I have a 76 F-250 w/ 360 2bbl with headers and the four speed w/granny low also 4:10 gearing. the problem is that i am only getting 6 miles to the gallon city and 8 highway. i talked to my father and he sayed he used to get 12 mpg with his (same set up) i think the carb is over jeted and am planning on putting a edelbrock aluminum intake and a holley 600 cfm 4bbl hopefully gets better mpg.
I can't see it getting any worse. And telling your wife that these performance parts will give you better mileage is fair - and might even be true if the parts you are replacing are defective.
If you want to improve your mileage buy a vacuum gauge and do a good tune up on your engine. Make sure you have good wires, the vacuum advance works and everything is adjusted right and that you have good vacuum at idle.
If your carb has too big a set of jets, buy a smaller size. Wouldn't hurt to rebuild the carb - but just getting the jets right will help.
You are geared too low for really good mileage on the highway, but you should be able to get 12. I get 15 out of a F250 with a stock 390, running a C6 and 354 rears.
i am not surprised since you have 4.10 and a camper special. I have a 1979f150 4x4, 390,4bbl, c6, 3.50s, duals exhaust and i get the same mileage as you. I ran a long trip this winter and with a couple wot races in there i got 8.12 on the highway only. The truck may be capable of 9 mpg in the fall with a tailwind. I do think the 4bbl could help you as the primarys are smaller. Hell i bet electronic ignition will benefit you. Just steal a duraspark setup and install.
v is for venturi also called 2bbl or 4bbl. It doesn't mean valves. Todays modular motors it is the amount of valves per cylinder 2v, 3v ,4v but they typically add them all up when saying the motor like 32v 4.6 dohc cobra motor.
Not a stupid question - we all are looking at gas mileage nowdays. And I have found that a well performing engine will give you both - power and gas mileage. If your engine is tuned correctly your milage has more to do with how you drive then anything else.
I would not put up with 6 MPG around town if for no other reason then the time lost always filling the tank.
octane boost is scam! been there done that and researched it. There was an interesting thread a long time ago about them. I think it was sunoco who did the tests. I would do a search for it. If you don't know sunococ makes racing gas and is nascars supplier.
I did some research and a store bought bottle of octane boost will only boost the octane 2-3 points i.e. 91 to 91.2. Not really worth it. The usual ingredients are Toulene, Xylene and Methyl-tertiary-butyl-ether (MTBE). I think MTBE was outlawed? Anyway, one would have to mix to 10, 20 or 30% ratios to get any real results.
Bottom line: A little bottle of that stuff won't do the trick.
BTW: Bad gas milage+ FE engines= a fact of life
Last edited by 71_4x4_390; 02-24-2005 at 07:37 AM.
I agree, FEs don't get the best mileage. But. my high performance stroked 428, running a C6, Dana 60 with 4.10s, and 30 inch tires netted 10 mpg on the highway. So, he ought to get a little better than 8mpg.