The Stovebolt Site Forums The Shop Area Engine Shop heat riser valve

here i go again, seeking the knowledge of you stovebolters once again. I've read up on many of the forums pertaining to the mechanical heat riser valve and how it functions. I do understand how it works with the spring and it's purpose. However here's what i've come across. My 235 heat riser valve was seize solid in the open position when i purchased the truck, furthermore the slotted end of the rod was broken off. Since i had a couple of spare exhaust manifolds with working free heat riser valve from the same year (1950) I replace the one on my truck a few weeks ago. Today i went to put the spring on and quickly realize that the counterweight (half circle) is located in a different position when the damper is in the closed position. The flat bottom section of the counterweight is facing parallel to the ground when the heat riser valve is closed (engine cold position) when open (engine hot position) the counterweight (half circle) is facing the engine block (flat side facing driver side fender). Is this correct?

Here is a picture of how the spring should be.
This picture shows the weight in the cold/closed position.

thanks, the flat section of the counter weight is facing down when cold and the spring has 1/2 turn tension on it. When the engine warms up, the spring tension decreases allowing the counterweight to move freely. The problem is at idling position even with engine hot the flat section of the counterweight is facing down, it does however move vertically when i rev the engine but returns to horizontal position at idle even when hot and with no tension on spring is this normal?????

DJ,

I found that the heat riser valve on my '36 Chevy was constantly sticking. Others I spoke with had the same problem. So about 30 years ago I made a shaft and bushings pressed into the exhaust manifold out of stainless steel and that solved the sticking problem permanently. It's still working properly. That may be worth considering while the manifold is easily accessible.

Once the engine speed rises above idle, the exhaust volume and extra heat will make the bimetal spring lose more tension and the flap valve will go to the full-open position. If you're a brave soul, try propping the hood partway open and riding the fender to watch the valve while a friend takes a drive around the block!
LOL!
Jerry

Its the 21st century Jerry. They have this gizmo called a Go Pro now for such things. They also have a thing called Google where you can look up stuff like Go Pro.
Your pal

Hey, I like the visual image of some doofus with his feet on the front bumper and his head stuck under the hood, watching that counterweight! I'd even be willing to bet the diploma hanging on his office wall has the word "engineer" somewhere on it!

Jerry

thanks i think i'll use a heat gun instead