4 replies to this topic

[84AZbronco]

I recentley purchased a 84 full size bronco.(351) (2 barrel motor cafrt carb) I was was aware this big rig would not get the best gas millage on the road but what i have experienced in my first couple of tanks is outragous. I was always told to expect about 12 mi a gallon. my first full tank i drove till i ran out and it turned out to be a little over 10 mpg. but in my last couple tanks its been coming out to more like 8. my engine is re-built with less than 5k mi on it. my tires are well inflated, the spark plugs and air filter are realitivly new and clean and i regularly use the fuel system cleaner. I can not figure what would kill my gas milage so bad. there are no gas leaks or hloes in my mufflers as far as i can tell. there is one verry small hole at the verry end of my left exhaust pipe right where it curves 90 degres to the left but besides that the rig has no obvios problemes. im looking for sugestions for posibilys to hidden things that can kill my gas milage. perhapse the card is just sucking to much gas and needs ajusting? any oppions and suggestions welcome! also i curunly have 31 inch tires and want to get some 33's will that size tire rub with no lift of any kind? thanx , 84azbronco

[Broncoholics]

Do you know the CFM on your carb? I like 4 barrels myself with small primaries for milage and larger secondaries for power. The problem here is the secondaries will really suck the gas if you have a lead foot. Try a 600 cfm single pumper Carter Carb I found it to be the best out of the box, no adjustments. Edelbrock is OK for milage too, most have same size primaries and secondaries so the milage stays consistant. Most others seem to suck the gas from my experience.

When coasting does the truck slow down quickly? try it in nutral to see if something drags like a brake.

Adding 33's should fit and might help gas milage if you do lots of freeway driving. Once up to speed the RPM's will be lower at freeway speeds with larger tires which will help. In town use might get worse due to off the line power loss with larger tires but not much.
The 33's will fit the rear no problem. The front might need a 1" lift coil. Some mfg's sell them if you use a snow plow, winch, heavy bumper or want to level the truck.

[highboy73]

he's right about the 4bbl carb the smaller primaries do help as long as you can keep your foot out of it,I had a dramitic change in gas mileage when I changed to a 4bbl(holley 600).especially on the highway.
check your timing,fuel filters,pcv valve,the works go thru it all.
I always do one thing at a time and see what if any diff it made,and as always I start with the cheapest simplest stuff.
I'd check the brakes for a drag like broncoholics said also.
is your 4x4 disengaged?something to check.

[orich]

I recentley purchased a 84 full size bronco.(351) (2 barrel motor cafrt carb) I was was aware this big rig would not get the best gas millage on the road but what i have experienced in my first couple of tanks is outragous. I was always told to expect about 12 mi a gallon. my first full tank i drove till i ran out and it turned out to be a little over 10 mpg. but in my last couple tanks its been coming out to more like 8. my engine is re-built with less than 5k mi on it. my tires are well inflated, the spark plugs and air filter are realitivly new and clean and i regularly use the fuel system cleaner. I can not figure what would kill my gas milage so bad. there are no gas leaks or hloes in my mufflers as far as i can tell. there is one verry small hole at the verry end of my left exhaust pipe right where it curves 90 degres to the left but besides that the rig has no obvios problemes. im looking for sugestions for posibilys to hidden things that can kill my gas milage. perhapse the card is just sucking to much gas and needs ajusting? any oppions and suggestions welcome! also i curunly have 31 inch tires and want to get some 33's will that size tire rub with no lift of any kind?  thanx , 84azbronco

Hi I'm a new guy in here. I A'm a old ford guy, That gas hog bronco may just need too be rejeted. No big deal. remove carb top & float and there's the jets. This all depends where you live. Dry or wet high in mtns. or at sea level. This is old school stuff now! Do it by reading the plugs. And remember lager tires will throw off your speedometer so you maybe getting more mileage than you think. You maybe driving it faster now the newness is wearing off a bit or a big change in the weather from damp to very dry can play a part in mileage. Damp or raining weather you'll get a better burn from you gas =runs better can add to milage.
Hope this helps in some way. my 2 cents
orich

[mockdaddy]

my question is, how are you figuring gas mileage? is your speedo off with the taller then stock tires? That will effect the odometer too. With larger tires the speedo reads at a slower speed due to the circumfrence of the tires. one - two miles per our will make a big difference over a tank of gas