VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 36 exhaust manifold heat riser

There is an August Chat thread with pictures of a 37 heat riser and how it works. But the 36 looks different. How does it work?

One of the manifolds I have for 36 has a different style weight--it is on a stem with a square weight on the end. Also it looks like there is a hole to hook a spring to pull down on the stem.

I had a new heat riser and shaft (using the old flap valve) put in by a our college machine shop, but it doesn't have the weight. I was thinking of cutting the weight and stem off the old manifold riser (rusted solid and pretty useless)and and welding it onto the shaft. How should it be weighted--to pull down to keep closed when cold? How would a spring be used? Could the riser function without the weight?

In what direction should a new heat riser coil be installed (which way turn)? I have a NOS coil to use. I realize it would expand as it gets hot.

And finally, the last pesky question, is there a good way to keep the new shaft from rusting up? Once on the car, there doesn't seem to be any way to get lubricant to the back of the manifold. There aren't any bushings--just steel shaft with the hole machined to fit.

Thanks!

The round weight is towards the engine side of the manifold. When cold the weight is up and the flapper valve is straight up and down. This sends the exhaust into the heat box under the carburetor. When hot the thermostatic spring become weaker and the weight pulls the valve around (counter clockwise when viewed from the left side of the manifold) and blocks the heat from entering the heat box around the intake under the carburetor. If the valve is checked from time to time and lubricated if necessary re-sticking should be no problem. I have never had one of mine stick in the 40 years of playing with the ols cars. Also duming some Marvel Mystery Oil thru the throat of the carb. with the engine running lubricates the shaft from the inside out.

I will email you some pictures tonight or tommorow that might also help with some of your questions.

Those heat riser shafts do nothing but seize. Mine seized and everyone I ever spoke with had the same problem. My stainless steel replacement parts, made in my home shop and installed decades ago, have fully and permenantly solved the problem.

I'd be glad to email you all the details. If that would be helpful please contact me at rwaldbaum@aol.com

Thanks to everyone for the good information! I have several 36 exhaust manifolds-on one the weight is round, on the other it's square. I probably won't take things back apart to have stainless steel installed, although I'm sure that is the best. As Gene mentioned, I'll plan on turning it after it cools from a drive and every so often in between.

But it would still be good to see how it was done, so will send you an email when get a chance. The community college where I work machined and put in the new shaft for me for free as a student project over a year ago.

Leagl--thanks for the offer on the pictures-yes I would like that. If you get a chance to send them, my email is chev1936@gmail.com. I'll try to find some way to reciprocate.

How or why would a spring be set up to pull down or up on the weight? One manifold has the lever/weight with a small hole that looks like must've been for a spring to hook into (if memory serves it is the square weight). It looks factory.

I don't have the parts handy--I will be working on the car again in a few weeks. The car is at my parent's house about 80 miles away. But I'll try to take some pictures if that will help.

Thanks again!

The 1933-1936 heat riser shafts are rather difficult to lubricate when the manifold is installed on the engine. The fact that each year before winter storage I pour M.M.O. thru the carb. with the engine running and kill out the engine allows the oil to leak thru the shafts. Sitting this way "well oiled" all winter perhaps helps to disolve the rust.

leagl...

If you'd be so kind as to forward me those heat riser photos, I'd be forever grateful! My 36 1/2 ton pickup has the same disease with parts missing. Thanks for your help.

Bruce
footbiz@sbcglobal.net

I read your post on VCCA helping with a heat riser problem which seems to be endemic to the chev "6" engine, and I'm no exception. Would you be kind enough to forward to me the details you employed to solve your problem? thank you so much. Bruce Smit


Hi Bruce. I did this job about 30 years ago but I think I remember the details. The problem is the heat riser shaft rusting and seizing in the exhaust that is also rusting. When metal rusts is swells, so this problem is ubiquitous.

I removed the exhaust manifold then did the following:

1. Ground off the heads of the rivets that hold the heat riser plate to the shaft and removed the rivets.

2. Ground off the upset (mushroomed) end of the heat riser shaft that retained the weight lever at the inside (engine) end to release the weight lever.

3. Duplicated the heat riser shaft in stainless steel. This was very easy, requiring a slit in the outside end for the spring, a flat and 2 rivet holes to accept the original heat riser plate and 2 short flats on the inside end for the weight lever.

4. Drilled the manifold heat riser shaft holes oversize and made 2 bushings of stainless steel very slightly oversize for a light press fit in the manifold and about 0.004 oversize from the shaft to allow free movement even after the heat riser plate and shaft got hot. My metallurgist father in law reminded me that stainless steel has a very high thermal expansion rate and he calculated the required clearance based on the dimensions of the parts and the anticipated temperatures.

5. Installed the new bushings and shaft, riveting the plate and peening the inside end to retain the weight lever just like original.

Bruce, none of this required any special skills. I never even took auto shop in high school. In the decades since I made this modification the heat riser has worked perfectly with zero maintenance.

Finally, I want you to know that in the decades since I have completed this project and described its simplicity and success to VCCA members, you are the first to ask for the details. All of the others shrug and accept a seized heat riser as "normal". Interesting, huh?

Ray Waldbaum

Thank you, Ray. I am a purist at heart - I appreciate your help. A friend gave me this truck, and I have had a blast trying to find parts as well as make what was original equipment work properly. 1936 is a tough year. I'll let you know how this project works out!!

Both my '33 and '36 manifolds had nothing left inside. The deflector plates were gone. I just decided the heck with it, deleted the gasket, and made a flat plate out of 1/8" steel and installed it between the intake and exhaust manifolds and sealed it with Hi-temp RTV rubber. This works great in California where you really don't need to heat the carburetor incoming air anyway.

1936chev and footbiz, I emailed pictures over the weekend. Did you get them?

Got my pics yesterday.............thank you so much. I needed to see the return spring location on the block side of the manifold, etc. Know where I might find a weight and heat sensitive spring to trip the riser? How much weight is needed to make this mechanism work properly?

It will not "work" at all with out the weight. The weight pulls the lever its mounted to down and closes off the heat when the thermostatic spring heats up and loseses its tension. The little coil spring is merely an anti-rattle spring.

Thanks leagl--I got the pictures as well. But just now getting back to check. Much appreciated--they will help a lot. I may reconsider and at least put in stainless bushings if I can find a size to fit and can drill out the manifold.

Would copper or another non-ferrous metal work as a bushing? On second thought, they may be too soft and wear prematurely. Since the shaft has already been made and fitted in plain steel will keep that.

And thanks Gene for the info about the spring.

Leagl: I would really appreciate It If I could also get a copy of the pictures. I am missing the plate and need to make a new shaft.
Thanks,
Richard

Leagl, please sent the pictures to me too. My is bad also.
Thanks, Mike

Thanks (Larry), Leagl, for providing very detailed photos of your exhaust manifold heat riser fix. Much appreciated.
Richard