hey everyone, i own a 80 f100 I-6 300, it was my grandpas and he died 4 years after he bought it new, anyway the truck has 77,000 miles and im having problems with low idle it tries to die when the motor is cold have no idea how to adjust the carb on it and would like to know what engine oil is best for these creatures i was todl i can use 15 40 but i been using 10 30 in it. Thanks for your help.

 

10W-30 is fine. where you live it will work year round.

The low idle problom is most likely a choke related problom. If you have no skills related to tuning carbs I would recomend taking it to a shop that has a guy over 55 working there.

The carb is a carter YFA.

The choke should have a fast idle cam, possibly with a fast idle set screw. you can try turning that in a bit to raise your fast idle when your choke is on. The easiest way to verify choke operation is to remove the air cleaner and have someone start the truck while you watch. The choke should move freely to a partialy closed position and kick the idle cam over. The 80s trucks used either an electric choke or a hea triser choke. The electric models have a wire going to them. The heat riser style has a tube going from the exhaust manifold to the black choke assembly. The tube can become clogged with soot and render the choke useless.

The early 80s had alot of smog junk bolted on. You could have dashpots, idle motors, and other various emission compliance stuff that can be causing the problom as well.

Once again, If you have never realy messed with carbs and dont have the intention of learning how too I would take it to a shop.

 

If it's anything like my '81, you'll have both an electric choke and a heat riser tube.

The heat tube going from the manifold up to the choke does have a tendency to plug up (as Flipkos stated) and/or will sometimes rust off. If you're into mechanics at all, you can easily replace it by bending some new pipe and putting a fitting on the end.

As for the electric choke part, there's a large black plastic housing on the back of the carburetor. That's the choke thermostat housing and has a large spring inside of it. When the engine's cold, remove the air cleaner and look at the butterfly plate at the top of the carb. It should be just a slit (about 1/16") open. If not, loosen the three little screws that hold down the large thermostat housing and just rotate it by hand until the valve is just open a tiny bit.
If it's completely closed, you'll have a horrible time starting it, and if it's open too much, it'll have a difficult time staying running.

Once you have that set, tighten the three screws and start the engine (no need to put the air filter back on yet). It *should* start and stay running without a problem. Once it's running, look at the back of the carb for the idle screws. They are two screws that are just on the linkage and have springs on them. Look to see which one presses against the body of the carb itself and which one presses against some moving linkage. The one that presses against the body adjusts your normal idle while driving and the other adjusts the idle when your engine is cold. Since your engine is cold, screw the latter of the two in or out until your engine is idling at around 1500 RPMs.

Let the engine get to full operating temperature and look at the butterfly on the top of the carb again. It should be completely open, ie. straight up and down. If it isn't, loosen the 3 screws on the choke housing and rotate it slowly and gently just until it's fully open and no further. If you go further, it'll affect how much it closes when it cools back down, and you don't want that. Tighten the three screws back down.
Adjust the normal idle screw (the one that presses against the body of the carb) until your RPMs are at 700.

Your choke should be completely set and ready to go.



If you're going to be driving that truck for a while, it's best to learn how your carb works. Carb guys can charge quite a bit for even simple adjustments, and those carbs like to fall out of tune easier than they should. I got my Bronco with a 300 I6 about 4 years ago and I know absolutely nothing about engines and my two previous vehicles were fuel injected. It was a fun learning experience and has saved me TONS of money. I'd recommend it. People on this site will help.




As for the smog stuff, yours is a touch older than mine, and all mine had was a smog pump, EGR valve, and a catalytic converter. They didn't start cramming more on until around 82 or 83.

 

A local shop with a guy who knows his stuff around here would charge about $40 to tune a carb. The problom is is finding a guy that has actualy tuned a carb before. A lot of idiot kids think they can cause they sat an edelbrock on a 350 and made it run. I am 28, and know how to tune carbs. I learnd most of it from talking to guys over the age of 50. Those SOBs know their carbs.

 

Heh, exactly. I'm 29 and that's where I learned it all from too. It's definitely a fun (and rewarding) science, but it's best to learn it from someone who truly knows what they're doing.

 

Those old buggers know their stuff. You just have to put up with being told how to wipe your own arst three times an hour. If one is willing to listin they are great.

Best skill I ever learned is, Dont walk in and tell a guy whos been doing somthing for 30 years how it is done. You will loose 100% of the time.................Even if you are right.

 

thanks guys it runs great when it gets warm but since day one this truck has never ran a normal temp always close to the cold line and has never ran hot its a great truck wouldn trade it for nothin i jus need to learn more about it lol ill try what yall said and see what happens. Thanks

 

Always cold? I would change the thermostat.

 

The idiot gauges in these vehicles cannot be relied on. It may actually be heating just fine.

 

If you've never done it, I'd change the thermostat, just to be sure. Get a 195 or so. (Some'll recommend hotter.)
If not, it simply may just be the voltage regulator on the back of the gauge cluster and nothing more. Mine will say it's barely warm 20% of the time, perfect operating temperature 70% of the time, and way hot straight up and down 10% of the time, and the temp in the engine never changes. =P