TXDIPPIN 1993

Whats up guys I am new to old school engines don't know whole ton about carburetors and I just bought a 1980 Ford F 150 Ranger and it has a 351w and when I bought it the guy said the carburetor and needed to be adjusted and unfortunately its winter down here and I know carbureted engines have trouble starting in the first place just because it's cold so I don't really know how to go about it adjusting the carburetor what I need to look for or if it could be something else because the truck has no ***** whatsoever it's just sluggish and it has true duals on it with factory manifolds from what I can tell and he stopped the exhaust off just before the muffler so its straight pipe essentially could I get some help on what I should do to get this truck back to its former self

burnthelight88

If you know what carb it has, let us know. Otherwise, remove the air cleaner and take a picture from a couple angles.

Adjusting a carburetor isn't all that difficult, but for best results you'll need a tachometer and vacuum gauge. You need to be able to see these while under the hood. I do mine without the tach but you definitely need the vacuum gauge.

In reality though, it almost surely needs rebuilt. Not a difficult project, but with some adjustments you may be able to get through winter. A properly tuned carbed truck isn't any harder to start, its just that most of them arent tuned.

If its feeling sluggish and you just got it, I'd start with a tune-up... plugs, wires, cap & rotor, fluid changes. Always a good start.

TXDIPPIN 1993

Sweet thanks man that helps out alot I'll post a picture of it in this thread and I have another question about the AOD transmission in my truck doesn't have a fourth gear or so it seems I looked under the truck and the TV linkage and everything looks normal from what I can tell and it still has some spring in it so does that mean that my 4th gears just burned out

burnthelight88

Start a new thread or do some searching to find out about that transmission issue, I've never owned an automatic in a truck this old.

As far as the carburetor, that is the Motorcraft/Autolite 2150. Its pretty much the most common carb on these trucks and you'll find rebuild kits and information on them to be plentiful. Again, I would rebuild the carb, but if you need it adjusted for a while before you can rebuild it, I'll cut and paste the best write-up I've ever seen on it.

Even if you aren't going to rebuild it right now, some of these adjustments are made much easier with the carb off the truck.

burnthelight88

If the carb is staying on the engine, check the wet height of the float. Start the motor and let it run until it's at operating temp, and remove the air horn from the carburetor to expose the fuel bowl. Measure the distance from the center of the fuel level to the top machined surface of the fuel bowl, and this is the wet height. The rebuild sheet will specify what this height should be. If your measured height does not match the specified height, you must remove the float, bend the tang, and start over. Don't forget to snap the float retainer in place when you replace the float.

Be careful when you remove or bump the float, as fuel will spray out of the needle. Also be careful when doing this check, because you have an open fuel source and a running motor. Do this step correctly, and we can take the float out of the picture. Don't waste your time playing guessing games when working with carburetors. Take the time to do things right and do them once, and you won't have problems.

Here is how you take care of the choke and fast idle issues. Once again, proper procedures dominate shade-tree trial-and-error time and time again. Please read my instructions carefully.

Choke pulloff clearance. When you get in any carbureted vehicle to start it first thing in the morning, you push the gas pedal once to "load the choke." This snaps the choke plate shut all the way. Because it's just a spring, its job is to tighten itself. It can't accurately control "how much" it tightens. If we just let the choke pull the choke plate all the way shut when you first start the motor, there will be no way for air to get into the engine. Therefore there is a "choke pulloff" which serves to slightly open the choke plate against the choke spring tension, just enough for air to pass in. The vacuum created by the starter cranking the motor pulls the pulloff diaphragm and lets that first sip of air through.

To adjust the choke pulloff, the motor must be cold and shut off. Loosen the 3 choke cap retaining screws and rotate the choke 90 degrees toward the back of the truck to completely shut the choke. Then, find the choke pulloff vacuum motor on the rear passenger side of the carb. There is an arm coming out of it which actuates the choke linkage. Press the arm all the way in to simulate vacuum pulling the diaphragm, and the choke plate should open slightly. In your rebuild sheet will be a "pulloff clearance" specification and it will be something like 3/32" and such. You must take a drill bit of this size and insert it between the rear of the choke tower and the back-end of the choke plate, to measure how far it is open. It acts like a feeler gauge. There is a small set-screw in the back of the choke pulloff. If your pulloff clearance is not to specification, you must adjust that screw and start the procedure over.

Fast idle index. While the choke is engaged, there is a mechanism to raise the idle above curb idle because the enriched fuel mixture requires the engine to run at a higher RPM. There are two settings for this - fast idle speed, which controls engine RPM during this time, and fast idle index - which controls how much of the choke engagement time that the linkage actually contributes.

When things are functioning properly on a Motorcraft 2V carburetor, there are 3 stages to startup - start, fast idle and curb idle. A small cam on the passenger side of the carburetor has 3 steps and controls this. When you first start the truck and you load the choke in the morning, the engine starts at its highest possible RPM and the throttle linkage is on the first step of the cam. When you bump the gas pedal again, the fast idle linkage is released and allowed to drop, at which point the throttle linkage is on the second step of the cam. The throttle linkage remains on this step of the cam for the entire length of time the choke is opening. Once the choke is completely open, the cam drops out of the linkage completely and the carburetor returns to curb idle. This is where the engine remains for the rest of the driving until the engine cools down again the next morning, and the process starts over.

To properly idle during warmup, it is imperative that you sync your choke with the fast idle cam. Again, there is a factory procedure for this. If you're with me so far, your choke cap is still rotated 90 degrees from when you were setting the choke pulloff clearance. Here is where to go from there:

1. If the choke isn't rotated toward the back of the truck already, do so now.
2. Open the throttle, and hold it there with one hand.
3. With your other hand, push the choke pulloff rod in all the way, the same way you did in the pulloff clearance procedure. The choke should now be open in the pulloff position.
4. Your other hand is still holding on to the throttle. Let go of the throttle, so that it rests again.
5. Now the important part. Look down at the fast idle linkage, underneath the choke cap on the passenger side of the carb. There is a small cam above the throttle shaft. You will see a small V notched onto the second step of the cam, and you will see a long screw with its tip touching the surface of the cam. The tip of this screw must be aligned perfectly with this V. This is the measurement Ford uses to tell you that you've set the fast idle index properly. If it is not aligned with the V, there is a small hex screw on the plastic fast idle arm in the linkage. You turn this to adjust the index. Each time you adjust this screw, you must start this procedure over and check for alignment.
6. Note that anytime you adjust pulloff clearance, you must adjust fast idle index. This is why I had you check the clearance first, before doing this procedure. Make sure one thing is right before you move on to the next.

This configuration gives the following results: when you first start the engine, the idle is high. Once you get out of your driveway and start driving while the engine is still warming up, the idle is still high, but not as high as when you first started it. Once the truck is warmed up completely, the choke is open and the idle returns to normal.

Fast idle speed. Once your fast idle cam is properly aligned, you must adjust the speed at which the engine idles when the fast idle is engaged. You will notice that under fast idle, the throttle plates are open further. I usually adjust this to allow the engine to run at a 200-300 RPM higher than curb idle. Contrary to most of my statements in this post, this adjustment can be trial-and-error provided the linkage is working in the first place.

Choke cap index. If you're still with me, the choke cap is rotated toward the back of the truck. Now you must align it properly. On the rim of the black choke cap is a small notch. On the metal choke housing to which it attaches are seven notches. The goal here is to align the notch on the cap to one of the seven notches on the housing. Going from the back of the truck toward the front, the notches are represented as 3 Rich, 2 Rich, 1 Rich, Index, 1 Lean, 2 Lean, 3 Lean. On the emissions label attached to your hood or valve cover, it will say which notch to align the choke to. If your label is long gone, 1 Rich is usually a safe ball-park figure. This adjustment is often changed during winter and summer season changes. While you're doing this, this is a good time to make sure the choke spring is properly engaging the choke linkage tang inside the housing, as this is often overlooked during a carb rebuild. Once you have the choke cap aligned, tighten the three retaining screws back down.

If you follow the procedures above, your choke and fast idle will be set properly. Like I said before, proper carburetor performance comes from closely following proper procedures, not making guestimates. Ford engineers marked these carbs with all sorts of notches and numbers for a reason - so that they may be tuned properly.

GhostriderI

Outstanding write-up burnthelight88, one note: I was taught (by a master mechanic in the '70s) to set the fast idle on a warm engine as the last step after the choke cap was tightened, then double check and set as required the curb idle. Other than this note it was real close to same procedure. Also other than the wet height in the fuel bowl and the idle settings, these can be done installed (with the correct tools because some of these adjustments can be in awkward places) or on the bench.

Hope this helps

burnthelight88

Ha yeah I lack all of those "right" tools usually and the first time I did the adjustments it just helped to have it right in my face. You're right though I did end up having to make some slight adjustments once it was back on the truck

TXDIPPIN 1993

Brunthelight88 thanks again for all the info you provided man your the best! I was reading my owners manual that i found in the floorboard and it doesnt list a 3 speed auto with overdrive so i i guess its just a 3 speed so that solves that problem. But i have a couple more questions. How hard is it install headers on these 351s and will long tubes give more low end? Can i go to a four barrel with stock heads valves and cam? And do i have a flat tapet cam and how hard is it to upgrade to roller set up

GhostriderI

The "right tools" I was talking about were these

sorry pic is so big

TXDIPPIN 1993

Thanks ghostrider do you know much about cammin these old engines and how hard it is to install headers