Heat riser "butterfly" valve

keithfullmeryahoocom

I'm wondering how important the function of this is.   I've had it all apart (after many, many, moon of soaking in kerosene) and finally got it free and moving easily, and at least mechanically functional.   After sitting  it on my wood stove, which I believe should duplicate the necessary temperatures,  It doesn't seem to want to open and close automatically at all.   Probably the thermostatic spring or maybe the combination of the attaching springs.  I attach pictures of the top and bottom of way it was, and is assembled.  I'm wondering if the assembly is incorrect.  

Did these things ever function very well?   And although I understand the theory of  the benefit, was this action of the butterfly valve worth maintaining?  If not, where would you set it for every day, all season driving?

I've seen a lot of literature regarding the locking up of these, and I guess I'm just wondering if keeping it moving is imperative to the operation.

Thanks, Keith

Geoff

The operation of the spring loaded type of heat valve is by the passage of exhaust gases.   when the spring is cold it has more tension, therefore the exhaust gases will be deflected through the "hot box".   As the temperature increases the tension decreases, so the  gasses going past will cause the  valve to open more easily, and less heat around the hot box.   So you won't actually see the valve open as you heat the manifold up statically.   Depending on where you live, and if you use the car in winter or not, it is over to you really, but with the more volatile fuels these days it is most likely advisable to  wire the valve  open.  This reduces back pressure, and   keeps the heat away from the carburetor.   I would advise making up a new heat deflector also to give a greater area of shielding from the hot manifold to help avoid the problem of vapor-lock.   Good luck, and Happy New Year.

Geoff 

keithfullmeryahoocom

Thanks, Geoff.

Anybody have a good, detailed picture of how a heat deflector looks and how it is attached?

DavidC

I believe the heat deflector Geoff is referring to is the one installed halfway among the carb spacers/gaskets. It can be fairly thin tin or even better SS. It is held in place by the carb mounting studs. It shields heat from the carb bowl in a similar manner to the way other heat shields block muffler or catalytic converter heat from the tranny. Just take a look at Hudson motor pics and you'll see them. They are available for sale by HET members including Paul Schuster, but I believe Geoff is suggesting you make a custom over-sized shield.

befishers1

The pictures you show look like you have it correct.  You said it freely moves, did you try it once fully assembled?  I had one that was corroded and I replace the flapper, it was about 0.010" longer than the original and would work well until the final 1/10 of a turn of the two bolts and that would clamp it solid, I added a second gasket and it works freely again.  The other issue is the spring used to open it is shown in your picture as stretched and one end may have broken off.  The top spring is a torsion spring and has more air around it and holds up better.  The extension spring used to open it on the underside can get hot enough to lose its tension.  When I reassembled mine I had to work on the tension of this spring on the bottom so that when the torsion spring on the top was hot and the engine was running the spring on the underside had enough tension to close the damper.

I live in Florida so I keep mine fully open most of the time by simply popping the torsion spring off the top but I keep it moving enough not to seize up again.

Geoff

Here's a pic of my Jet motor with the extended heat shield to protect the carby.

Geoff