The Stovebolt Site Forums The Shop Area Engine Shop heat riser

I bought a 235 with a missing heat riser on the exhaust. The weight, shaft,sping and flapper all are gone. I wonder about what do you all do for this? I want to stay stock, fentonless. If any one can throw me a bone on this I would be grateful. Thank you.

mother dear, what i did on all my trucks was to remove them and plug them. i used helicoils and little allen plugs in the helicoil to seal it with a dab of hi temp rtv. should you go that route before you drill out the existing holes for the helicoil make sure you first remove the hardened sleeves that the shaft rode on. find the edge of the sleeve and colapse it and drive it out.

What did you do to heat up the carb? Wont it run like a Kia if you don't heat it?

nothing, i just have it warmed up before i take off and its fine. i dont run my stuff in the winter other than to jockey trucks around the shop. the rest of the year theyre fine. they run like new GMC's and CHEVYS

I would track down another compatible 235 manifold with a working or almost loose heat riser system. I would also have the manifolds trued up at a machine shop to any grind warpage out of the exhaust manifold. With some new gaskets, your system will be like new and do what it was intended to do without a buntch of leaks.

Chevrolet engineers spelled it out pretty good in the shop manual as to why it’s there and what it does:


“As the engine warms up the thermostatic spring closes the valve and directs exhaust gases away from the manual as shown in figure 3. This thermostatic control results in the proper temperature of the incoming gases under all operating conditions. The tension of the thermostatic spring is very important. When too tight, the heat will not be turned off of the intake heat riser as the engine warms up, with the result that the incoming gases will be expanded several times greater than normal and it will become impossible to get a normal fuel charge into the cylinders. This condition will reduce power and maximum speed and will cause detonation as well as sticking valves.”


http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0604.htm

Find another manifold and make sure it functions as designed for best results.

Even without one you still get heat to the carb & intake manifold. If you are in a warm dry climate you can do without it. If you are in a cold or damp area you should have one.

i belive chevs of the 40's sell a new shaft, spring, and plate to install. only i think you have to make the hole for the shaft bigger. it might be easier and cheeper to find a used manifold.

Thank you elhippie.