351m,hesitation

[rescue43]

Need some help.(please). Ive bought this 79 bronco w/ a 351m all stock. It had a dead spot when i would accelerate and it would not stay running at a intersection and would not idle in the morn. i replace the carb with a stock motorcraft 2bbl. The hesitation actually got worse, had the carb. reset and adjusted chock working ok ( i think) still had a bad hesitation when i get on the gas, to the point if i stay in to the hes. it will stall out, changed the dist,rotor,cap,plugs wires and fuel pump. The only thing iam not positive with is if the vaccume hoses are all proper and in place, not all the hose are hooked up i was told that the ones that are will be the only ones i need ?? cant find a diag. that shows all the vaccume lines from the 2nd dary can. I really hate that hesitation, Iam a capt. for our local fire dept. and when i have to ( ( go i have to go.. especially in the am LOVE my bronco need some veteren help.. Mike from the poconos

 

[Seabronc]

I would go thru the entire timing proceedure first. That proceedure should be listed on the Vehicle Emission Control Decale. I am not sure where that decale is located on a 79, but on my 83 it is to the left of the hood latch. That decale also shows the vacuum line schematic. The only vacuum line that should be critical durring the time you say you are experiencing hesitation, is the one from the carb to the distributor. Usually that line is connected to the port on the passenger side of the carb near the top. However, different calibrations sometimes hook it to one of the ports under the carb generally located on a spacer plate.

By stock carb, what is the modle number? I have an 83 shop manual that shows several different carb modles and It may list yours since they keep stuff like that the same for several years.

Good luck,

>-

 

[Seabronc]

PS,

Another possibility is the mechanical or vacuum advance mechanisms in your distributor.

Vacuum leaks that will **** you. Use propane and a friend to find a leak. Open a the valve of a propane torch and move it around the carb base and vacuum hoses. If the engine speeds up, you found a leak. The friend holds a fire extinguisher, just in case. It is a common proceedure and not a high danger of fire, but you know about that stuff

Good luck,

>-

 

[4xfan78]

If you do not have emmission laws where you live the best thing to do is replace the 2 barrel card and intake with a 4 barrel (Edelbrock) carb and intake. The power will increase and you will get better mpg's as long as you keep you're foot out of the gas.

 

[rescue43]

thanks for the propane trick and i have been kicking around a 4barrel, last night i put a clear fuel filter at the fuel pump and it immediatly filled with rust from the tank, cleaned it out and tried it again and within seconds it was semi clogged again, I think it might be time to replace the tank, thinking of jumping up to the 33 gal. replacement tank. hope it will fit.. thanks to all of the advice, if i have any other questions i will ask,, thanks again... /

 

[4xfan78]

Lmc truck has the plastic replacement fuel tanks for $120.

 

[Billz4x4z]

I for 1 don't like pollution equip.I would find an older carb adaptor that woul eliminate egr plate,eliminate all vacum lines except for the 2 that are necessary,3 if you have auto trans.1 vacum line from the vacum port just below the choke to the dist.,1 vacum line from the brake booster to the port on the back of the intake,and if needed from vacum modulator on the trans to port on back of the intake.tha eliminates all the other garbage.Also try advancing the timing.I found by doin the above I got better throttle response and better mpg.

 

[Ziggy]

I would drop the tank first, clean it out and see if it is salvagable. If it is not, then replace it. If you don't already have a 33 gallon tank installed, you will first have to find the skid plate for the larger tank as this is also what holds the tank up. The 25 gallon tank straps will not work. Also, your rebuilt carb may not be set up for your Bronco. I ran in to this when I replaced my carb, I ended up rebuilding it in order to get it to run right. I agree with BillZ in removing all the emissions crap if you can get away with it. The only thing I left on was the EGR plate, and that was just so I could mate my carb to my intake. I still run the 2150 carb on an Edlebrock intake and cam set up, but I'm looking for torque, not speed and the 2 BBL carb works fine for me, plus my gas milage is still up around 12-16 mpg.