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For the past month or so I have been experiencing drivability issues on my '55 Firedome. The symptoms can best be described as hesitation during acceleration, not from a dead stop but usually above 30 mph. I had a local old car shop check it out; they experienced the same thing after a couple test drives. They tested my fuel (I've been using ethanol free gas), checked and cleaned the input screen in the fuel tank, cleaned and gapped the plugs and removed the mixture screws in the carburetor and blew out with compressed air. They thought these actions cured the problem but on the way home from the shop the car showed the same symptoms.
The carburetor has been rebuilt within the past 3 - 4 years and the distributor was rebuilt by Tim Bowers within the past year. Plugs and wires are less than a year old.
Everyone - including me - thinks it is a fuel problem, but maybe we are overlooking a problem elsewhere. Any ideas from the experts?
Mark
Hi Mark,
I am far from an expert, but I have had a similar issue, not on my '55 but on the '51 I have been working on.
It turned out to be my fuel pump. I had the pump rebuilt when I first started working on the car, so it didn't occur to me that it could be the problem. Well it was.
Like you, I checked everything else I could think of before changing the pump.
Before I changed it, the car would idle all day long, and if I drove at slow speeds it was good. It was when I tried to put a load on it by picking up speed, or especially going up a hill that it would start to break down. The rebuilt pump could not keep up I guess. I have had no problems since I changed it.
Actually, I should have asked, are you still running a mechanical pump?
Dean,
Thanks for the suggestion. Yes, still the mechanical pump. It is a NORS rebuilt pump but with today's gas and sitting for who knows how long before I put in on the car probably worth a shot to try a fresh rebuilt pump, which I think I have in my parts stash. I'll update if that solves the problem. Again, thanks for your time and suggestion.
Mark
How exactly did your car mechanic clean out the screen in the tank ? I was under the impression that the tank had to be physically opened up to get to the screen.
There could be crap in the fuel line that is creating a blockage.
Pressure test your fuel pump. It should be maximum 5 - 7 lbs. Nothing more than that.
But my money is on your accelerator pump. The rubber or leather surround tends to dry up, so that the volume of fuel that your engine needs for rapid acceleration is not being delivered. It's an easy fix once you remove the air horn of your carb.
The definition of a 'carb being rebuilt' varies widely. In addition to replacing the gaskets, etc., the carb needs to be dialed in to the specs in the shop manual. Who rebuilt the carb and did they use a modern kit ?
Based on the description of the work your old car mechanic did, I would not use him again.
Ron
Dean...thanks for your suggestion. My more mechanically talented car club buddy and I changed the fuel pump Friday evening and it tested fine. Drove the car on a couple long shakedown runs Saturday and Sunday - Saturday a car show 50+ miles away and Sunday a club driving tour - and the car did not skip a beat. Your advice was much appreciated!
Ron...the carb was rebuilt several years ago by a carb shop in Kansas that Tim uses and recommends. I think it is named The Carb Shop. As for not using the guys that did not suspect the fuel pump, that thought has crossed my mind 
Mark
Mark, sometimes you get lucky, glad the problem is solved.
I also went on a small club tour on Sunday, only about 8 cars (two Desotos).
Could be one of the last of the season for our club.
