What would cause my engine to die when hard braking?

[hunt2elk]

I have been messing around setting the adjustable rear brake line proportioning valve on my car. It was a 4 drum factory setup and I converted it to manual disc/drum. Carb is a Quick Fuel 750 mechanical secondary. Ill be moving 10-15 mph and slam on the brakes, and every time the motor dies. It will not fire right back up without playing with the gas pedal a bit. Anybody else ever run into this?

 

[HEMI-ITIS]

Start by checking the fuel levels in the bowls.Then what the timing does when you let off the GO pedal............

 

[hunt2elk]

The fuel in the bowls are both about an 1/8" below the centerline. I am coasting when hitting the brakes, so timing is at 14 degrees with 10 inches of vacuum.

 

[OSDart]

Fuel is probably coming out the rear vent tube falling into the secondary circuit. Try putting a short (1" - 2" ) piece of rubber fuel hose on the vent tube. Or loop both vents together with fuel hose and cut a "V" notch in the top.

 

[moes]

just a thought check your mechanical secondaries to make sure they are closing fully and not hanging open a bit.

 

[69 GTX]

They used to make slosh tubes for the metering plates to cure this.
https://www.jegs.com/i/Holley/510/26-89/10002/-1

 

[hunt2elk]

Fuel is probably coming out the rear vent tube falling into the secondary circuit. Try putting a short (1" - 2" ) piece of rubber fuel hose on the vent tube. Or loop both vents together with fuel hose and cut a "V" notch in the top.

I know the tubes are real close to the bottom of my K&N Extreme air cleaner top now. I actually cut a 1/8" off them already. Any idea how I could try the tubing to see if that would help?

 

[67 coronet]

I know the tubes are real close to the bottom of my K&N Extreme air cleaner top now. I actually cut a 1/8" off them already. Any idea how I could try the tubing to see if that would help?

if you cut em shorter that is more then likely your problem. try looking at a pic of a marine carb to get some ideas.

 

[Dennis H]

I've had this happen, or a least a stumble caught before the stall. Figured it was normal and I had forgotten that this was accepted back in the day. With exception and depending on how hard the application.

 

[Bb70charger500]

Take the cleaner off and try with the hose !

 

[HEMI-ITIS]

Go somewhere where you can pull to the side of the road when it stalls.Before restarting you can check the fuel situation.

 

[oldbee]

They used to make slosh tubes for the metering plates to cure this.
https://www.jegs.com/i/Holley/510/26-89/10002/-1

Probably what you need.

 

[moper]

Reset the float level on the primaries a little higher, and use a vacuum gage to set the mixtures again. I like it just dribbling from the hole, or just visible in the site plug depending. If it's below those levels it can stall.

 

[Joeyt66]

I'd check the float levels, probably go with the slosh tubes. But you're coasting and have only 10 in of vacuum ?

 

[hunt2elk]

I'd check the float levels, probably go with the slosh tubes. But you're coasting and have only 10 in of vacuum ?

Coasting with the clutch pushed in, so the same as at idle. 10" at 850 rpm.

 

[hunt2elk]

I checked the last time I tested the brakes (which I now have finally got set). After it stalled and before restarting, the front bowl was to about 3/4 of the glass and in the rear glass, the gas was just visible. I then restarted the motor and gas was in the center of the sight glasses front and rear. So the gas from the rear bowl is going somewhere. I think I will order a set of these and try them https://www.ebay.com/itm/Quick-Fuel...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649.

 

[hunt2elk]

if you cut em shorter that is more then likely your problem. try looking at a pic of a marine carb to get some ideas.

Is this what you are referring to as a marine application? https://www.ebay.com/itm/Holley-QFT...e=STRK:MEBIDX:IT&_trksid=p2055119.m1438.l2649

 

[HEMI-ITIS]

Coasting with the clutch pushed in, so the same as at idle. 10" at 850 rpm.

With that tidbit of info,I am confident fuel is sloshing into the throat flooding and causing the stall.I'm sure when it restarts that there is at least a puff of black smoke out the exhaust.All that is needed is some rubber hose,can even be clear that you put from vent to vent with a hole or "V" cut in the top middle.Problem solved

NEXT

 

[beanhead]

I checked the last time I tested the brakes (which I now have finally got set). After it stalled and before restarting, the front bowl was to about 3/4 of the glass and in the rear glass, the gas was just visible. I then restarted the motor and gas was in the center of the sight glasses front and rear. So the gas from the rear bowl is going somewhere..

There's the evidence you needed..Gas from the rear bowl sloshes out forwards down the carb while the front bowl fuel is contained. I had the same thing happen once but I left things the way they were because it runs well and it only did it under an extremely hard (almost tire-locking) stop.

 

[hunt2elk]

There's the evidence you needed..Gas from the rear bowl sloshes out forwards down the carb while the front bowl fuel is contained. I had the same thing happen once but I left things the way they were because it runs well and it only did it under an extremely hard (almost tire-locking) stop.

Yeah, thats what I was doing was locking up the tires. I may have to leave it alone also. Tried the tubing trick, but it is physically impossible to get the air cleaner lid on with my drop base.