Engine Stalls over speed bumps

[novanutcase]

Hi! For some reason when I go over a speed bump or off of a drive way with a tall lip going to the gutter unevenly the engine almost stalls out. In other words, when one tire hits the bump and goes over and the other hits it right after it almost stalls. Does anyone know why it would do this? When I hit a by speed bump straight it doesn't do it!

 

[phjohnso]

it sounds like you have an electrical issue, like something is shorting out as the car twists over the bump - maybe a ground?

 

[novanutcase]

You don;t think it could be soething to do with the transmission or carburetor?

 

[tbird5866]

I'll agree with Johnson. I can't see how the carburetor or the transmission could cause this problem.

 

[novanutcase]

The reason I said it could be the carburetor or tranny is when I go unevenly over a speed bump maybe the body is flexing which is flexing something in the driveline and binding it. I don't think it would be back at the differential or back of the tranny since they have U-joints on each side of the drive shaft. I'm thinking maybe torque converter. It's kind of like a whipping action when this occurs. If it was a short then it would happen over any bump wouldn't it?

 

[hotrod55bird]

John, did you ever get this problem resolved?
I've had the same situation with my T-bird, I'm running the old Holley t-pot carb's on a 2-4 intake, I think the problem In my situation is the floats bouncing around, goes lean then rich. It happens on speed bumps and dips like yours.
Right now I've got all the parts gathered and going to change cam, intake, carb, throw out bearing and a leaky rack & pinion over the winter.
The cam I've got in it right now is a pretty radical grind from Holman Moody and I'm going back in with an Isky RPM 300, hopefully this will move the power band down in a useable range and I'll be putting an Edelbrock 600 cfm vacuum secondary carb to help get rid of the gas station smell when I park it and improve driveability and hopefully the mileage will improve also.

I saw your bird on another post, that's a beauty.
I started a thread about showing off your t-birds, you should definately put up a couple pictures of yours there.

Richard (hotrod55bird)

 

[novanutcase]

Hi Richard!

I rebuilt the carb but it seems to do the same thing although not as often. I have a feeling it has something to do with the fuel system as it sounds like the motor gets starved. It could very well be that the floats are getting bounced around but I would think that there's enough of a reservoir in the bowl that, at least for that moment, the supply of gas would be enough to keep the motor running.

Also it was mentioned that it may be a short but I notice that if I feather the gas over the speed bump it doesn't stall out so this is what leads me to think it has something to do with the fuel system.

John

 

[A.J.'s Superior Automotive]

I had a problem with my fuel tank pinching the fuel lines against the trunk. My car hasn't been running for years so I don't remember the symptoms.

 

[novanutcase]

I had a problem with my fuel tank pinching the fuel lines against the trunk. My car hasn't been running for years so I don't remember the symptoms.

Hey AJ!

I noticed you have a '64 Nova in your sig. I have a '66 I'm doing a tube chassis build on.

Check this out:

http://www.stevesnovasite.com/forums/showthread.php?t=78088

John

 

[t-bird-art]

check rubber motor and transmission mounts and rub marks inside and outside of all tires.

 

[patd1011]

I know this is an old post but I had the same trouble. It used to stall on RR tracks!!It WAS indeed the floats in the carb. Had the carb rebuilt and problem solved.

 

[t-bird-art]

Thanks for the feedback.

The carb floats have a fine tension spring mounted on the float shaft designed to keep the floats from bouncing around over rough terrain .

When the tension spring is missing, the needle moves off it's seat and fuel immediately spurts into carb flooding the engine.

 

[Ford blue blood]

Thanks for the feedback.

The carb floats have a fine tension spring mounted on the float shaft designed to keep the floats from bouncing around over rough terrain .

When the tension spring is missing, the needle moves off it's seat and fuel immediately spurts into carb flooding the engine.

and starts a fire if the hit was hard enough! Hense the bad rep of the teapots! OOPS, we are talking about a 4100 here not the older teapot. Ya the springs need to be there for more then just bumps.

 

[vincep99]

I don't have that problem on my '63 T-Bird (and I live on a dirt road), but I did have it with an older GM. The problem was the coil shorting out on the firewall. Would not apply to the FE since the coil is in front.

 

[t-bird-art]

Speaking of fire.

Engine compartment fires are no accident or bad luck.

Water/coolant ALWAYS has to flow thru the water jacket under the carburator. Without water flow, the fuel in the carb bowles will boil producing gas vapors that ignite even at normal engine operating temperatures.

Particularily on the 61-63 Birds, original correct heater cores with built in shut off valve are not available. People are replacing heater cores with one that fits and instaling an aftermarket shut off valve in the engine compartment.

Following the 61-63 manual for heater hose routing, the shut off valve will stop coolant flow to the water jacket!

Again, without proper coolant flow under the carb, the carb heats up and fuel boils producing gas vapor that ignite.


You have to use heater hose routing used on 64-66 Birds. This routing provides coolant flow under the carb when the shut off valve is open or closed.

Another case:
Incorrect/inadequate insulation gaskets between engine and water jacet and between water jacket and carb. Again, incorrect gaskets allow carb to heat up and boil the gas. Proper gaskets are critical.

The gas vapors are another reason to never run a overheating engine.

ALWAYS carry a fire extinguisher in the back seat.

 

[boaterbob]

66 has a thin Phenolic spacer under the carb, No water routing