I am now the proud owner of a 1982 (sep-81) F-100 Longbed, automatic, 5.0 with only 85,000 original miles! Its a classic! The original jack and tire iron have never even been used. still has the factory spare tire, never used either.

I have one problem with it tho. It seems to start fine, but after it gets warmed up, it likes to stall out, and I have to give it more gas. This is my first carb, so I'm not sure about everything there, but I did take out the 'heat riser' as the bottom nor the top was actually connected to anything, and the bottom heat shield is very loose. What is the purpose of the heat riser, and would it cause this sort of problem?

 

The heat riser on the air cleaner helps keep the intake air temperature to the carb warm.


On a cold morning, when you first start the truck, a little flapper in the air cleaner snorkle diverts warm air to the carb to help the engine warm up faster. When the engine heats up the flapper opens up and alows cooler air to enter the carb.


On a really COLD day, this flapper will never open up, or will only open a partial way open, so it can blend the heat with the cool air to keep the intake air at a suitible warm tempurature. This helps to keep the Carb from icing up in cold weather.

Make sure the flapper is not rusted shut and moves freely. Too hot of air can cause a vapor lock to occur.


There is also heat riser system of tubes on the carb connected to the choke, on some models.


Also make sure your choke is opened up all the way when the truck is warm. This can cause a rich condition and poor drivability.

 

what is a good replacement material for the heat riser tube? could I use a big hydraulic hose, or a radiator hose? what is on there seems like 2.5"
dryer vent tubing. but it is too small and won't stay on. I was thinking about bendable steel exhaust tubing for a replacement heat riser. How can I secure the bottom shield portion of the heat riser, in between the engine and exhaust downtubes?

what is the best brand of repair manual for one of the newest f-100s on the planet?

 

They sell the heat riser tubes at most auto part stores. They are universal, but are made like the original ones. They come in different sizes and cost around $5 to $7 dollars. Just get one to fit. If it's loose you can use regular hose clamps to hold them on.

It should be bolted onto the engine with two nuts and bolts, or threaded studs. Tighten these up may make it tighter. If the riser shield is cracked or damaged, you can take it off and weld it, or get another one from a wrecker.

If you can find one of the older Haynes manuals they are the best. Having both a chilton and Haynes around is a good asset.

When you can though I recommend looking up and finding the original Ford manuals to your truck. They are very comprehensive.

Hope this helps.

 

if the heat riser is off and it dont start stalling out till it is warm, that wont be ur problem if the truck is warm it wont be pulling air off the exhaust to help it warm up

 

02 stang, what could be my problem then? I am gonna get the heat risier, but wondered if that would be the culprit. If it is not stalling out until I get it warmed up, what should I look for?

 

I would start by looking at the choke to see if it's fully opened when warm. I would also check your air filter to see if it needs to be changed. That would be the very first things I'd check. A malfunctioning choke and/or a clogged air filter can cause a rich condition and flooding, especially with a warm engine.


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Since you disconnected the Heat riser I doubt this is the cause of your problem, unless it's cold outside where you live.


The only way that the heat riser could cause those problems with the engine warm is...

A: If you were getting heat when you were not supposed to when the truck is warm, and the ambient air temperature entering the carb and intake is too hot. The "flapper" in the air cleaner snorkle is rusted in the closed position as example. This can cause a vapor locking condition. Sputters, engine miss and cough, engine dying etc... Not likely with it disconnected from the heat source.

B: If you were not getting any heat at all on a really cold freezing day. The flapper in the air cleaner snorkle could be rusted open. This can cause Carb Icing and freezing. The air entering the carb and intake being so cold that it freezes the carb up, and blocks fuel flow. Causing Sputters, engine miss and cough, engine dying etc. This could be likely with the system not working properly. However the ambient air will have to be below 65 degrees or there abouts, give or take.

If this is the cause, when your truck starts acting up, park and check the surface of the carb imediately. Check to see if there is frost, or if there is dew on the surface of the carb from the frost "melting".

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There is a thermostatic bi metal sensor in the air cleaner that is hooked to manifold vacuum, if the air entering the air cleaner is too cold, it sends vacuum to a vacuum motor located on the air cleaner snorkle. This controls the heat riser air blend door (flapper) in the snorkle and alows heated air from the exaust manifold to enter the air cleaner.

As the air temp rises in the air cleaner due to engine heat, the bi metal sensor "senses" the change in temp, and begins to shut off vacuum to the "flapper" This is where it "blends" the heated air from the exaust manifold, with the cold air from the air cleaner's normal air intake. It will continue to blend the air to keep it at a constant controled tempurature inside the air cleaner until...

A: The air in the air cleaner is warm enough not to need the extra heat and the bi metalic sensor, opens the flapper up all the way.

or

B: The air entering the air cleaner still remains too cold without the heat risers help, and it keeps blending the air to keep it at a constant warmer temp, or it gets too cold and the flapper closes and full heat is applied.


This process is controlled in all engine conditions, warm, or cold, and does not depend on if the truck has just been started or if it's been running steady for a week. It soley depends on the tempurature of the air entering the air cleaner and the carb at the moment.

Hope this helps.