Alright, today I am going to adjust the idle screws on my carburetor. I haven't done this before, and am wondering if it is as simple as it sounds or am I going to blow the truck up. I have a 1979 F-250, I'm not sure what the engine is, I think a 460. It is a trailer special.

I bought it a week ago or so and it had always idled roughly, especially after warming up. Yesterday it finally died at a stoplight for the first time. I can't have that happening here in the big city.

Any advice?

 

got a vacuum gauge handy?
It'd also be nice to find out what rpm you're running at idle.

 

No vacuum gauge handy nor tachometer, nope, so I don't know the RPM. Can't buy one as I am broke, unless they are super cheap.

 

well vacuum gauge at autozone should be $5-$10. A fine investment.
I'd get one, keep it in the tool box.... you could at least rule out a few things.

 

What carb? the easiest way to set the idle mix is this.

Set curb idle to desired RPM (550 on that 460 says the tag.. but most likely it won't idle that low if your having problems..) so justt high enough for a smooth idle.

Then adjust one idle screw in until it stumbles and just wants to run, then slowly back it out until it reaches its highest rpm, then in a quarter turn.

Move on to the other mix screw and repeat.

Readjust your curb idle once more.

And repeat the air mix process again.

Then readjust curb idle. Done.

It helps if you have a tach, you can just set each one until the rpm's settle, but I just do it by ear. If the RPM's just keep rising and the air mix screws are all the way out, then you have a piece of junk somewhere, and you need to clean the carb. Some like to use a vacuum gauge whilst doing this but you don't need one.

Just keep in mind that it helps to have everything else in good order (clean plugs, proper gap, clean cap and rotor, good wires..) Also too small of an air cleaner will have an effect on air mix. I think 14x 3" filter is optimum (if memory serves..)

Also make sure that your choke plates are opening fully.

 

With the truck shut off, you can gently turn both mixture screws all the way in, then back them both out 1.5 turns. Then with the truck running you can adjust them for smoothest idle. But the best way is to use a vacuum gauge. It's one of the best diagnostic tools you can own. No offense, but if you can't invest in a $10-25 tool for your truck, then an old truck that's already having issues is going to be very problematic for you.

 

OH... it helps to know what motor you have.. this should be one of the most important things you should know about your truck, pick up a repair manual (I have one for every vehicle I ever owned (some 24 in total..) I keep them even when I get rid of the car/truck) keep it in the can so everyday when your sitting there doing nothing but staring at your feet!! you can have something interesting to read...

Second thing.... I just went through this with my brother in law.. whenever you get a new vehicle, always do a tune up, (new fuel filter, plugs, wires, cap, rotor, condensor..) keep an extra ignition module in the glove box along with a test light..) go to sears and get a good one. No matter who you bought it off of, or what they say, you can't trust that all the maintenance was done. Its cheap insurance, and at the very least you know that you did it... and your ownership is starting off with a clean (ish) bill of health.

Along with an oil change, and trans service...

 

Never had an issue adjusting carbs

 

A few of the most important tools you will buy, and NEED with an older truck is a vacuum guage, timing light, tach/dwell meter (if you have points), multi-tester, and a test light. I would suggest if cash is tight, go to Harbor Freight. On a budget they will be your friend, and you will get these necessary tools you will use time and time again.

Go get what is most needed for your truck, and go from there. One word of wisdom I found if you see something there, and needed it, grab it because next time you come back they will all be gone, and if you ask the help there they will look at you like you got three eyes.

One more thing, go to flEbay and buy the shop manuals on CD for your particular year truck. It will run you about $30, but is packed with valuable information. You can read up on what your working on, do searches, and print out certain pages you need. If they get dirty, just toss em out, and print them again the next time.

If you have those tools in your tool box, do a search on this site, ask a few questions, there is nothing on your truck you can't fix, provided you got hand tools. If not, till you get to this point you will know the drill!! (Back to Harbbor freight again)

Good luck with your truck, and if you can, throw a few pictures up, we love to see truck ****!!

 

I went to the library and got the 73-79 ford truck and bronco manual and I've been looking that over. Let me just say that, even as a total novice mechanic, or worse, I feel that the Haynes is too vague or broad in scope. All I want is the info for my exact model of car. Thanks for the advice. I will get some of these things taken care of when funds become available...

I can spring for a $10 tool, no problem. Just can't do a $35 tool right now.

If I had to choose, would I buy a tachometer or the vacuum gauge first?

 

Test light, multimeter. You can tune without a tach or vacuum gauge right now.. but if you run into another issue (electrical, which you will..) you'd be glad the money was spent on an electrical diagnostic tool instead. Multimeters can be had for cheap.

 

Okay so I took a looksee and I have some pics to share, but I do not know how to share images on this forum.

Of course now, today, it is running pretty well and won't die. But anyway, according to my Haynes I have a 2150 2 barrel carb, or at least that is what it looks like to me. Now, I want to adjust the curb idle, yet the screw is strange. It is a small hexagonal type thing. Am I supposed to use a pliers on this thing?

 

http://1.bp.blogspot.com/_hYHo963Qbe...h/DSCN6689.JPG

 

http://1.bp.blogspot.com/_hYHo963Qbe...h/DSCN6684.JPG

 

Hey! Nice looking dent you got there!! That is nice you can get your hands on those manuals at the library! You can get a multi tester on sale at Harbor freight for 3-4$, vacuum guage $10, timing light $25, test light 2-3$. Just keep an eye on them they have sales every week. I got a few great deals on socket sets, that are as good as any socket you will ever need.

As said before, you can tune with out some of these tools, but it will give you a better piece of mind knowing it is done right, and you did it yourself!