1956 engine stalls on steep downhills.

Joined
Jun 12, 2021
Thunderbird Year
1956
Just completed a professional carb rebuild, plus a tuneup from expert engine builder. The car now stalls every time it hits a very steep downhill. Professionals are perplexed. Help needed to resolve this gremlins.
 
Joined
Aug 14, 2019
Thunderbird Year
1957
Just completed a professional carb rebuild, plus a tuneup from expert engine builder. The car now stalls every time it hits a very steep downhill. Professionals are perplexed. Help needed to resolve this gremlins.
Does it also do it with hard braking? I think a carb float adjustment is in order or a misplaced fuel pick-up in the tank if it only does it when the tank is low.
 

Pink T-Bird

Active Member
Joined
Aug 11, 2020
Thunderbird Year
1957
Just completed a professional carb rebuild, plus a tuneup from expert engine builder. The car now stalls every time it hits a very steep downhill. Professionals are perplexed. Help needed to resolve this gremlins.
Stalls when changing orientation can be from too little fuel, too much fuel, or loss of spark. you can sometimes tell which by the way it cuts out and more often by how it restarts.
  • if it kinda fades away it is a fuel issue. If it is sharp "off" it would likely be ignition.
  • Too little fuel you'd need to crank a bit, pump the gas, maybe more than once to restart. That would suggest blockage or restriction, or maybe low float.
  • Too much fuel and it would seem flooded and may take extended cranking to restart. That may point to float too high.
  • Spark cutting out could be a frayed or loose wire in the low voltage side of the ignition, moving with gravity as the car points downhill. A bad motor mount could allow the motor to shift and do the same thing by moving or stressing ignition wiring. Car should start right up, like nothing is wrong, once back in normal level ground.
  • There could be other scenarios someone else here may be familiar with.
 
Joined
Jun 12, 2021
Thunderbird Year
1956
Stalls when changing orientation can be from too little fuel, too much fuel, or loss of spark. you can sometimes tell which by the way it cuts out and more often by how it restarts.
  • if it kinda fades away it is a fuel issue. If it is sharp "off" it would likely be ignition.
  • Too little fuel you'd need to crank a bit, pump the gas, maybe more than once to restart. That would suggest blockage or restriction, or maybe low float.
  • Too much fuel and it would seem flooded and may take extended cranking to restart. That may point to float too high.
  • Spark cutting out could be a frayed or loose wire in the low voltage side of the ignition, moving with gravity as the car points downhill. A bad motor mount could allow the motor to shift and do the same thing by moving or stressing ignition wiring. Car should start right up, like nothing is wrong, once back in normal level ground.
  • There could be other scenarios someone else here may be familiar with.
Very enlightening. Will continue to investigate in this direction.
 
Joined
Aug 14, 2019
Thunderbird Year
1957
I think he stated that everything has been refurbished and gone over. There was another fellow who just had his carb rebuilt to factory specs and the choke was not working correctly. Just a choke cover adjustment was all it needed. Every car and carb has it's own personality. Just because it's set to specs doesn't mean the carb likes it. Different float seats where a micro millimeter in hight can make a difference. I'll stick with checking the carb float adjustment. The situational malfunction still points to it.
I had an intermittent ignition issue where it would just die unexpectantly. Replaced the whole ignition system from plugs, wires, points & condenser, coil and it turned out it was the coil resistor with a broken ceramic insulator causing an intermittent connection.
 
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