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85 GT stumbles and cuts out at high RPM

2K views 5 replies 3 participants last post by  79PACER 
#1 · (Edited)
85 GT. All stock except for a header back exhaust.

The 4160 carb was just rebuilt with all stock parts. Stock jets and power valve. New coil, plugs, wires, fuel pump, cap, rotor, fuel filter. All grounds look good and tight. Timing set at 11 degrees. Anything above 3500-4000 the car stumbles and pops like crazy. I've done just about everything I can think of. Ideas?

See video.
 
#4 ·
Plugs are gapped to .46. That video was a second gear pull. Timing is now set to the factory 12 degrees.
 
#3 ·
Why was it rebuilt? Were you having these issues before the rebuild? If not then you should open the carb up again and look for debris stuck in a jet or fuel passage. With the RPM it's occurring at there might be something on the secondary side.

Otherwise, take a close look at your ignition system. I'm not familiar with Ford distributors but I've had a GM HEI module give a similar symptom.

Post a better video. That one isn't long enough to be very useful.
 
#5 ·
I decided to rebuild it because the car sat for around 10 years and ran like crap. When I got into it, all the gaskets in the carb were junk. Pulled it apart again and made sure all the passages were free of debris.
 
#6 ·
Update. I bought a Holley Vacuum secondary spring and quick change kit. I did the paperclip trick and noticed the vacuum secondaries were barely opening. I installed a much lighter spring and replaced the vacuum secondary diaphragm and it made the world of a difference. It doesn't bod NEARLY as much as it use to. There's still some hesitation at 5K and I'll try to work that out this week.

I'll try to remember to post a longer video later.
 
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