351 ** fuel mileage

[bulldawg1081]

my fuel mileage is HORRIBLE!!! its getting like 7 or 8 mpg in town and i drive easy,i know its gonna need a tune up but what else could i do to improve it? how would an edelbrock 600 cfm carb effect it as compared to the stock holley? anything you could recommend would be appreciated,or what about just dropping in a 302 that i already have?

 

[Seabronc]

Not a whole lot, maybe buy a Toyota :lol: Sorry just couldn't resist that /emoticons/[email protected] 2x" width="20" height="20" /> Well start with a good tune up. A Holly isn't known for gas mileage, that isn't what they were thinking about when they designed the Holly. As you can see by my signature I have a Holly and I get between 10 just putting around and 13 on the road. There are definitely ways to improve the mileage with a Holley, but you need to know Holley carbs to do it. If you want to learn more about that subject you will need to get some books. Other than, how much stuff do you carry around that you don't need. Put your truck on a diet, if you are not off roading much remove the transfer case guard and just put it on when you are. Get rid of the ton of stuff in the back, keep your foot out of the carb and let the cruise control drive it on the highway, it is less spastic than a human on the gas pedal.

Good luck,

>-

 

[bulldawg1081]

what about replacing the smog ridden intake with one from edelbrock and add a 600 cfm edelbrock carb?...will that help any?

 

[Justshootme84]

Just my opinion, the stock Holley 4180 4-bbl carb on the 84-86 351W H.O. is a piece of junk, and you would do way better with an aftermarket intake and 600-650cfm carb. In an attempt to remain smog legal, I replaced the orignal, leaky 4180 on my 84 Bronco with a reman unit for about $300. When it was running right, I would get 11-11.5 mpg on the highway and city combined. That was much better than the 7-8 mpg I was getting with the old carb, or when the reman one wasn't working right. Most of the time, the problem was with the electric choke power supply falling out. IF the choke isn't working right, you're mileage will suffer. A good replacement is the Edelbrock 1406 carb, and either the Edelbrock Performer intake or Weinand Stealth models. JSM84

 

[rednck7736]

My 85 had the orginal holley from the factory on it.According to the window striker we had with it .It was suppost to get 12 on the Hwy and 10 in the city.When we git the truck it had over 100,000 on the 351w. H.O..I believe it averaged around 11.5.It was drove easy .It had all the smog stuff on it.But it was disconnected.The old holly went out so my parents replaced it with a 600 elebrock.Had the same gas milage or a little better.But it ran better.

I bought it from them and bought a new weind stealth in take.It has better rpm range and is cheaper than an elebrock.I junked all the un neccary dry rotted vacum lines that were not needed.I was averageing 11 miles per gallon before I pulled the 351 and stroked to to a 427.I have not filled up yet to see how far I can go on a tank.**** it will brank teh bank to fill it.It has a 33 gallon tank.

You can check all your vaccum lines for leak.That will drop wyou gas milage to.If there is a leak somewhere.

 

[bulldawg1081]

thankyou jsm84 & rednck7736 for the replies...whats your opinion with going with a 302 that i have? its an '85 model aswell but is fuel injected,i would make a carbed engine out of it if i used it which im unsure as of now...my friend had a 302 bronco and claims he would get 18 out on the highway....are weinand intakes better than edelbrock? ive heard good and bad from both

 

[Justshootme84]

if you look at the engine specs for the 351WH.O. and 302 EFI, there is little difference in Hp & torque. So if you swapped over to a fuel-ijected 302, you might not notice much loss in how it takes off from a stop, runs down the road, etc. You might get a mile ortwo more per gallon. You could convert the 302 to carb with a new intake and carb, but it would be more work to convert the fuel system to EFI. Just my $0.02, if the current 351W H.O. is running, I would keep it until it breaks down. I wouldn't do the work to swap out motors unless the one you have in the Bronco is broken. I swapped to a 460 when my 84 351W H.O. blew up (bent 2 connecting rods). JSM84

 

[bulldawg1081]

did you have very much of a fuel mileage difference from the 351 to the 460?

 

[Justshootme84]

I haven't driven the bronco enough since installing the 460 to get a milage estimate. But I'll be lucky if i get 10mpg. It's a trailer queen and offroad-only rig now.