I have a 298 out of a 68 carb with points. I get 12 mpg at 75 mph. I am wondering if $2000 for a fuel Inj. Is worth it? If it gives me 5 mpg it might be worth it. Anyone have any first hand experience with it? I have read great reviews and bad reviews but first hand is always more reliable. Thanks

 

Is this the Holley throttle body or the sequential system? Either way, I can't see that it would give you 5 more mpg at 75. Wind resistance is the bigger factor with these trucks, which have the aerodynamics of a barn. What gears and carb are you running?

 

Stock rearend 3.91 or 3.92. Holley carb. With an aod out of at 1981 f-100.

 

Check into having the engine dyno tuned, Holleys (the older ones) are notorious for blowing power valves which will kill mileage. What Holley carb is it, there are several syles and sizes? I like Holleys, own several, built a heck of alot more of them but have found better mileage in the Carter/Weber/Edelbrock AFB carbs. You can get them cheap at swap meets and craigslist. Kits are about $25 at Summit Racing. Great performance and you should be getting 15-17 mpg with one. Alot cheaper than fuel injection.

 

I would Do what Dave said , but I would also upgrade the ignition system. Without knowing the details of your engine , no one can give you an answer as to what will give you the most bang for your buck mileage wise . I mean the advice for a high mileage 289 , all stock with a 750 double pumper on it is going to be wayyy different than a rebuilt 289 with a good cam and heads and a new 600 .

Make sure what you have right now is in its peak shape with what you have . When was the last time you had a tune up ? Who set up your carburetor , when was the last time it was rebuilt ? What is the timing set at ?

If all of that has been taken care of , then 12mpg isnt very great . What carburetor are you running exactly ? Electric fan ?

There are ALOT of ways to increase mileage on a vehicle .

 

Jeff,

I see you are from Illinois. What part of the state? The reason I am asking is that I have a wide band air/fuel ratio gauge from Innovative Motorsports that I could help tune your carb. I live in east central Illinois (Charleston).

 

As far as I know the motor is a stock one out of a 68 mustang. Miles unknown. The carb is a Holley 4150 with electric chock. We set it up so it is where it should be. Rebuilt I don't know. Electric fan. It is still running on a point dist. I live in Peoria.

 

Jeff,

In my opinion, 600 cfm is too large of a carb for a 289. I would suggest running a 500 cfm carb on your engine.

Also, you should be getting in the mid to upper teens with your miles per gallon even with a points distributor.

 

You need to get the "list" number on the air horn, that will tell me a lot about what carb you have. There are several 4150 style Holley carbs. Do you know the CFM, the jet size, accelerator nozzle size, power valve number, etc... There are a ton of variables with Holley carbs. Need more info to help you better.

 

For fuel injection to be really efficient you will need a lot more inputs than what you currently have on you '68 engine. And a goal of 5 mpg at 75 mph will require a lot more than efficient fuel flow. Changing your rear axle would have the biggest impact but you will still have to overcome the previously mentioned "barn door" effect.

Holley has a carb selector on their website (http://www.holley.com/applications/CarburetorSelector/CarbSelection.asp). Just remember to be honest as possible about your intended uses or you will be disappointed. They say that the number one error that most people make is to over-carburate their engines. Smaller carbs provide better low end torque, throttle response and fuel efficiency. That is why they make spreadbore carbs with smaller primaries.

Is there a reason why you chose the 5 mpg at 75 mph goal? Will you be doing a lot of high speed driving (and believe me 75 mph is really high speed with these old trucks without a lot of modifications to the chassis, suspension, brakes, etc.)? Most of us drive our trucks around town or at least under interstate highway speeds with lots of starts and stops. If better fuel economy is your goal then it would be better for you to choose a goal at much lower speeds. Your high speed goal will compromise your low speed efficiency.

 

I've taken a few trips with my F1 on Colorado interstates, and on long tips I've gotten from 18-19 mpg. Most tank fulls with mainly in town driving are in the mid 15 mpg range. That's a close to stock v8, 600 cfm ebrock carb, 3.55 gears and 5 speed od trans. I run 70 to 80 on the interstate, which is 2300-2400 rpm. Wind noise is the limiting factor, the truck will run 90 easily. I like the ebrock carb, but I think the gear you've got is going to limit your mpg. I'd like to have fuel injection, but the difference between a $300 carb and a $2000 FI would buy a lot of gas.

 

without an overdrive and / or a numerically lower gear the only way your likely to get another 5mpg out of it is down hill in a vacuum . smaller carb as mentioned will help , and improve the daily driveability , upgrading the ignition will help as also mentioned . i wish my 53 , with a flathead got 12 mpg ................... 8 to 8.5 in town , much worse on the road ........ my 52 customline with a petronix kit , a large bore holley 94 , with a standard old three speed , and it has about the same aerodynamic efficiency as our trucks , gets high teens in town and 23 -24 on the road as long as i keep it at 55 and no more . it has a 3.45 gear i think . got an 8.8 to stick in the 53 with a 3.08 gear when she goes back together for a hopeful improvement in mileage , and i'd be pleased with 12 , and hopefully i can run 65 for more than a millisecond without her sounding like she's gonna blow !!!!!!!!!!!!!!!!!!

 

He's got an AOD, guys. I think he's OK on gearing, or close enough.

I'd look close at the carb, like said above get the build sheet for the list number and see if someone has fooled around with jets. I've found lots of carbs that someone has jetted up because "more gas is more HP"...

 

Hey I live in Pekin and work in Peoria!
I think you would be a candidate for the factory EFI swap from a late 86-93 EEC IV system.
I am working on this type of EFI. I can't say I know everything but I am in process. email me from here or PM me.
It's nice to have another guy from around here!

 

Hey Jeff , I know quite a bit about that system . I was into the mustangs for a long time , and have been over every inch of them quite a few times . If you run into any issues and need any help , shoot me a pm .

Yes , op can change over to the eec iv fuel injection , but he may be killing flies with a sledge hammer in a sense . He can probably get pretty close to the same efficiency using the correct carburetor , and a good ignition system .

I know its not as fancy as a double pumper , but for a stock 289 in a truck , the ONLY carb I personally would be using is a 500cfm 2 barrel holley . You may lose a couple top end hp , but your gonna pick up some low end torque . If your not drag racing it anyhow , then its a great carb .

As others said , we need your list # off your holley to be able to tell exactly what you have . And the eev iv fuel injection is a cool upgrade , but thats if your looking for an upgrade . I wouldnt do it with the sole intention of mpg or you may be disappointed .