takes the right amount of finess to keep the car running after starting it cold and I tend to get impatient

-dath

 

My 80514 1000 cfm carb has 2 power valves... I'm actually thinking in getting rid of both of them (blocking them off) and stepping up with the jetting...
I personally don't really understand too much about carbs.. That's why I bring it to the carb shop if I have problems.. I'm actuall having carb problems right now (hesitation during acceleration).. Tomorrow or on Tuesday, my carb is going to be inspected at the local carb shop and they'll fix it if it needs to be fixed...

 

I had the exact same problem when my fuel pressure was too high. I took my hood and air cleaner off and drove down the street. During moderate breaking fuel would spew out the vent. I turned the pressure down and it has been fine since.

 

Thanks guys. Maybe I should see what my fuel pressure is . . . I haven't checked that, I just assumed it would be fine as I'm currently still running a stock mechanical pump. I plan on putting on a Carter pump soon, but I'm waiting for some parts still . . .

I do have a question, maybe this is telling, maybe not . . . When adjusting the float level, is it normal for fuel to leak out around the adjusting nut? This happens on both primary and secondary sides. I have to very carefully adjust them while keeping things fairly tight or fuel ends up all over . . .

-dath

 

Leaking fuel out the adjusters is normal, its under some pressure. If you have had several back fires and if you are running an older Holley without the blowout protection then the power valve is shot. There is a kit to update older carbs to the new blowout protection.

 

Sounds like your floats are adjusted to high.. Adjust them down and that should correct your problem.. Dave..

 

agree but I do not know why. I adjusted my secondary a little lower than normal and it almost completly eliminated it. Under VERY VERY hard braking it will still stall.