Stalling and stumbling questions

[Larry T.]

I have had two issues that I am wondering whether or not are normal.

1) When I go over a speed bump, slowly of course, only allowing my passengers side to hit the bump I get a stumble. I think if I hit the bump a little faster it may stall. For some reason hitting it centered does not react the same. As for the drivers side, I do not know.

2) Recently when someone pulled out in front of me and I had to stop abruptly my engine stalled. I had been travelling at about 20-25 mph. It took about 5-6 seconds of cranking to start back up.

I have an original 3247 carb that was restored by Eric Jackson about 9-10 months ago. I have had no problems with it. I think the floats are properly set. When I take off the check plug/screws the gas does not come out until I lightly rock the car.

One more thing. Is it normal for fuel to come out the top of the bowl at the adjusting nut when adjusting the floats? If not, what is that symptomatic of?

[Timothy B.]

Re: Stalling and stumbling questions

Larry,

I think it's normal for fuel to come out the top when you loosen the lock nut to adjust the float level.

On the stumbling, try adjusting the A/F emulsion screws after the engine warms good and set the idle at approx 650-700 if it's 300hp engine.

[Larry T.]

Re: Stalling and stumbling questions

Thanks for the info, in this case it is a 425/427. The idle is at about 800.

[Gene M.]

Re: Stalling and stumbling questions

Quote: One more thing. Is it normal for fuel to come out the top of the bowl at the adjusting nut when adjusting the floats? If not, what is that symptomatic of?

No, It sounds as if the float is too high. Adjustment screw is way above the necessary fuel level. Maybe a bad seat on the inlet. The sight plug hole bottom edge should be the fuel level running.

Don't drive car like that can cause fire..........

[Clem Z.]

Re: Stalling and stumbling questions

Quote: One more thing. Is it normal for fuel to come out the top of the bowl at the adjusting nut when adjusting the floats? If not, what is that symptomatic of?

No, It sounds as if the float is too high. Adjustment screw is way above the necessary fuel level. Maybe a bad seat on the inlet. The sight plug hole bottom edge should be the fuel level running.

Don't drive car like that can cause fire..........

that is incorrect as there is fuel pressure there when you loosen the locking screw to adjust the float level and it will squirt out when you loosen the screw. when the carb was rebuilt was the "spash baffle" put back into the bowl vent?

[Larry T.]

Re: Stalling and stumbling questions

...The sight plug hole bottom edge should be the fuel level running.

I guess that is what strikes me as being odd. The fuel level is at the bottom of the sight plug hole, but it still seeps fuel at the top of the bowl upon backing off the set screw.

[Larry T.]

Re: Stalling and stumbling questions

that is incorrect as there is fuel pressure there when you loosen the locking screw to adjust the float level and it will squirt out when you loosen the screw. when the carb was rebuilt was the "spash baffle" put back into the bowl vent?

I do not know, I will have to check with Eric or pull the bowl off to look. Thanks.

[Clem Z.]

Re: Stalling and stumbling questions

I do not know, I will have to check with Eric or pull the bowl off to look. Thanks.

the original type is no longer available from holley but this type will work

[Clem Z.]

Re: Stalling and stumbling questions

i would also recommend using .097 diameter needle and seat vs the .110 diameter one for street driving because the smaller orifice will control the fuel level better. if you do auto crossing or do track days use the .110

[John H.]

Re: Stalling and stumbling questions

I guess that is what strikes me as being odd. The fuel level is at the bottom of the sight plug hole, but it still seeps fuel at the top of the bowl upon backing off the set screw.

Larry -

That's because there's fuel pressure all the time at the bowl inlet/needle and seat, regardless of the fuel level in the bowl itself; the fuel in the bowl isn't under pressure.

[Larry T.]

Re: Stalling and stumbling questions

How about the stumble when going over the speedbump or the stalling when coming to a sudden stop? Normal?

[Joe C.]

Re: Stalling and stumbling questions

How about the stumble when going over the speedbump or the stalling when coming to a sudden stop? Normal?

Stumble when going over a bump is more likely an ignition problem. A loose connection or partial break somewhere will cause the ignition to "cut-out" when the engine is jarred. Check for bad/loose wires. First place I would look is at the distributor breaker plate ground wire.

Stalling when coming to a hard or sudden stop is characteristic of the Holley carb. It is due to fuel slosh in the float bowl(s). I have not yet figured out how to cure it completely. You might want to try raising the primary float level, and/or installing extensions on the primary bowl jets.

[Clem Z.]

Re: Stalling and stumbling questions

Stumble when going over a bump is more likely an ignition problem. A loose connection or partial break somewhere will cause the ignition to "cut-out" when the engine is jarred. Check for bad/loose wires. First place I would look is at the distributor breaker plate ground wire.

Stalling when coming to a hard or sudden stop is characteristic of the Holley carb. It is due to fuel slosh in the float bowl(s). I have not yet figured out how to cure it completely. You might want to try raising the primary float level, and/or installing extensions on the primary bowl jets.

for sudden stop stalling you need a baffle in the rear float bowl as gas can come out of the secondary bowl vent into the carb flooding it. GM put a baffle in the primary side float bowl to prevent fuel from coming out of the primary bowl vent when accelerating.