Hard right turn - engine stumbles and dies

[Terry Stapley]

Thanks for all of the suggestions guys, I am taking notes!!

Ron: The fuel pump is on the drivers side right by the tank fuel outlet and I will check to see if there is any debris in it again because I cleaned it out last year when this problem developed. This was my first time have it "detuned and then tuned" for emissions!

Zach: The carb floats are brass and they are empty!!

Thanks again for all the help!!

[Anthony]

It sounds kind of like you're getting too much fuel in the bowel like you eluded to earlier. Maybe a float is sticking/binding, needle/seat is sticking open/binding , allowing more fuel than needed in the bowel? Which floods out the engine?

Interesting problem.

[Michael P. Wole]

Too much fuel in the bowel ...so that is the cause of my flatuation problem!

[Terry Stapley]

Update!!
I adjusted the carb floats up until I just had fuel exiting the sight holes, buttoned everything up, and took her out for a test drive. Now I remember another reason why I had adjusted the floats down a bit as it wants to stumble when accelerating mildly from a stop!! It also still has the hesitation in the right turn!! I am going to adjust to floats down a tad and see if that gets rid of the stoplight stumble!! It worked before!!
Still no idea on the right turn hesitation though and it isd frustrating to say the least!!

[392cobra]

The stumble is from a lean condition ,not a rich condition.
You need a bigger shot of fuel at that point.Could be a change in nozzles or a different pump cam.

[Terry Stapley]

Thanks Fred, but if I adjust the floats down just a bit the stumble goes away!! And it does not take much of a down adjustment!!
I am confused!!

[392cobra]

Originally Posted by Terry Stapley

I am confused!!

I found I got used to it after some time.

[392cobra]

Terry,
Any chance you can put another carb on there to be sure your right hand turn problems are indeed to carb ???

[Pete Munroe]

Guys,

VERY SIMILAR PROBLEMS. Wll try to relate the problems.

I have a 750 Holley dbl pumper, "4779-9", on a 347 with 10.6 comp, 224/228 cam roller. rear gear is 3:54. ERA 289 car.

The carb DOES have vent whistles, no jet extensions...about 4 years old, 11,000 miles. The fuel pressure was at 8 psi...is now down to 4.5 since I got a gauge and adjusted it down. Uses an electric pump.

Floats have been up, down, and where they are supposed to be...fuel level at the edge of the site hole, maybe a little dribble if the car shakes. Performance is always the same.

OK...car in motion...

1. Slam on the brakes, the engine almost stalls as you come to a stop. I think it is going rich?...fuel sloshing in from rear float bowl?

2. Hard right turn...(turn two at Willow Springs)...steady state speed...third gear, about 3000+/- RPM engine breaks up like a popcorn maker...NAIL it as you exit the turn it pulls hard all the way to turn three right up to 6500....no problem. Front straight at Willow, about 1/2 mile, pulls like a freight train. No miss.

OK...is this problem a function of partial throttle weak vacuum signal and too large a carb for the application?

I am wondering if at ~3000 RPM I am in the range where, under load, the carb vacuum signal is causing the POWER VALVE to oscillate...rich, lean, rich, lean.

TEST to come...hope to soon having access to a 600 cfm dbl pmpr and see if the mid range response is correct.

If you read the HOLLEY formula for carb size, an engine at 350 inches and 6000 +/- rpm only needs 600 CFM...

OK, you may make more power with a 750...but drag racing normally involves a minimum of lateral G-force.

As to the Double Pumper tendency to STALL as you slam on the brakes, I have 2 other fellas with the same problem...center hung floats?...one is sloshing UP, the other is swinging down.

My side hung 1850 Holley, 580 CFM on my 67' 300hp/327" Corvette has NONE of the problems the CENTER HUNG carb on the Cobra has...the Vette is on 8 inch wide wheels so it corners fairly hard steady state.

Know that the center-hung carb is supposed to respond equally under left/right loads, but it seems inherently challenged by acceleration/decelleration...LOOKS COOL...but other than that...?

Pete

[Rick Parker]

Roscoe:
It looks as if you cut those with a saw, did you seal them? That looks to be a modified stock float. The OEM skin prevents fuel from being absorbed. With the inner core exposed they will absorb fuel, become heavy and unresponsive to fuel levels.