Awesome, thank you. I was actually currently reading one of those myself, lol.

 

yeah the search function on the forum is great lol i have been on here a while and just found it a few months ago lol...

 

I'll see if I can help you out with a few of your questions, first off, I think was you mean by a non- EGR is one that isn't computer controlled, and all that, right? Go to your local junkyard (if your going to own an old truck, you'll get to know the local 'yards' real fast!) and find a truck with the same engine, but 1983 or earlier. Pull off the carb of it (only two or three nuts hold it down, it's real easy) and buy it. Some yard will pull it off for you, but they usually like to charge for that. Go to the local parts store and show it too them and tell them you want a carburetor re-build kit for it, it'll only be about $20. Then check back here and we'll help you out with that.

You'll have to swap in the dura-spark 2 distributor and ignition box to get the motor to run with it's "new" carburetor, but it seems like the other guys are covering that pretty well.

And for now, don't bother about the 'headers' and exhaust pipe. Currently your truck has a cast iron manifold- not much goes wrong with that! Just check the exhaust pipe and as long as there arn't any holes in it, your good! Headers are mainly a power upgrade kinda thing- they are more efficient at moving exhaust out from the engine- so it would make a few more horsepower with them.

I would suggest going to the local book store and buying a few old reader's digest auto repair books (looks for the OLD ones, from the 70s or 80s) They're great stuff and designed for the beginning home mechanic- they've saved me more than once!

Sam

 

I think I understand where you're coming from... All I can really do is suggest research.

Google is your friend here. Look up how Carburetors work (they all work off the same general principle)
Look up how distributor's work... They also pretty much work off the same principle.

Honestly though, the fact that you're willing to admit how much you don't know puts you ahead of about half the less experienced people I've seen.

 

As pointed out, DS2 stands for "Duraspark 2" ignition system. It is an electronic (breakerless) system that Ford used from the mid 70's to the mid 80's, and is considered to be among the best *factory* systems ever made. It was phased out during the 83-87 time frame, and replaced with the TFI (thick film ignition) that your truck *should* have.
DS2 uses a fender mounted control box and a dist with a vacuum advance and 3-4 wires at the dist.
TFI uses a dist mounted control box, no vacuum advance, and 6-8 wires at the dist. All timing advance is controlled by the computer, thru the TFI module. This is why it must all be intact, or the system goes into "limp" mode. Limp mode will still get you around, but with far less power and MPG than if the system is fully functional.
83-86 F150's that came with the feedback system and TFI ignition, were also factory "pre-wired" for the DS2, since it was used on most V8's thru 85, and still on some 86 V8's. This makes the carb/ignition system a relatively simple swap, if the feedback system is hacked up.
Like others have already pointed, there are numerous threads that detail the swap, if needed.

 

Honestly, I wasn't even aware that there was a computer in this truck. I would think that 1986 seems very old for a computer in a vehicle, although I imagine it's nothing like a computer in the traditional sense. When I say EGR (and I hope I'm using it correctly here) I'm referring to the type of carburetor that has all the hoses and tubes coming off of it that hook up to... something.

It was originally explained to me that the EGR system had something to do with emissions and that mine is neither needed nor working so I might as well phase it out when I replaced the carb.

Is the DS2/ignition overhaul required for any carburetor upgrade or is it specific to the pre '83 carb from the same engine? The reason I ask is because in a lot of the stuff I've read, people have gotten very good results with upgrading to a larger/more powerful carb and this is the direction that I was leaning. If I bought a new carburetor, would I still need to do the DS2/ignition change?


Great info, thank you =)

Thanks. I've really been reading a lot over the past few weeks and days especially. It feels overwhelming at times and I feel like I just need a little direction and a starting point. I read the wiki article on carburetors and have a much better understanding of what they are and how they work. I think I'm going to read about distributors and ignition systems next as it looks like I'm going to need to do the DS2 thing.



Is my truck having a TFI something that I would need to verify before I begin? If so, how would I do that?

I'm 90% certain that my truck is in limp mode. I can tell it's much more powerful than my car (99 accord, woop woop) but it feels a little weak and I got single digit mpg on the way here from Georgia. I don't want to talk about that gas bill =(

Awesome info. Can I do the DS2/ignition swap before I upgrade my carburetor or is this something that needs to be done all at the same time? To be fair, there's not much that isn't hacked up on this truck. It is my understanding that it was formerly a farm truck and you can really tell. She's not pretty to look at and half the stuff in the engine compartment has been cut/spliced/hacked/shorn or whatever other descriptor you want to use. I figure it's about 20 years behind on routine maintenance... lol.

Again, thanks all for the great info.

 

Followup question. Is the DS2 Ignition system something I should buy as a preassembled kit (is this even possible?) or will I need to go to a junk yard and pull one out of a car?

 

You asked for info on carburetors and while I'm not an expert I know my way around them.
The carb mixes about 15 parts of air with 1 part of gasoline to produce a mixture that will burn when ignited by the spark plug in the cylinder. The engine is really an air pump that draws the air in through the carbs throttle body and pulls the fuel out of the fuel bowl by a venturi. The venturi is mounted in the middle of the carb barrel and it is in the path of the air going into the intake on its way to the cylinders. The venturi does a good of vaporizing fuel at a constant engine speed but it needs help as the load changes or the engine slows down and the air flow is reduced.
On non computer carbs the mixture will be enriched when you press on the gas pedal by the accelerator pump which squirts fuel into the intake and the power valve which is controlled by the intake manifold vacuum. Low vacuum will flow more fuel through the valve and high vacuum will flow less. When the engine slows down it doesn't move as much air and the venturi won't flow enough fuel so the carb will have a mixture screw circuit that flows more fuel at idle to keep the engine running. If this sounds complicated it is and the carb will have all kinds of small passages with springs and check ***** to control the flow of fuel.
The carb has to hold a certain amount fuel so its available quickly and this is controlled by a float and valve assembly. A plumber friend once compared his Quadrajet to a toilet when I had it apart since it used a float like a toilet to control the fuel level in the carb. He called a Kohlerjet since the 454 C 3500 DRW utility that it feed only got 10-11 mpg.
When a computer is used to control the carb it looks the same but its controlled by an oxygen sensor and its trying to maintain a certain air fuel ratio. Instead of a power valve controlled by vacuum the computer will cycle it. Most computer controlled carbs will have a stepper motor that controls the idle speed. If everything worked as planned the feed back systems would produce out standing gas mileage and the multi barrels carbs on V8s performed quite well.
Carbs are identified by the number of barrels and how much CFM it can flow. Most truck sixes and fours used a single carb with one carb barrel or venturi. (1V or 1bbl)
Most V6s and V8s would have a 2v or 4v carb. Most 4v carbs run mostly on 2v called the primaries but will bring the other two "online" when you floor it. I love EFI but I miss the sound of a well tuned 302, 350, or 440 when the secondaries kicked in.
CFM or cubic feet per minute is how we measure the amount of air the engine is consuming. Most engines have a carb that flows more air than the engine needs in stock form. I had a 302 with a 390 cfm and one with a 500 cfm and the 390 had much better throttle response from idle to 3500 rpm. Once a friends 351 V8 with a 500 cfm carb started leaking and we threw on a 350? cfm from a 302 V8 so he could finish plowing. He liked the smaller carb better for pushing snow.
The 300 six with a 1V carb will perform OK and there some things that you can do that will improve the performance as many of the previous posters have pointed out. There are some great links, info, and plenty of people that will help.
Although the head is the biggest restriction an intake manifold/ 2v carb upgrade, DS2, and EFI exhaust manifolds will probably increase your HP by 30-40 over stock and make it a much more reliable and enjoyable engine. The performance of the stock cast iron intakes and log exhaust are pretty bad on most sixes. The original Motorcraft 2100 2v used on 302s works well on a 300. As stated above the DS2 ignition system works great and the EFI manifolds will flow very well. If you want more its there but the head will have to come off for a good port & polish and rocker upgrade to handle the new cam. That with a 4v carb and long tube headers will get you close or over 200 Hp.

Just my 2 cents

regards
riikard

 

Awesome post; very informative. This is exactly the kind of information I was looking for =). I hope you don't mind I have some followup questions for you.

1. I see a lot of people referring to carburetors as 1v, 2v, 4v, etc. I'm assuming the number corresponds to the number of barrels? If so, should it be 1b, 2b, 4b? Why the v? Does v stand for valve or something other than barrel?

2. After doing some reading it seems that bigger is NOT better and can cause diminishing returns if not be out right detrimental. How then does one determine the appropriate CFM size for their engine?

3. What does it mean when you say EFI manifolds? Is that the intake manifold or the exhaust manifold? I thought EFI stood for electronic fuel injection?

 

First, I really like your attitude and eagerness to learn. You obviously have a pretty good aptitude for this stuff or you wouldn't even know what questions to ask. Be patient, read a lot, and you will eventually know your way around your truck very well.

Check out howstuffworks.com. Back when I had a lot of questions like yours to ask, it helped me understand how all the various systems under the hood of my truck work.

I'll also give you some general advice. Regarding parts stores, be aware that almost anything that Autozone, Kragen, O'Reilly's, or any of the other chains sell is very cheap. And I don't mean in price. Most of the stuff is overseas junk that won't last. And if you want a reliable truck, don't put cheap parts in it. When shopping for parts, look online first. You can get genuine Ford parts cheaper online than anywhere else. There's a user here that sells them, too. Online merchants like Jeff's Bronco Graveyard, National parts depot, LMC truck, etc. are all good sources for parts. You will pay more for better quality parts but it beats being stuck somewhere on the side of the road. Look at it like this - 95% of the parts on your truck are original. They've been working fine for 25 years, which is an impressive feat. Now look at the cheap junk you find in Autozone and tell me if it's likely to last as long. You should already know the answer to this. If a part is too expensive new, and isn't a wear item like spark plugs, filters, etc. then a junkyard is a good place to get them. This is why people have recommended hitting up a local yard for the non-feedback card and DS ignition system. They sell parts cheap, they're reliable (because they're Ford parts) and there are millions of them lying around. A junkyard will probably soon be your favorite place to spend a Saturday afternoon.

From your post, it doesn't sound like you know what the EGR system does or how it works. Automakers are always looking for ways to get better fuel economy. As a result, the fuel mixture is as lean as it can be at cruise. Lean mixtures like this explode very violently and produce a lot of heat. Hot combustion gasses produce a lot of NOx (nitrous oxide) emissions which are bad for the environment. So these clever automotive engineers effectively reduce the size of the combustion chamber by introducing a small amount of inert gas into the fuel/air mixture. Inert gases like CO2 don't combust. They just sit there and take up space. This allows the mixture to lean out without producing a lot of NOx gasses, giving you better mileage and improving the air quality for the rest of us.

So an EGR system is really a good thing. When working correctly, it makes for less pollution, better fuel economy, and since it's only used for partial throttle cruising, it doesn't impact the power of the engine at all. As soon as you punch the pedal, the valve closes and you get a full mixture of fuel and air.

That being said, a lot of people still choose to ditch it anyway. It's your truck, but you should be aware that removing emissions equipment, including the EGR system and smog pump, are federal crimes punishable by fines and/or jail time. I don't know a lot of people serving time for plugging their EGR valve, but there's the warning anyway.

On a truck this old, the vacuum lines and gaskets are all going to be in rough shape. The intake gasket is shot on yours, as you've already noticed, and replacing it is a pretty serious undertaking. As a beginner, you could be in over your head pretty quickly. As soon as one bolt breaks off flush with the head - and on an old truck, one surely will - you are probably going to have to pull the head and take it to a machine shop to have it professionally extracted.

I would start with the little stuff. Change all the fluids, filters, hoses, belts, etc. I would swap the distributor/ignition system out and get rid of the feedback system because it's junk as has already been mentioned. That will probably clear your stalling/no-start problem up.

Last, don't be afraid to ask a ton of questions. There are some super knowledgeable people on this forum and someone probably knows the answer to whatever questions you have.

 

Good question. Wish I knew. Venturi maybe?

There's a formula that you follow. It involve the displacement and the max RPMs then engine will ever see. Too much carb is indeed just as bad as not enough. You have to size it correctly for the engine. I don't know the formula off the top of my head.

It does. Ford switched to different exhaust and intake manifolds when they introduced EFI to the 300 in 1987. The EFI exhaust manifolds are in two pieces as opposed to one-piece carb manifolds. The EFI manifolds flow better and are considered a good upgrade for the carb 300 motor. The intake obviously is completely different because the EFI manifold has a throttle body attached to it (along with holes for the fuel injectors) and the carb manifold attaches to, well, a carb.

 

Yikes! I would never have even thought... That's a bummer. And you hit the nail on the head, I have never really had anyone sit down and explain exactly what EGR is/does. Just to clarify, from your description it sounds like EGR is a completely (or nearly) independent system from the carb? Can I still upgrade to a non-EGR variety carburetor without breaking the law or am I still confused?

My dad did mention something about breaking off bolts, it definitely didn't sound fun. I plan on doing the DS2 upgrade, I think I'm going to make that my major summer project. And just to be clear on that, I can do that without changing the carburetor at all, right? I'm on a college student budget so it's going to take me some time to save up these for these parts. I'll more than likely be doing upgrades piecemeal style.

Finally, when you mention scrapping the feedback system? What, exactly, part/pieces are you referring to? Is it something I can just disconnect now or will that have to be when I get a new carb? I'm not 100% certain what the feedback system is.

Thanks a ton for your post, it was awesome!

 

Someone who knows carb engines better than me will have to answer this one. I don't *think* that there's a difference, and it seems like a really bad idea to attach an EGR pipe to a carb, but I don't want to say for sure and steer you in the wrong direction.

You have to change the carb, the distributor, and the control box that Roger mentioned all at the same time.

The feedback system is the stock carb, distributor, control box and computer (aka PCM, aka ECM) that your truck came with. It's named because there is a sensor on the carb that tells the computer how far the throttle is open - basically one of the first throttle position sensors put on a truck. It provides "feedback" to the computer via this sensor and with that information plus engine vacuum, it determines how far to advance the spark.

Advancing the spark means (I have a feeling you're going to ask) refers to an engine's capability of changing when the coil fires the spark plug. Contrary to popular belief, the plug doesn't fire when the piston is at the top of the compression stroke (if you don't know what the compression stroke is, go read howstuffworks.com's article on internal combustion engines). It fires it quite a bit before then (I know EFI trucks better than carb trucks, so that's what I'm going to talk about). On an EFI truck, the base timing is set at 10 degrees before top dead center (BTDC). This means that when the crank is 10 degrees shy of top dead center, the spark plug in the #1 piston is fired. This works fine at idle. Things change drastically when you are pulling a hill at 65 mph and your right foot is planted on the floor. The spark timing has to change to different driving conditions.

It used to be on very old cars that you had to manually adjust the spark timing. There was a lever on the steering column and you had to manually set it. As technology improved, we figured out ways to automatically adjust it. Cars in the 60's and 70's had mechanical advance distributors. The advance was controlled by springs and engine vacuum. Now, everything is done by computer.

The feedback system on your truck was Ford's very first attempt at computer controlled spark advance, and it while it was a good first try, it wasn't as reliable as the older mechanical systems. This is the system we are trying to get you to convert to. It's much better than what you have now. Of course, compared to a modern, all-electronic engine, it's very inefficient, but it's pretty darn good for 70's technology.

 

BTW I knew none of this when I started on this site back in 2002. I learned by reading and doing. I believe that you can't troubleshoot something unless you know how it works so I have always tried to read as much as I can about cars and that way, when something is wrong, I know where to start looking.

One of the problems is that with cars, there is an absolute ton of false information out there. Lots of people insist they know what they're talking about but likely wouldn't know which end of the screwdriver to use.

 

Thanks for that explanation. It cleared a lot up. Consequently, I just got done reading <a href="http://www.carbdford.com/viewtopic.php?t=5543">this</a> article on distributors, specifically timing and tuning the durashock 2. It went into great detail about initial, mechanical, total and vacuum timing. I think I have a pretty decent theoretical knowledge of those things at this point =P

So it sounds like I need a new carb, (probably intake manifold unless I stick with an older stock carb for now), and the durashock 2 ignition stuff. Cool. I think I can work with that =)