Well, my comment was based on Charlie's comment, after tuning with an O2 sensor. I'm normally looking at a light tan with a carb, but I was always looking for power, not economy. My EFI setup, tuned for power, still runs white. But at light load it's pretty lean, and the fuel shuts off on trailing throttle.

Those Autolites are really well spoken of. But my comment still stands. Put a vacuum gauge on, and make sure the enrichment circuit isn't used at cruise. Whether it's the rods, or a power valve, or whatever, if the gearing-weight-hills put you into the power circuit, the mileage will suffer.

Under the heading of "young and dumb" (as opposed to now, old and dumb), we did a lot of dumb things with power valves, and springs and oil in SU's, thinking we were race car drivers. All we did was buy more gas, and wash down the cylinder walls.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Can the secondaries on that carb be deactivated to run as a two barrel for comparison?
That might atomize the fuel mixture better.
I run a 1.01 Ford flat top on a 292 in an F600, (7500#) ,and get about 10+ mpg, It has a 11/2"  riser block
JOT

As a general rule, four barrel carbs will get better overall fuel economy than will a larger sized two barrel carb.  Part of that has to do with the primary venturies in the four barrel carb being smaller than the venturies in a two barrel carb thus promoting increased atomization of the fuel.  Vacuum secondary carburetors will only be running on its primary side circuits during normal driving operation but the secondary side is still a player in that there is an idle circuit still active there to allow fuel to be constantly refreshed in that end of the carb.  On the Holley and Autolite carbs, that’s to keep the fuel from going stagnant if not using the secondaries very often.  On these carbs, the secondary float level is also important and if too high, can be contributing to increased fuel consumption.  On the flip side of this, the Carter 4V carb has a common fuel level for both the primary and secondary fuel supply but the left and right side of the carbs are independent of each other in regards to float levels.  On the Carter carbs, it’s possible for the outer two cylinders on one bank and the inner two cylinders on the other bank to run at a different air fuel ratio than the other four simply due to the left and right sides of the carburetor simply having different float levels.
 
But beyond all that, there are lots of variables involved to get that fuel mileage up.  While the engine combination and its tuneup is at the top of the list for the fuel mileage, the remainder of the car must also be looked at.  Gearing and tire size are two of the obvious things to consider but in the background is the front end alignment, tire inflation pressures, brake drag, driveshaft angles, and transmission drag.  If running an automatic trans, then this is an area much overlooked as there is a considerable amount of variability within the transmissions both in the clutch packs and the converters.

Lorena, Texas (South of Waco)

I took the Fairlane out for a drive today for the first time in a couple of weeks.  When I first put the transmission in gear to leave the driveway, it felt like the parking brake was engaged: I had to put my foot on the gas to get the car to roll, and it was very sluggish.  I assumed the shoes were sticking to the drums and a little exercise would clear that right up.  Everything felt pretty normal after two stops.  When I reached my destination, I checked how rollable the car was by shifting into neutral with the engine off.  The car immediately started rolling by gravity and I thought I was on flat ground!  Additionally, it wanted to creep at stoplights.  So if the brakes are contributing to bad mileage, it would seem an intermittent problem.

I have thought more about whether the transmission could be the weak link.  Aside from the poor economy, I also feel like there is more engine braking than should be.  I had the converter apart a couple years ago and began to wonder whether I could have installed the stator backwards.  This is the way I assembled it:
 

From what I can tell, that was the way it ought to go.  And I remember checking the one-way clutch and not finding a problem there.  Ted, how would one assess transmission drag?

What about oil?  I use 20w-50.  

Front end alignment is fresh with the front end rebuild.  Tires are 225/70/14s and I tried running them as high as 40 psi; also tried 7.50x14 bias plies at 24 psi with no difference (except much easier steering!  No power steering on my Fairlane).

I'm going to replace the old rear brake shoes this weekend and will see whether there is any perceivable change with that improvement.  

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Unfortunately the FOM has always been a MGP killer. If I recall they take close to 50 hp as compared to other makes that are around 20-25..

I don't believe that for a second

Transmission efficiency is irrelevant if similarly equipped vehicles routinely get better mileage



Lawrenceville, GA

That’s a tough one.  A chassis dyno with the engine simply running at a specific rpm and throttle opening would give an idea of how much horsepower is being required for normal driving.  But that means having a baseline for a normal drag within the transmission and/or driveline in which to compare.  I have run across this in the past on Turbo 350 trannies and the transmissions were simply swapped out for another when the problem cropped up.

Lorena, Texas (South of Waco)

I see.  I have changed the rear brake shoes and adjusted all brakes.  I set the fronts to where the wheel will spin one full revolution before stopping when spun by hand.  The rears are much trickier, I set them to where I could feel a little brake drag but still turn the drum easily by hand.  I erred on the tight side since the shoes are new and will need to wear in.  I will not try to assess economy again until they have time to wear in.

In the mean time, I have been studying my FOM supplement and intend to do control pressure checks and, most importantly, a stall test.  But given the behaviors they describe when troubleshooting converter issues, I suspect I will not find any problems.  And now I'm sure I installed the stator correctly.  Updates as I have them.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Here are some examples of parasitic hp loss with auto's. This one doesn't include FOM but they are right up there with the worst ones.
thought some of you might find this interesting.............

Just in case you're curious, power loss for various auto transmissions:
Please remember these are approximate values, and were provided by Car Craft Magazine.

Powerglide_____18 hp
TH-350________36 hp
TH-400________44 hp
Ford_C-6______55-60 hp
Ford_C-4______28 hp
Ford_FMX______25 hp
Chrysler_A904__25 hp
Chrysler_727___45 hp