Need some help on my 1984 F150 2WD 351 HO. I picked up this survivor a couple of weeks ago. has 132k miles and is in all original condition. It starts right up, idles great, sounds great, has excellent oil pressure, however, I noticed that on acceleration, it hesitates and stumbles. I have replaced plugs, wires, cap and rotor , but it still stumbles. I've read that it is probably the carburetor. It has the original Holley 4180 and I am considering replacing with an Edelbrock 1406. Would this work, and what issues should I look for when I tackle this swap?
Thanks in advance for the help.

 

If you are going to swap the carb to something else avoid the Edelbrock if you have an auto you need to buy the adapter kit separate, reroute the fuel line etc etc. Either opt for another Holley or one of the Summit M2008 carb's.
Also swapping the carb to a non emissions style carb will mean modifying or removing some of the emissions equipment.
The carb is very likely due for a rebuild so you also have the option of rebuilding the original.

 

If you are not up to rebuilding a carb, a new one is probably your best option. But as was mentioned, a aftermarket carb will need a few modifications to make it fit, even a another Holley. Everyone has their opinions on carbs, I gravitate toward the holley's myself since that is what I am more familiar with, but if you want to run a Edlebrock, it would work fine also. Most important thing, make sure you put a good fuel filter on it. Your stock carb probably has the filter screwed into the carb, the aftermarket carbs usually require a external filter in the fuel line, so that is part of the minor modifications you need to make.

 

 

 

Thanks to all for your input. Sounds like I have some work to do. I did pull the vacuum line off the EGR , capped the port and plugged the line. Truck ran exactly the same as when connected. Probably start with a new EGR. I'm pretty sure that the carb is original and could use a rebuild. Thanks again for the help. I'm sure you'll hear from me again soon. I'm mechanically inclined, but I ain't a mechanic.

 

Maybe hold off until we hear back from some others. My memory is fuzzy, but I could have sworn the EGR test is a little more involved. Don't quote me on that, however. Something about needing a certain amount of exhaust pressure to seat the valve, but now I'm doubting myself.

I'd also suggest checking fuel pressure and volume. A problem there could cause a stumble .

 

The cheapest and easiest thing to do would be to simply rebuild your existing carburetor.

The Motorcraft (made by Holley) 4180 you already have is a good carburetor, and better than an aftermarket Edelbrock carburetor, in my opinion. It is the same carburetor that the mighty Mustang GT 5.0 used from 1983 - 1985.

 

 

Stumble on acceleration is most likely a accelerator pump problem in the carb. If it was a EGR problem, it would idle terribly if at all. It's very diffcult to mask a leaky EGR.

You can check to see if the accelerator pump is working properly and check it off the list of possibilities if it is working ok. All you have to do is pull the aircleaner off, and get a flashlight and crawl up in the engine compartment or get on a ladder and lean over the top of the carb. With the engine off, pull the choke door open if it's in your way, and shine the flashlight down the throat of the carb and push the throttle wide open. You should see two strong streams of gas pour into the throat of the carb with some force behind them. If they are weak and just dribbles, that is your problem. You can let the throttle back closed, and then push on it ever so slightly, and you should get squirting with the slightest movement.

You can mess with this about 3 times, but after that I would quit, since you will flood the engine moving the throttle too much without it running. No harm will be done, but it will make it hard to start afterward.

 

 

The secondarys should be moving fuel all the time, the secondary throttle plates should not be fully closed if adjusted properly and will move a bit of fuel even at idle.

 

This is the first thing you should do as this is a sure sign of a accelerator pump with a weak or no squirt.
If it is the cause I would rebuild your carb and go from there.
Also rebuilding yours there is no messing with vacuum lines that need to be plugged, other brackets to get the auto trany to shift right, fuel lines re-routed, etc.
Dave ----

 

Wow! Thanks everyone. Not only getting some great advice, getting educated. Once past the hesitation, she'll open up and run, pretty quick too I am hoping its just a carb rebuild. I'll give these suggestions a try tomorrow. Off to watch football now. Thanks again. I keep ya'll posted.