slant 6 stalling at higher speeds

[deathdust73]

hello fabo, I'm having a problem with my 73 duster. its is a slant 6 and I'm having problems with it stalling (kind of) it wants to do it at two different points 1. after warmed up to normal temp, if i accelerate quickly in park or while driving off, the car wants to die, it has what i call a 'hiccup'. it does it worse if the car is colder, but i got rid of that or most of it once i got a new air cleaner adjusted and tightened the carb it'll do it sometimes in park not so much at take off but will like to get rid of it completely. 2. once warmed up everything is at good temp, she'll drive really good no noises no smoke rattles nothing when driving in the city, but if i jump on the freeway at about 50-60 mph the engine just dies if i let go of the accelerator and give it gas again it'll start back up (ALL while in motion) and it'll keep going off and on so i have to regulate it with my foot, it also does it up hill. it seems only when I'm giving it gas. ill answer any questions to the best of my knowledge and will greatly appreciate the help. thank you in advance

-kevin

 

[73Duster6]

When did you last change your fuel filter? This could be only part of the problem but what you describe some what happened to my 73 /6 and after changing the filter I had no problems so now I always carry a spare filter with me.

 

[TylerW]

That Holley carb likely needs a top to bottom rebuild. I took mine off and run something else, but if you rebuild it get a good kit that has the ethanol-resistant rubber parts.

Those 1920's are notorious for off-idle stumbles and sometimes not so off-idle. Mine would do it randomly, so after it finally started leaking I switched to a 1945 and couldn't be happier.

 

[bigjohnson88]

had the same problem with my car, mine turned out to be the rubber line coming from the gas tank. It was crimped because someone installed the fuel line wrong and it was at a bad angle. I'm not sayin that's what it is, but look for signs of fuel starvation... clogged lines, dirty fuel filter, and I did the fuel line mod to eliminate the hard line from the pump to the carb.

 

[TrailBeast]

Classic lack of fuel volume symptoms. (and maybe an accelerator pump issue also)

Start with filters and work your way all the way back to the in tank screen if you have to.

 

[nm9stheham]

Check and set the carb's float setting; being too low can cause the problem #1.

Have you identified the carb brand/model?

After checking all your lines and filters for fuel delivery as suggested above, and if the problem is not there, then it's time to check the fuel pump. Do this on a cool engine.
1. Remove the coil wire to the distributor to prevent the car from firing, and remove the line form the carb and put into a container and see if it will pump a pint to a quart in 30 seconds while cranking. Be careful, it will want to spurt out and get on everything if you do not control where it goes.
2. Get a pressure fuel gauge and check the fuel pump pressure with the carb's inlet line connected to the gauge. It should pump quickly up to 3.5-5 lbs very quickly when you crank the engine. Then stop and watch the guage; it should hold pressure for many minutes, ideally for hours. If it drops, then the pump has a bad outlet check valve and needs replacement.
3. Remove the fuel pump and make sure the lever is not all wobbly and loose.

Carb kits can be had from Mike's Carburators online, and also has new floats for them; Sorensen still has kits for these too that you can get at Otterzone and perhaps elsewhere.