First post, bare with me.
I'm pretty mechanically inclined, but I haven't messed around with older trucks much, let alone carburetors.

I just bought a 64 F100, with 292 (Autolight 1100) and 4 speed granny low. The last owner said it was getting 10-12 mpg, and my limited time driving seems to agree.

I've read that around 16mpg is "normal", and the last owner said it was running rich. I don't have a baseline, but it seems to be idling high too.

All in all, the truck runs well, no surging. It seems to live at 45mpg, screams at 50, but I think that's just the gearing. Sometimes get bogged down on Cali hills, but I need to replicate that. I have smelled gas when driving, but when I stop and check, it's not leaking fuel.

My plan for this weekend is to change the plugs, let it idle for 20 minutes, pull the new plugs, and read them. If it is running rich, I think I'll need to adjust either the idle mixture valve, or change jets. I'm not sure which. What jets should be used? How do I set idle mixture?

Anything else I can/should try?

Thanks for your help guys
-L

 

Auto-Lite 1100 is a 1V carb used with 6 cylinder engines. Beginning in 1962, V8's used the Auto-Lite 2100 series 2V carb.

These trucks have the aerodynamics of a brick, city MPG was 10-12, don't expect to get much better. Highway MPG could be 13-16, if you drive no more than 55 MPH

When new, a gallon of regular gas was around 25 cents...and NO one back then gave a hoot about MPG!

 

10 to 12 is about normal, stock. It can be a little better with tuning and a little better with overdrive.

The motor is not screaming at 50mph - that should be in the neighborhood of 2500rpm. If it is loud, it is the exhaust, maybe a louder than stock muffler, or simply a worn out exhaust system.

Get a tachometer to check the rpm so you are not making assumptions. There are tools to do that, if you do not want to have one installed permanently.

If it is idling rich, you adjust the idle mixture. If it is rich while driving and cruising, which is above idle, then you change jets.

No one can tell you which jets should be used. Use what is installed and adjust, if necessary, until it is right.

Since you just got it, a thorough tune up should be done. If the distributor is original, it needs a rebuild, probably the same for the carburetor.

Get a shop manual. They are available as reprints, or on CD. It will have answers to many of the questions you will have and then you don't have to wait 15 minutes, hours, or days for a reply on a forum

 

Thanks for the replies, I plan on taking the advice to heart, esp. the bit about rebuilding the carb.

Can you guys clue me in on how these guys are getting such high numbers? Are their motors not stock?

https://www.ford-trucks.com/forums/1174219-292-mpg.html

 

A lot of reading and study, tuning and dialing in everything to spec. Distributor ignition curve adjustment and carburetor tuning mostly. Learn carburetor function, all the different circuits and how they really work. Distributors and their inner workings. Both widely misunderstood. That's probably why your truck gets 10 mpg. Lots of information on the 2100 carburetor though, and free.

All of the information needed is online, you'll just have to dig for it. What my dad used to call "effective use of source material."

The first thing you want is the Ford Shop manual for 1964. There, you'll find ALL the specifications and such for your truck and engine. Tune-up and troubleshooting. It will tell you to perform a cylinder compression test. This will indicate the general overall health of the pistons and rings and valves. The reason to do this before getting spooled up about anything else, if the engine is clapped out, it needs an overhaul. If it's in good shape, then you can proceed from there.

 

Most people getting on the high end of the teens have overdrive transmissions or real tall rear gearing and that is on the highway, not city. Custom tuning (most important) and even engine assembly can also be at play. So those figures are from non stock trucks and/or engines.

 

I learned a valuable lesson years ago from Hotrod magazine: 90% of your "carb problems" are actually ignition problems misdiagnosed. Properly gapped plugs, good wires, a hot coil and as much advance as the engine will tolerate might make a difference. Or, it could be a carburetor problem...

 

I have been around these trucks for 50 years and wonder the same thing. I haven't had it on a trip but 14 is what I see with my 06 with overdrive.


John

 

The pursuit of higher mpg solely for higher mpg should be treated as the hobby it is. It's mostly for bragging rights, as the money involved achieving those numbers will take years to get back in fuel savings and that is if the vehicle is a driver. If it is more on the show, collector or weekend cruiser side of things, then it is possible that the money will never be saved by the increase.

That said, a lot of people like to make their old vehicles more fun to drive and many of the things you do to increase performance will also increase fuel efficiency. There is a limit, of course, for instance, you don't put a drag race cam in a street engine and get better mileage, but a step or two up from a stock cam, maybe even a little bigger, should give you a nice boost in power and efficiency, when everything is tuned correctly. A compression increase will help both power and efficiency.

Another thing to consider is that many of these old vehicles need transmission work. Many times, the cost to upgrade to overdrive is not that much more expensive.

So you can get it without focusing on it, or as a side effect of another necessary repair but however it happens, don't kid yourself into believing that you are actually going to save money on it. Odds are you won't.

The best game plan is to make sure what you have is working correctly and tuned properly. When I say tuned properly, I don't mean by the book. I mean that you take the time to actually tune it and make it the best it can be.