What's the spring loaded assembly...

...on the right exhaust manifold on a late model Flathead? There is a 4 inch (or so) disc that is mounted to the right exhaust manifold. It has a flap that basically controls flow into the manifold from the left side since the location of the assembly is where the left side manifold connects. The left side manifold dumps into a tube that crosses under the engine and connects to this part of the right side manifold, then the whole thing dumps out the back.



I didn't bother cleaning it up, but since I may be using the factory manifolds for some time, I may as well get this thing fixed. The flap does turn with some effort, but it doesn't flip back. I think I can get it apart and cleaned up. I just wonder WTH it is. What purpose did it serve?

I googled it, but without knowing what it is called, I didn't find anything I need.

 

turbo waste gate on the real late ones



..or it could be a heat riser, which promotes intake manifold heating.

 

Well i have never heard of either of those things. LOL! It sucks being a noob.

 

It's the exhaust heat riser valve. It closes when the engine is cold, forcing the hot exhaust up through the passage in the intake manifold to speed the warmup of the engine.

 

I was just bustin on the new car turbo setups that are popular.

Do a google search for "exhaust manifold heat riser".

If you want to go way back in car history, they had not invented the automatic one like you have yet. Those old cars in the 1920s- had a manual valve that did the same job, but was dash controlled by a cable type knob, like a choke cable. Those were marked on the knob as "HEAT".

 

Cool. Well I am sure there is a reason the engineers put this contraption on the car. I guess I will go through it and get it working.

Thanks

 

If it sticks, I'd just be sure it is stuck in the open position.

 

When it's cold, the spring contracts and closes the flap, directing heat up to the carb thru the intake. When the engine warms up, the spring expands and opens the flap. BTW, if you plug up the heat riser holes in you block at the intake manifold with a couple of pennies, it will make more noise, which is always associated (rightly or wrongly) with more power and speed..

 

It's a left handed smoke shifter.

 

As others said it is a heat riser that helps the engine warm up faster. The danger is they tend to stick shut and cause a restriction on exhaust flow. If you live in a cold climate you probably need to free it up and use it. In South Texas not so necessary.

 

I always remove them. If it is a "correct" car, I die-grind off the butterfly, and leave the shaft, so the outside appearance remains the same. Otherwise, it all comes off, and the holes get tapped and plugged.

 

I disable then as well. They aren't worth the trouble they can cause. I've sometimes found then welded or wired open by previous owners.

 

I generally either cut these out or just weld them wide open. In most older vehicles I come across, these are always rusted shut and it is more trouble to try to replace it than it is to disable it. The whole point of these was to restrict exhaust flow on a cold startup to help the engine warm up faster, thus allowing it to come down off of fast idle sooner thus helping with fuel economy and reducing tailpipe emissions. It was a good idea, when they worked properly...

 

I can see the potential benefit, but as some of yall have pointed out, the down side is not worth the risk. Since it rarely gets cold enough to worry about down here, I'll remove the flap. Easy.