56 Buick

56 choke thermostat tube issue

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in section 3A, page 3-5 there is a description of the right side exhaust manifold.  It says, in part,  the carburetor choke heat stove consists of an  alloy steel heating tube mounted in a drilled hole in the manifold and a heating chamber "located on the outside of the manifold".  So it would appear that the hole in the center of the manifold (on the engine side) is an opening into the heating chamber.   

section -3-16 sub section a: describes the choke system for the Carter 2 bbl.  It says, in part,  that there are two slots in the choke piston cylinder that allow vacuum to draw heated air up from the choke heat stove, and around the thermostatic spring, past the piston , and into the intake manifold. 

In section 3-20 sub section g: the manual says that except for some minor details of construction, the choke on the Carter 4 bbl is identical to the choke on the Carter 2 bbl.

For the Stromberg carb, in section 3/23, subsection h: it says there is no vacuum employed in that carb's choke system. The choke is controlled manually. 

Then in section 3-28 sections a and 😄 it talks of the Rochester 4 bbl choke using vacuum for the piston and "restrictions"  'in the choke housing  are the source of the vacuum to draw air through the choke heat stove. 

 

What is not in the book ( that I can find) is talk of the plug in the end of the alloy metal heat tube.  But on my spare manifold it looks for certain that this was a factory plug.  Maybe a stainless steel ball.  I will try to get some good pictures of that tomorrow but I wonder if that ball is there to slow the air flow in the heat tube in the choke stove system.  Perhaps to prevent the choke from opening fully too soon?  At any rate, the one I can look at does not appear to be merely a plug from a rotted tube.  

 

@56 Buick If you hooked your choke heat riser to that hole in the center of the manifold, then I think that is incorrect. But it may work okay.  I can't imagine either port would result in a hotter air temp in the choke stove system.   However, on my car, the heat riser pipe runs from the choke housing down to the manifold, then turns to run parallel with the inside edge of the valve cover to the rear of the engine.  Then loops around the back of the head and comes forward to connect to the alloy metal heat tube at the rear of the exhaust manifold. 

 

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25 minutes ago, JohnD1956 said:

in section 3A, page 3-5 there is a description of the right side exhaust manifold.  It says, in part,  the carburetor choke heat stove consists of an  alloy steel heating tube mounted in a drilled hole in the manifold and a heating chamber "located on the outside of the manifold".  So it would appear that the hole in the center of the manifold (on the engine side) is an opening into the heating chamber.   

section -3-16 sub section a: describes the choke system for the Carter 2 bbl.  It says, in part,  that there are two slots in the choke piston cylinder that allow vacuum to draw heated air up from the choke heat stove, and around the thermostatic spring, past the piston , and into the intake manifold. 

In section 3-20 sub section g: the manual says that except for some minor details of construction, the choke on the Carter 4 bbl is identical to the choke on the Carter 2 bbl.

For the Stromberg carb, in section 3/23, subsection h: it says there is no vacuum employed in that carb's choke system. The choke is controlled manually. 

Then in section 3-28 sections a and 😄 it talks of the Rochester 4 bbl choke using vacuum for the piston and "restrictions"  'in the choke housing  are the source of the vacuum to draw air through the choke heat stove. 

 

What is not in the book ( that I can find) is talk of the plug in the end of the alloy metal heat tube.  But on my spare manifold it looks for certain that this was a factory plug.  Maybe a stainless steel ball.  I will try to get some good pictures of that tomorrow but I wonder if that ball is there to slow the air flow in the heat tube in the choke stove system.  Perhaps to prevent the choke from opening fully too soon?  At any rate, the one I can look at does not appear to be merely a plug from a rotted tube.  

 

@56 Buick If you hooked your choke heat riser to that hole in the center of the manifold, then I think that is incorrect. But it may work okay.  I can't imagine either port would result in a hotter air temp in the choke stove system.   However, on my car, the heat riser pipe runs from the choke housing down to the manifold, then turns to run parallel with the inside edge of the valve cover to the rear of the engine.  Then loops around the back of the head and comes forward to connect to the alloy metal heat tube at the rear of the exhaust manifold. 

 

My car definitely does not have any restriction or ball sitting in the end of the alloy tube. I know that if I blow compressed air into the alloy tube then it comes out of what now appears to be the heat chamber. Which is where I have the stove pipe inserted. 

 

In comparison to your setup, I guess that with my setup it is possible the stove pipe could be hotter (at the choke thermostat) given it has less distance to travel to the choke thermostat.

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Sounds like the issue is whether the alloy tube end (where the choke stove pipe is usually attached) should be blocked. So that the stove pipe is not necesaarily drawing heated air but rather just heat?

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Posted (edited)
13 hours ago, 56 Buick said:

Sounds like the issue is whether the alloy tube end (where the choke stove pipe is usually attached) should be blocked. So that the stove pipe is not necesaarily drawing heated air but rather just heat?

 

Does  draw heated   air as the end does not access the inside of the exhaust manifold from my understanding.  The air inside the enclosed tube gets hot as well as the tube itself.  It takes time for the heating to occur so the engine will stay at high idle thus warming faster.  If direct flaming hot exhaust were to travel that tube the choke coil would unload the fast idle cam  much to quickly.   

Edited by avgwarhawk (see edit history)
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Posted (edited)

Picture posted my Mr. Earl of a 56 manifold.  Air is drawn in at this end and runs through the tube inside the manifold that exits the other side. When this occurs the air is heated.  

 

P1010835.thumb.JPG.f34c0d3166a1139b96a1f

Edited by avgwarhawk (see edit history)

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From avgwarhawk's reference above.  This is from 1954 manual but concept is the same.

 

769507391_Screenshot_20200107-115339_SamsungInternet.thumb.jpg.92d83f9b13044a3efd2bdbf89f711f84.jpg

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On 1/5/2020 at 4:19 PM, lancemb said:

To clarify, here is a pic showing the tube path on a 57 manifold.  The 56 manifold uses the exact same tube, through at least 59 (and I think 60).  The pencil shows the path of the tube and you can see it sticking out on the bottom.  The other pic is of the tube itself when not installed (an NOS example).

20200105_141153.thumb.jpg.026f0da307bf1491400f98047a03d5c2.jpg

 

20200104_213317.thumb.jpg.b79dbfb22608f8d2a1ab125963ab54cd.jpg

 

 

Best description here.  The long pipe in the second picture. runs directly through the manifold at the angle shows with the red pencil pictured.  Hot exhaust flows around this tube heating the air the fresh cool air that is being drawn in from one end, out the other and up the tube to the choke housing. 

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15 hours ago, 56 Buick said:

Sounds like the issue is whether the alloy tube end (where the choke stove pipe is usually attached) should be blocked. So that the stove pipe is not necesaarily drawing heated air but rather just heat?

 

Not to belabor this, but just to clarify:   I am not saying there is, or should be,  a restriction at the end where the upper tube attaches to the exhaust manifold, which appears to be this end:

DSC00309.JPG.7b8ca80e38d277a274efaf81e6460602.JPG

 

Instead, the opposite end of this lower tube as shown here:  DSC00307.JPG.519d4ec89a129de4879328daf76e50f1.JPG

 

This end of the tube is capped off.  I scraped it to make sure it was a plug and not just some debris.  At first I thought maybe this was a ball bearing intended to block part of the opening to cause a restriction.  I now see it is a solid end and it appears impossible that air could be drawn into the lower tube at this location.   

 

A probe in the hole in the center of the manifold ( the hole just below the letter M in the word Workmate) showed that this is a chamber of sorts, not just a piece of tubing itself:

 

DSC00308.JPG.fbad5648a33c4e4a863247186d92bad9.JPG

 

And one can see the subject tube inside the manifold running from the last port to the area where the plug is.  

 

So my original comment was, if this lower tube is plugged, and it seems to be plugged from the factory, then how does the vacuum draw air into the lower tube?  That's why I thought the tube Lance showed may have had perforations under the label.  That labeled area appears to fall inside the chamber behind the center hole. And that would be consistent with the description in the manual saying that the choke stove chamber is outside the exhaust port area.  And if 56 Buick blew compressed air into the exposed part of the lower tube and the air exited from the center hole than obviously there has to be a perforation in the lower tube to allow that (or he just blew a hole in it by trying).  

 

At any rate, I would definitely agree that one does not want exhaust gases inside the choke housing.  

DSC00303.JPG

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Posted (edited)

All indications and as I read it from the manual and pictures, the tube should not have a blockage.   Let others confirm as well. 

Edited by avgwarhawk (see edit history)

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16 hours ago, JohnD1956 said:

Not to belabor this, but just to clarify:   I am not saying there is, or should be,  a restriction at the end where the upper tube attaches to the exhaust manifold, which appears to be this end:

DSC00309.JPG.7b8ca80e38d277a274efaf81e6460602.JPG

Okay, this is the same as mine where this end of the tube is clear and outside air can be drawn into the alloy tube .

 

16 hours ago, JohnD1956 said:

Instead, the opposite end of this lower tube as shown here:  DSC00307.JPG.519d4ec89a129de4879328daf76e50f1.JPG

 

This end of the tube is capped off.  I scraped it to make sure it was a plug and not just some debris.  At first I thought maybe this was a ball bearing intended to block part of the opening to cause a restriction.  I now see it is a solid end and it appears impossible that air could be drawn into the lower tube at this location.

This is the same as my manifold where this hole is blind with no effective opening.

 

16 hours ago, JohnD1956 said:

A probe in the hole in the center of the manifold ( the hole just below the letter M in the word Workmate) showed that this is a chamber of sorts, not just a piece of tubing itself:

 

DSC00308.JPG.fbad5648a33c4e4a863247186d92bad9.JPG

 

And this 'opening' '(the hole just below the letter M in the word Workmate)' is where compressed air vents from when I blow compressed air into the alloy tube at the other end of the manifold.  This 'opening' is where I have inserted my choke stove tube with the other end attaching to the choke thermostat housing cover.  So the system operates by the choke thermostat housing having a slight vacuum that will draw air up the choke stove tube.  Outside or external air is drawn in the other end of the alloy tube with that air being heated by the heat of the exhaust passing over/around the alloy tube.  The heated air (not exhaust gas) then enters the choke stove pipe.  The heated air travels up the choke stove pipe to the choke thermostat housing where the heat causes the bi-metal coil spring to move the choke plate.

 

Thanks all.

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