I was thinking of buying a 86 f150 for my son, and I think it has a 4 barrel holley on it, how do I disconnect the 4 barrels on it, and what adverse effect will it have on the driveablity. would running just the 2 barrels make alot of diffence in fuel mileage?

 

You would be better off buying a two barrel or smaller four barrel carb sized for his intake and swapping them out. Four bbl carbs have two primary and two secondary barrels. If you disable the secondaries, you most likely will not get enough fuel flow to operate properly and the truck will run like crap instead of just not running as fast. Without enough air flow to run efficiently, fuel economy can suffer worse than running four barrels.

What size 4 bbl is it? A 600cfm or a 750cfm or what? What motor? I had Holleys on two trucks, a 460 and a 390.

 

I have an '87 F150 4X4 with an 351W. It came from the factory with a four barrel Holley rated at 600 cfm..(4180C ) Ford trucks with factory holleys will not let you change to a regular four barrel holley.. I tryed to do just this and found out the hard way.. If you try to put another Holley on the linkage will not let it open all the way.. I ended up changing to an Edelbrock that happened to have two different sets of bosses on it for the linkage.. One set let you use the factory carb, the other set let you use a different Holley or ?? But what the heck, why not just let the kid have the four barrel.. Just put in a black spring on the secondarys and that should help keep them closed most of the time..

 

Yea, I'm with thrillseeker, to some degree. If you change the spring, make sure they don't all of a sudden flip open at 4500 RPM. I had mine set up like that and it made for an entertaining surprise on wet pavement.

You should be able to pull and block or otherwise disconnect the vacuum lines or line. And you may be able to block or wire the secondary linkage.

Do not try to limit throttle travel, as the primaries must be able to go wide open and operate the tranny kickdown etc.

Make sure the throttle operates smoothly and returns properly.

I disagree with Rocky--the primaries are jetted on their own and the engine should run fine on them alone. It should still be able to get to 4500 or better--just not as fast.

In any event, you can do this and see how it runs. If it runs poorly, go to the more complicated and expensive step of swapping to a 2V.

You won't save much money as the cost of doing that will buy the difference in gas for several months if not a year.

Mileage is going to depend more on how it's driven--if he's running the primaries wide open all the time, he's going to go through almost as much gas as if the 4V's were open. In normal driving, maybe 1 or 2 mpg.

 

Moved to proper forum.