B2B Heat Riser Question

[monkeyhuey]

I have a 1950 Dodge B2B and my thermostatic spring is broken.  My question is this:  with the spring non-functional, is the default position of the ‘flap’ open or closed?  More accurately, when the spring is non-functional, are the exhaust gases being directed up into the carburetor or not?  I could only find one small diagram of the operation of this flap in an old service manual, but it was a little confusing as to the position of the flap when the spring wasn’t operating.

 

With no spring, the counterweight falls to the right, or clockwise when looking at the engine from the side.  The range of motion is backward and upward or counterclockwise.  An article on this site describes the operation of the thermostatic spring as if it relaxes when it gets warm, therefore I am feeling that with no spring present, the default position of the flap would be in the ‘warm’ position, or open – meaning exhaust gases flow out the exhaust pipe and Not into the carburetor.  Can anyone confirm this?  Or clarify the operation?

[TodFitch]

Looking at the manifold from the passenger side, the heat riser is in the hot position when it is clockwise as far as it goes.

 

Basically the spring holds the riser in the cold position. As it gets warm it weakens and the counterweight pulls it to the hot position. And, being a spring, if there is lots of exhaust gas flow, the spring will give way to that too allowing the riser to move to the hot position. You can see that on a cold engine by goosing the throttle and watching the counterweight move toward the hot position.

[Desotodav]

I saw these on Ebay a while back and reckon that they could be easily modified to do the trick... http://www.ebay.com.au/itm/190745341276?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

[P15-D24]

And springs are available in the U.S. 

[monkeyhuey]

Thanks...  I probably won't be driving the truck in cold weather, so for now I'll just leave it as is.  I was actually thinking of using another Choke cable and create a manual heat riser from in the cab...  I also found an old spring for  Buick on ebay - called the place and they have many different sizes of springs that could be modified if need be.

[monkeyhuey]

here's mine, btw....  rescued from 30+ years of barn storage!

 

[ggdad1951]

solid looking truck!

[Merle Coggins]

Nice lookin' truck and interesting pin stripping. I wonder why they didn't carry it through on the cowl section between the hood and door?

 

Merle

[monkeyhuey]

the truck was originally dark green (like so many were!).  my guess is they did the pinstriping with the panels off the truck and never thought about the cowling until later...

 

don't know too much about the history, but I suspect the reason it was parked sooo many years ago is that the master cylinder was locked up.  there was one loose bolt of the three when I got under there.  It appears as though someone had taken it off to try and rebuild it but couldn't get the 'guts' out...  so they attempted to remove the stop plug but badly damaged it.  They couldn't get it apart to rebuild it so they just stuck it back on the truck and parked it... my guess.    I had to cut it off flat, drill it out and re-tap it...  luckily, the old threads came right out and the original threads were salvaged...  making new brake lines next...