1957 8 MPG

Joined
Aug 14, 2019
Thunderbird Year
1957
Yeah 8 MPG is pretty bad....something seems amiss; perhaps a leak ? Even some of the big block muscle cars of the 60s
were better than that.

HOWEVER, if the car is a pleasure cruiser or a "once a month" driven garage queen and runs alright otherwise then perhaps monkeying with things may do more harm than good.
I sometimes wonder if it was rebuilt with a bit of modifications I didn't know about. I just assumed it was as close to original but I had no idea. Young & dumb, but it ran and have no reference as to if it was enhanced or not. Quite possible, That was the thing to do at the time. ' better than original' so the shop could brag. But dang, It goes like a bat out of hell. Subtle great power.
 
Joined
Feb 9, 2019
Thunderbird Year
2002
If you're not getting black smoke out the exhaust after it warms up and the plugs aren't fouling AND you don't smell fuel on the dipstick and the oil level isn't gradually rising I'd leave it alone. Be aware though that if mechanical fuel pumps
rubber parts start to fail it can put fuel in the crankcase, affect mileage and wash down engine cylinders (not good) - so that is what those last two checks determine. If you really want to delve into that issue here is a video that's enlightening, you can skip to about 6:30 minutes into the video to see how oil dilution can occur:


Also if somebody modified the rear grea ratio, mileage will be affected; simple to check and there are several Youtube videos that show how to determine that ratio by turning a rear wheel and counting driveshart revolutions. And yes, "Hot Rod Harry" types would increase carb jet sizes and play other games to try to get a performance boost at the expense of mileage when gas was eighteen cents a gallon; I see it a LOT on vintage Corvette carbs.
 
Last edited:
Joined
Feb 29, 2020
Thunderbird Year
1957
Just checked my milage, just a hair over 8MPG. All stock and non-ethanal fuel, only local driving. No rich smelling exhaust. last I checked 20yrs ago it was about 7MPG.
Wow, that’s terrible! I’ve had my 57 for 10 years now. It has a plaque on the glove box where, in 1958, it took 1st place in an economy run getting 27 mpg! I’m sure they were coasting and did everything they could to get that efficiency. He also installed a switch on the dash going to the kick out solenoid to change from regular driving to overdrive. To get that low in GPM, it’s a combo of a lot of things from valve compression to carburetor to ignition performance. I’d start out observing gas entering carb throat to see if it is even. Check vacuum idling. Should be around 19 steady. If not steady, problems with valves. Get as high a vacuum by adjusting the two carb needles, then lean back off the vacuum to 18 or 17. This should be checked after you plug off vacuum to the distributor. While plugged, check timing. Add one degree for every 1000’ above sea level. Their are 3 adjustments to do for vacuum advance. This procedure is described in the shop manual. GOOD LUCK!
 
Joined
Feb 29, 2020
Thunderbird Year
1957
If you're not getting black smoke out the exhaust after it warms up and the plugs aren't fouling AND you don't smell fuel on the dipstick and the oil level isn't gradually rising I'd leave it alone. Be aware though that if mechanical fuel pumps
rubber parts start to fail it can put fuel in the crankcase, affect mileage and wash down engine cylinders (not good) - so that is what those last two checks determine. If you really want to delve into that issue here is a video that's enlightening, you can skip to about 6:30 minutes into the video to see how oil dilution can occur:


Also if somebody modified the rear grea ratio, mileage will be affected; simple to check and there are several Youtube videos that show how to determine that ratio by turning a rear wheel and counting driveshart revolutions. And yes, "Hot Rod Harry" types would increase carb jet sizes and play other games to try to get a performance boost at the expense of mileage when gas was eighteen cents a gallon; I see it a LOT on vintage Corvette carbs.
I had gas in my oil a few years ago and traced it down to a hole in the fuel pump diaphragm. Vacuum from the intake sucked gas from the pump OR gas bled through into the pump mounting base. Definite smell of gas in oil. One thing positive it did was to clean up the valves that had built up of the parifin from the older type of oils that were used back then!
 
Joined
Aug 14, 2019
Thunderbird Year
1957
If you're not getting black smoke out the exhaust after it warms up and the plugs aren't fouling AND you don't smell fuel on the dipstick and the oil level isn't gradually rising I'd leave it alone. Be aware though that if mechanical fuel pumps
rubber parts start to fail it can put fuel in the crankcase, affect mileage and wash down engine cylinders (not good) - so that is what those last two checks determine. If you really want to delve into that issue here is a video that's enlightening, you can skip to about 6:30 minutes into the video to see how oil dilution can occur:


Also if somebody modified the rear grea ratio, mileage will be affected; simple to check and there are several Youtube videos that show how to determine that ratio by turning a rear wheel and counting driveshart revolutions. And yes, "Hot Rod Harry" types would increase carb jet sizes and play other games to try to get a performance boost at the expense of mileage when gas was eighteen cents a gallon; I see it a LOT on vintage Corvette carbs.
Carburetor was rebuilt last year after the accelerator pump diagram started leaking. Had same milage before rebuild. Original AC fuel pump rebuilt as it started leaking through the weep port also. Ethanol finally took it's toll after 30 years. Gears have not been changed. I've had the same milage since the engine was installed 40yrs ago.
I'm just going to assume there may be a more radical cam and maybe slightly more cubic inch displacement when rebuilt. It runs perfectly other than being thirsty. No soot nor unburned or rich fuel smells from the exhaust.
 
Joined
Feb 9, 2019
Thunderbird Year
2002
Sounds like plenty of "due diligence" performed; as I mentioned before prob just "embrace the suck" as Navy SEALs say and drive and enjoy the car. Its just unfortunate with $5/gallon gas now that its become a bigger issue.
 
Joined
Feb 19, 2020
Thunderbird Year
1955
Just checked my milage, just a hair over 8MPG. All stock and non-ethanal fuel, only local driving. No rich smelling exhaust. last I checked 20yrs ago it was about 7MPG.
First check your timing with the vacuum advance disconnected. Then check to make sure your vacuum advance is working. If that's all good, rebuild or replace your carb. 7mpg is stupid low.
 
Joined
Aug 14, 2019
Thunderbird Year
1957
Just did a full tune up: plugs, wires, points, condenser, coil, coil resistor, rebuilt carb & fuel pump. Checked timing and advance all working to spec.. Gas is fresh. The MPG has been consistent since the engine was installed 40+ years ago. I have no idea what cam was installed by the very reputable Ford rebuilder but it runs great. The plugs I pulled were Proper color and not fouled at all.
 
Joined
Aug 14, 2019
Thunderbird Year
1957
@Ward 57 ,. Pssstt, hey Ward, do you occasionally suffer from "leadfoot itis", I know I do. Kills my fuel economy.....
Usually its pretty tame driving around town, Haven't had it on the highway in ages to check highway MPG as life got in the way and it languished for about 20 years and have spent the last two resurrecting it as one system failed after another from sitting and just moving around. Have it all sorted now.
I must admit at times I stomp on it and listen to the rumble out the back and the howl of the carb sucking air & fuel while knowing since I had the brake booster rebuilt I can haul it down quickly and safely.
 

ron56

Active Member
Joined
Mar 17, 2020
Thunderbird Year
1956
Mileage report:
I just did a 162 mile round trip (mileage checked both by Goggle maps and my GPS). I filled up with ethanol free gas and then on the return trip stopped at the same pump at the same spot and packing the tank, the car took 9.8 gals. On the trip I was on the freeway for about 20 miles at 70 mph and the rest of the trip was on a state road going 60 to 65 mph. My car is a 1956 with auto and the 312. I have changed the rear end to a 3.07 ratio, added a Holley 1848-1 carb (465 cfm) because I live at 4,600 ft I went down 3 jet sizes (now #56). I made my distributor from a truck unit to get the tach drive and added a vacuum advance can. The original truck distributor didn't have any provision for vacuum advance. I don't use the factory timing settings. I have a base timing of 20 deg. and all in with the mechanical advance is 36 deg total at 3,000 rpm. There is a range of 18 deg from the added on vacuum can. I use full manifold vacuum not ported at idle.
IMG_0774.JPG
 

ron56

Active Member
Joined
Mar 17, 2020
Thunderbird Year
1956
That would be correct if your talking about emission controlled engines, no question. The OEM's would go for retarded idle timing to help burn off the hydrocarbons. Later burn equals higher EGT. You can run a experiment by leaving the ported vacuum in place and with the standard base timing loosen the distributor and add more timing and you should find the idle speed will increase to where you need to back the idle set screw off a bit.
 
Joined
Aug 14, 2019
Thunderbird Year
1957
Mileage report:
I just did a 162 mile round trip (mileage checked both by Goggle maps and my GPS). I filled up with ethanol free gas and then on the return trip stopped at the same pump at the same spot and packing the tank, the car took 9.8 gals. On the trip I was on the freeway for about 20 miles at 70 mph and the rest of the trip was on a state road going 60 to 65 mph. My car is a 1956 with auto and the 312. I have changed the rear end to a 3.07 ratio, added a Holley 1848-1 carb (465 cfm) because I live at 4,600 ft I went down 3 jet sizes (now #56). I made my distributor from a truck unit to get the tach drive and added a vacuum advance can. The original truck distributor didn't have any provision for vacuum advance. I don't use the factory timing settings. I have a base timing of 20 deg. and all in with the mechanical advance is 36 deg total at 3,000 rpm. There is a range of 18 deg from the added on vacuum can. I use full manifold vacuum not ported at idle.
View attachment 22914

Mileage report:
I just did a 162 mile round trip (mileage checked both by Goggle maps and my GPS). I filled up with ethanol free gas and then on the return trip stopped at the same pump at the same spot and packing the tank, the car took 9.8 gals. On the trip I was on the freeway for about 20 miles at 70 mph and the rest of the trip was on a state road going 60 to 65 mph. My car is a 1956 with auto and the 312. I have changed the rear end to a 3.07 ratio, added a Holley 1848-1 carb (465 cfm) because I live at 4,600 ft I went down 3 jet sizes (now #56). I made my distributor from a truck unit to get the tach drive and added a vacuum advance can. The original truck distributor didn't have any provision for vacuum advance. I don't use the factory timing settings. I have a base timing of 20 deg. and all in with the mechanical advance is 36 deg total at 3,000 rpm. There is a range of 18 deg from the added on vacuum can. I use full manifold vacuum not ported at idle.
View attachment 22914
Very resourceful to find a truck dist. with a tach drive. Had a previous owner tossed the original dist.? They are now worth thousands of $. I admire your work.
 
Joined
Feb 9, 2019
Thunderbird Year
2002
That would be correct if your talking about emission controlled engines, no question. The OEM's would go for retarded idle timing to help burn off the hydrocarbons. Later burn equals higher EGT. You can run a experiment by leaving the ported vacuum in place and with the standard base timing loosen the distributor and add more timing and you should find the idle speed will increase to where you need to back the idle set screw off a bit.
Correct, you want to run FULL manifold vacuum on these early pre-emission engines; you'll get a smoother idle, it'll be cooler running among other benefits...
 

ron56

Active Member
Joined
Mar 17, 2020
Thunderbird Year
1956
Ward57:
When I bought the car it came with a late style manifold and what looked like a passenger distributor. (bought the car at auction not running, have no idea about it's history) I really wanted the tach to work not to use, but I didn't like the idea of a gauge just sitting there. Turns out that after installing the smaller steering wheel I use the tach because I can't read the speedometer in the 60 to 80 mph range. I knew I needed a 1957 distributor to go with the late style carburetor I added, if I was going to have a tach drive. Problem was when I looked 4 years ago the cheapest 57 distributor was 1,500. Poking around on Ebay I found the truck distributor for $30. It had no vacuum advance and was equipped with a governor. It also had a reverse cut distributor gear, so I guess the truck had a cam gear drive and not a chain. I cut up the car distributor to get the mounting bracket for the vacuum can and I used the gear, and all the bits for the mechanical advance. I had to do a fair amount of machining to get everything to fit and to index the rotor properly. I added a lower bushing so it's a pretty rugged unit.
 
Joined
Jan 1, 2021
Thunderbird Year
1955
Here is a quote from Ted Eaton (eatonbalancing.com), Engine Master's Competition Y-block engine builder: "I use ported vacuum. It adds another level of complexity to control the idle and low rpm ignition timing using manifold vacuum on non-emissions engines such as those made in the Fifties and early/mid Sixties. Surging at low speed cruising tends to be an issue with using manifold vacuum for the distributor on my end."
 
Joined
Feb 9, 2019
Thunderbird Year
2002
Maybe its Fords, my Chevelless and Corvettes use full manifold vacuum whether solid or hydraulic lifters, dual quads or single carb and I've never had a tuning problem with them. Surging (or idle "hunting") is often caused because a tuner has "chased" a good idle until too much of the carb's internal transfer slot is exposed and they subsequently play with timint go try to fix it.
 
Top