97 vs 94. MPG?

[Enbloc]

I've always been a 97 guy but recently I've found myself drawn to the 94's in pursuit of direct a swap that will give me better driveability and mpg.

The 94 should walk all over the antique 97 on paper with its spray bar, vacuum operated enrichment, centre hinged float etc but does it really in the real world?

Any experience or comparisons out there?

[f1builder]

my personal experience with my 52 F1, stock engine, was that the 94 (model 59) did out perform the 97 as to mileage as well as maintenance BUT, the 97 looks way better to old school guys. difference in mileage? can't really pin it down, not enough to make me want to leave the 97 for the 94. just my opinion.

[Ol' Ron]

The only way to test these carbs would be with a A/F meter and tune each carb for best mileage.

[JWL]

The fact that the 94 does a better job of fuel atomizing, at moderate throttle openings, and, therefore, provides slightly better low speed torque numbers indicates a slight improvement in mileage can be expected during normal street driving situations. Having said that, the 97 is difficult to set on the shelf because most people prefer that "look" and it is easier to make adjustments to, and you might need a micrometer-like measurement to see mileage differences depending on your driving style.

[Enbloc]

General concensus seems to be the same as mentioned above.

On a constant speed run the carbs seem to perform the same. I guess once the carbs are running on the main circuits then its a case of a tube and with a hole at the end to meter fuel.
Stop/go around town driving might see an advantage with the 94 but comparison is differcult due to so many variables like driving style and conditions.

[Bruce Lancaster]

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I believe that the 94 will start running on the venturis earlier than the 97, likely the same thing JWL is saying. Venturi/main jet system can meter more accurately than the idle/off idle holes in the base, and the sooner you get into the mains the better for general driving. Not enough air is going through carb to get venturis working properly at extremely low speeds. This is some of the reasoning behind such things as Quadrajets, small primaries so they can meter accurately at lower speed than big ones could. Sort of a catch-22 for rodders, the smaller the carb the better at low speeds, until flow exceeds the proper capacity of the venturis...then you need a big one!
This judgement on the merits is speculative. but as Ron says an A/F meter used to compare from idle to full blast would quickly sort the differences, and those meters are now fairly cheap and available in hotrod catalogs. You could actually see changes in metering and compare the carbs at same RPM's.
Ford descriptions of carb circuit functions in the bulletins cover this with estimated ranges, off-idle hole feeding a declining amount up to 1250 RPM roughly, main circuit feeding and increasing portion of the mix from circa 900 until 1250 when it takes over fully...all estimates of course. The lower main picks up the better.
I believe Ford's design of a new carb to replace the Stromberg was driven by Ford picking up a reputation as a guzzler.

[Enbloc]

Originally Posted by Bruce Lancaster

I believe Ford's design of a new carb to replace the Stromberg was driven by Ford picking up a reputation as a guzzler.

Exactly! But is the 94 an actual improvement over the 97 in regards to mpg?!?

I've been told that official Ford figures showed something like a 4 mpg increase with the 94 over the 97. Not a great improvement.

[40 Deluxe]

A 4 MPG increase would probably have been from about 16 MPG to 20 or so MPG or about 25%. With a 15 gallon tank that's 60 free miles per tank!

Manufacturers today spend 100's of millions to gain a fraction of that and think the've really done something!

[Bruce Lancaster]

4 MPG seems huge to me too!
Ford had mileage standards in the performance testing section of the Service Bulletins, I believe, and used the old Zenith mileage tester to give the dealers a repeatable benchmark when dealing with customers. It was used to run the car through a carefully measured 1/10 of a gallon on a level road...if mileage was bad there, the car had a problem. If it was good, the customer got a lecture on driving habits...
I have here the Performance Services" bulletin from 1938, with charts for acceptable mileage, accel, and top speed fro various models.
Figures are never quite directly comparable, because of the change from 4.11 to 3.78 as the common gear at the same time...but as example:
1935-6 85's, 97's and 48's with 4.11, 22.6 mpg at 20, 15.6 at 60.
1937 85, 3.78's, 26.4 and 17.4...most 37's were 97, only a handful got CG...so this is 97 with higher gears
then on to 1940 same bulletin ...25.5 and 17.4 for 85's with Ford carb and 3.78
Interestingly, the Merc 95 hp equaled Ford at low speed, bettered it at 60! Heavier, bigger engine, but obviously the 3.54 gears worked well.
Lots more interesting numbers in these Performance bulletins.
These numbers were to give the dealer a testable bottom line on economy, speed, and acceleration; if a car could at least match the measured standards it was OK< if not off to the tuneup section.

[Enbloc]

Interesting results.

When its presented like you have, a 25% increase in mileage and 60 miles more to a tank full is considerable from a small 4 mpg increase.

[Butch11443]

I'm running a pair of 94's on a 239 in french flathead w/ the stock truck cam in it. Using 7.5 pv's and #48 main jets. Just came in from a test run. It is just a hair lean at crusing speed,a little rich under full throttle. Also am running a dual-point mallory with 26* in at 2000RPM.I also have an A/F guage permantly in the car along with a vacuum meter.Pull 20in at idle and 14 to 15 in at crusing speed. Will let you know how the milage is after i get a chance to check it. Should be good with a 3:27gear behind it.
Butch

[38 coupe]

4 m.p.g. increase by itself means nothing, you have to know where you start from. A 4 m.p.g. increase from 50 m.p.g. is an 8% increase, not bad but not huge. A 4 m.p.g. increase from 15 m.p.g. is 26.6% increase, that is huge.

I doubt switching to a 94 on my 37 will get me from 15 to 19 m.p.g at 60 miles per hour. I find the 94s to run a bit smoother than the 97s, but the difference is minor enough that on a car I'm trying to keep original, I run whatever is correct.

[chuck stevens]

Has anyone tried one of those early Mercury carbs? I had a 53 monterey that got around 24 mpg. 255 stock with o/d, heavy car. I don't like the looks of them- scary.