will get in the morning! Thank you.

 

An inline filter is fine. even if you had the filter that screws into the carb an inline is a good idea because the stock one plugs so easy.

 

If the idle mix screw are way out you have a vacuum leak and a lean condition . The carb is trying to keep up with the air flow. If the EGR is rotten in side you wont be able to tell with out taking it off doing a close inspection.

 

Yes, its running very rich but if i try to turn the idle mixture screws in at all it starts to run rougher.
There is no egr valve and the carb base plate has been swapped out with a new one that does not have a hole for the egr.
Its been a little over a year since I have done a compression test and checked the timing. I will also test the vacuum. Which hose is the best one to check? I was thinking the one that goes to the distributor.
I will also take a pic of the carb when it is warm.

 

A mechanic's vacuum gauge is a very valuable troubleshooting & tuning tool, for both the novice and expert alike because it will instantly show many different aspects at a glance, mainly, if the engine is at a good overall internal mechanical condition (cylinder compression, valve condition, valve timing) and, if it is also generally tuned and timed properly. Will also indicate exhaust restrictions, and test fuel pump output pressure. Pretty handy dingus for ten bucks.

It might take a little while to figure out just exactly what it is indicating, the finer points take experience but there won't be any question whether there is a defect in the engine or tuning.

Gauge has to be connected to a source of constant idle manifold vacuum. Either somewhere on the manifold itself or, a connection that is below the carburetor throttle plates. Most factory carburetors don't have this connection port included, because factory distributors are generally setup for 0 vacuum at idle RPM. Look for an unused connection on the manifold with a NPT square fitting, or if there is a vacuum brake booster connection at the base of the carburetor that can also be used to connect a vacuum gauge for test purposes.

 

Rich condition doesn't indicate a vacuum leak, but see what happens when you cover the air horn with a rag while it's idling.

If it ran well before don't waste your time on a compression check. compression doesn't go bad overnight.

Loosen your distributor up enough you can move it and see what happens. also check your firing order if there's any chance the plug wires were messed with.

 

Can't find my vacuum tester at the moment, I will have to look some more. I did replace all the vacuum lines and the carb base plate gasket previously.
The scoop is, I drove it today on the highway and some back roads for over half an hour. It ran just fine all around. The idle stayed the same, no roughness at all.
The difference here being that normally I drive it in town, its a big town. It takes an hour to get from one side to the other but even after driving it for a half hour it would run rough.
The other difference is that it was a brisk 45° here today. Normally it has been 60° - 70°
I am thinking that it is overheating and causing it to run rough. I dont know since the gauge doesn't work.
The other thing is that the choke butterfly stays mostly closed and if I try to open it at idle it almost dies. This would seem like a vacuum leak but like I said before everything has been replaced and the starting fluid turned up nothing.

 

Try choking it with a rag. if it speeds up you have a leak.

It would take serious overheating to effect how it runs very much. a little warm won't effect anything.

if it won't run without the choke on you have a problem you have to fix. probably in the carb.

 

Dial indicator can tell you condition of lifters and cam

 

Even at fully warmed up, the choke butterfly is barely open. If I close it any, or put a rag over it, it will die. If I open it up any it will almost die. If the carb is the problem, what internally would cause this? What should I look for when I take it apart? Or should I just get a new carb? Should I stick with the 2 barrel or get a 4 barrel that is about the same size?
My reasoning for thinking that it is overheating that is causing it is that, I had another 78 F150 that did overheat for sure and it would always make it run rough kinda like now. Plus driving it in the country it was fine but driving it in town makes it run bad.
What is a good method to flush the radiator? Im not sure that Im getting all the gunk out but also dont want to use anything too harsh.
I have heard that these modifieds are notorious for running too hot. I put in a cooler thermostat on recommendations but it didnt seem to help much. It calls for a 190, I put in a 180. Also, would an aluminum intake help? I want to get rid of some of that weight anyway.

 

Found the vacuum gauge. It was steady at 20 from the front of the intake at idle.
I am wondering if these vacuum lines are routed correctly. Does anyone know where I can get a diagram?
This picture is at operating temperature and the butterfly is still mostly closed. If i open it all the way, it will die.
I am loosing some vacuum at the crank case vent from the big hose at the back of the carb and one from the intake to the air cleaner. Are these really necessary?

 

OK a steady 20" on the gauge indicates (among other things) that it should idle crisp and smooth. This simple test covers a lot of ground for anyone following along out here in the cheap seats.

The ignition timing must therefore be reasonably close to factory spec, or it would never pull 20" vacuum. So, you're good there. You did mention in the OP the "carb was rebuilt about a year ago".

Was that something you know to be a fact (as in you did this personally) or, is this something that maybe the previous owner of the truck claimed right before the sale, or?? See where I'm goin' with that?

Somebody mentioned checking for worn throttle shaft. This is one of the very few DIYer show stoppers with these particular carburetors. It might be worth trying another known, good carburetor, but I would resist buying another carburetor, at least for now. One reason being simply because it's better to learn how to service and setup a carburetor and learn how they work.

Buy a good rebuild kit from Mike's Carburetor or somebody like that. Use your vacuum gauge to measure fuel pump pressure output. Takes about 5 seconds and then you know for sure. Make sure the output volume of the pump is in spec too.

Download the Autolite carburetor manual and study it, and disassemble, clean and inspect the carburetor carefully. Could also have missing parts like checkballs or the wrong parts, defective parts, etc, all kinds of stuff.

Carb cleaner sold in gallon buckets used to be powerful stuff, and it would make them gleam, but it has been banned. All those tiny orifices and air bleeds and such inside the body of the carb have to be free and clear or it will never run right. If the carb is full of corrosion and crap, the alloy pitted and porous, throw it away because it probably can't be cleaned. Pay particular attention to the float, needle & seat, float height spec and "wet" float height spec, meaning check the fuel height in the fuel bowl after it's actually installed on the motor.

Maybe the carb is toast by now, but I doubt it. Have to inspect it carefully to be sure anyhoo. If it's in good shape set it up and adjust everything by the book. This is impossible without the shop manual, at least for a novice. There ain't no other way! Ask me how I know.

Once a carburetor is setup correctly, they should last a long time without any attention. Maybe the idle mixture can be tweaked between winter and summer along with the accelerator pump shot. The proof of a good sharp factory engine tune will always be good easy starts, smooth power and very clean burning spark plugs.

Also focus on Ignition itself, a lot of "carb problems" are really defective Ignition. It needs to be a good fat HOT spark at all times, especially under load and at speed.