Heat riser

[plymouth71]

Could anybody tell me the purpose/function of the heat riser on a slant 6?The one I have is froze up and does not operate and I was thinking about removing it.Noticed when I was running 50-60 mph and let off the gas I could smell an "old gas" smell and I was told that the heat riser butterfly may be stuck in the closed position.Any help would be appreciated.

 

[Inertia]

The heat riser's job cold,, was to direct hot exhaust gas up to the carb base,, to help prevent a conditions called "carb icing", where the throat of the carb would get covered in ice (snow) to the point it would plug the idle circuits.. causing stalling , (usually at the second and third stop, after a cold morning start)... this would persist until there was enuff heat around the carb to melt the snow..(this happened in hi humidity mornings)

When hot, a thermal spring or vacuum pod would open the valve to direct exhaust straight out the pipe..

 

[slantsixdan]

Removing it will worsen your driveability and fuel economy. Many people misunderstand the purpose and function of the manifold heat valve. Read this thread to get educated.

 

[BillGrissom]

Most likely, the internal plate is corroded away, so unlikely it is restricting the exhaust. Mine was stuck solid decades ago, so removed it and plugged the shaft holes w/ stainless bolts & nuts. I did this when the manifold was off. I sure wouldn't remove the manifolds just for this issue. Of course, try solvent first. If you can't get the correct solvent from a dealer, maybe try wood stove glass cleaner. It dissolves soot, which is probably the same problem. You can find at Ace. I lived mostly in the SE with my slant, but did have it 2 winters up North. I don't recall any problems starting or driving in the cold, and I think the riser was stuck then.

 

[plymouth71]

WOW,I didnt think there was a whole lot to the heat riser but now after reading all of the replies I think I will try to free it up,Thanks to everybody on the valuable imfo and advice.