Choke type?

[txtj79]

I have a 350 with a Q-jet 4bbl on a 1980 C-10 and a 1978 C-10 with a 305 and a Q-jet 4 bbl on it.  Both trucks have identical choke set ups.  Can anyone explain to me how the choke works?  It looks like a electric, but there is no electrical connections.  It's not a manual, but it doesn't have a coil on the intake like the older models.  It has a round black cover on it with markings for lean and rich that looks exactly like an electric but with out a connection.  What is this type of choke called?  I can't figure out where the coil gets its heat from.

Thanks,

T.J.

[TexasRed]

Perhaps manifold heat?

[Dragon]

It's a Thermal Choke, the Coil is under the Black Cap, much like your Standard Electric Choke.....  Basically the Way it works, is there is a Vapor Tube that is mounted on the manifold, and routed up to the back of the Choke Assembly, ending with a Fitting that blows air into it to heat the Coil....

It's Pretty much the same Idea as the Manifold Mounted Choke/Divorced Choke Assembly, but it is actually more efficient in heating the coil up faster... 

Most will buy an Electric Conversion from a Local Parts Source, and Convert it over to the Faster,More Efficient setup(Unless like me you like a Bit of Nostalgia, and your Willing to replace the old parts, with newer pieces, then just deal with a slight delay in getting up to proper Operating Temps)....

[txtj79]

What size would that tube be?  I have one about 1.25 inches in diameter that runs up from the side of the exhaust manifold up to the bottom of the air cleaner.  Is that it?

So, if my other truck doesn't have a tube like this, then the choke isn't really working is it?

Thanks for your help.

T.J.

[Dragon]

What size would that tube be?  I have one about 1.25 inches in diameter that runs up from the side of the exhaust manifold up to the bottom of the air cleaner.  Is that it?

So, if my other truck doesn't have a tube like this, then the choke isn't really working is it?

Thanks for your help.

T.J.

A pic of your Setup currently would help out tremendously.....  Really you should be able to notice weither or not their is a threaded fitting connected to the Choke Assembly, and going down to the manifold....

Sometimes people will disconnect the Carb Choke Assemb, and bypass it will either a manual hand activated setup, external electric Choke, or etc....

[leveldowen]

What size would that tube be?  I have one about 1.25 inches in diameter that runs up from the side of the exhaust manifold up to the bottom of the air cleaner.  Is that it?

So, if my other truck doesn't have a tube like this, then the choke isn't really working is it?

Thanks for your help.

T.J.

That bigger tube running up from the exhaust manifold is a hot air pickup for the thermac air cleaner set up.  A thermally controlled vacuum switch opens and closes a valve in your air cleaner housing routing in hot air to keep the inlet charge at a consistent temp in cold weather and during warm up so it runs smoother.  You can yank that tube and plug the vacuum line that controls the flapper valve in your air cleaner to disable this to bring down inlet temps if you can deal with some slightly rough running while cold.