VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1933-1936 35 master heat riser shaft

I've seen on here and elsewhere, where people have made new shafts for the heat riser. I am in the process of restoring one now and could use some specs on the shaft. Length, orientation of the slot for the thermal spring compared to the block off plate. Orientation of the "flats" for the counter-weight compared to the plate.

Thanks in advance!

Maybe some will jump in here who has a '35 especially with some photo's.

"I've seen on here and elsewhere, where people have made new shafts for the heat riser."

Good morning Doc.

When I made mine I also put stainless steel bushings in the manifold. I'd be glad to describe this to you in more detail privately.

Ray W

Yes, please.

Thank you

Good morning Doc.

I did that job about 40 years ago and it's been together and working perfectly all that time. If you're starting with no parts I could send you a couple of photos to accompany the description of what I did. To do that I'd need your email address.

Ray W

Doc@bowtiecars.com

Good morning doc.

I sent you an email with a couple of photos and a link to a discussion of your issue on the Stovebolt forum.
Some will argue that a heat riser is unnecessary. They are certainly entitled to that opinion.

Ray W

I remember reading years ago in a factory shop manual or maybe just something like Motors Manual about the proper way to lubricate the heat riser. You were to take a cup of kerosene and mix graphite into it. Then by using a brush, you would apply to the shaft. The kerosene would wick the graphite into the joint. The kerosene would then evaporate without residue, leaving the graphite as the lubricant. Sounds reasonable to me, since the graphite would never burn or solidify.

"I remember reading years ago in a factory shop manual or maybe just something like Motors Manual about the proper way to lubricate the heat riser. You were to take a cup of kerosene and mix graphite into it. Then by using a brush, you would apply to the shaft. The kerosene would wick the graphite into the joint. The kerosene would then evaporate without residue, leaving the graphite as the lubricant. Sounds reasonable to me, since the graphite would never burn or solidify."

36Phaeton,

In my experience neither the graphite/kerosene cocktail nor any other lubricant works long term. That's why I made a stainless steel shaft and stainless steel bushings pressed into the exhaust manifold. That was about 40 years ago and the heat riser on my '36 PU has been totally stick-free ever since without any lubricant ever being needed.

I got that idea from a Dodge part. I have a '71 Dodge van that I bought new and a dealer part for it is a "kit" for the heat riser valve that includes a new stainless shaft and stainless bushings. It's installed easily and quickly once the right side exhaust manifold is off.

Ray W

Thanks for all the help. I had a machinist cut a new shaft for me and it works very well. 1935 Heat Riser New Shaft Test

Good morning Doc.

Shouldn't the valve open with the application of heat rather than closing? I did that job over 40 years ago so I don't remember any details.

Did you also put stainless bushings in the manifold?

Ray W

The manifold valve needs to close off the passage to the intake/carburetor when hot. That increases the vaporization of gasoline when cold and reduces the potential for excess vaporization of the fuel when hot.

"The manifold valve needs to close off the passage to the intake/carburetor when hot."

Thanks for refreshing my memory on the movement of that valve Chipper, vertical when cold and horizontal when hot. I had mine opened up and made new stainless steel parts for it but that was decades ago. I guess that's a good thing that the problem was totally solved and forgotten because it required no further attention.

Ray W

Yes, Chipper is correct. This one was rusted stuck in the "Cold/Open" position. Driving in the summer would not be very fun. Vapor lock, fuel boiling out of the carb, hard to impossible hot starts, etc....

We chose to use brass bushings (for no particular reason). It will be a good experiment to see how long it works.

Thanks again for all the input and help!

"We chose to use brass bushings (for no particular reason). It will be a good experiment to see how long it works."

Good morning Doc. Happy Friday.

Brass is an interesting choice for that application, Are you sure they're not bronze?

Bronze is used in valve stem bushings but it seems that is a much lower temperature application. It's hard to imagine anything on an engine hotter than the exhaust manifold heat riser, since it is constantly directly in the exhaust gas stream. Even the exhaust valve is cooled by the valve seat and guide.

When my now-restored '36 PU was a sbc powered "rat rod" about 50 years ago I had the headers flame sprayed with aluminum for rust protection. Little beads of aluminum formed showing that the aluminum coating was actually melting locally near the ports during running. That's how hot exhaust manifolds and headers get.

Ray W

When I was about 16, I rebushed a Chrysler heat riser with brass. A few days later I discovered the bushings were missing.

"When I was about 16, I rebushed a Chrysler heat riser with brass. A few days later I discovered the bushings were missing."

Bloo,

I bet that made some noise! Based on your experience, if I were Doc I would pull those "brass" (probably actually bronze) bushings while the manifold is still on the workbench and replace them with stainless steel bushings. I'm a geologist, not a professional mechanic, but I've never seen yellow metal bushings in a high heat application like that, stainless steel only. My stainless bushings have been in for about 40 years with no leaking, binding or sticking.

There is a reason why the heat riser repair kits Chrysler used to sell for engines like the one in my '71 Dodge have stainless bushings. That reason is probably that only stainless works!

According to this chart the maximum operating temperature of a bronze bushing is 750* F (intermittent to 1200* F)

https://www.nationalbronze.com/News/cast-bronze-alloys-operating-temperatures-and-hardness-ratings/

I know from melting flame sprayed aluminum on headers that even header tubes get hotter than 750* and even hotter than 1200*. Aluminum melts at about 1220*. The header tubes or exhaust manifold are way cooler than the heat riser parts for the simple reason that the outside of the header tubes or exhaust manifold is in contact with ambient air and the heat riser is in the super hot exhaust stream.

Doc, if you live in a rural area that would explain the machinist not knowing that yellow metal is not suitable for extreme heat applications. When I moved from a metropolitan area of California to a rural area about 20 years ago I was astonished at the difference in general competence between the two areas. Just getting the mail and newspaper delivered reliably and the trash cans emptied is hit and miss here. I can only imagine what it would be like getting competent machining service.

Ray W

Thank you all again for the help and suggestions. I will have the bronze bushings replaced with stainless next week. I have to go back to the machinist and pick up the shaft again. Once we found it worked as it should, he wanted it back to take complete measurements for possible duplication.

I did find a great tip on coating the exhaust manifold. With even high temp paint, it usually fails fairly quickly. It was suggested to coat the manifold with spray on graphite lube. The carrier evaporates off and leaves a very nice matte dark grey that does not come off or is affected by heat. Easy to touch up, just rub some more graphite on.

Graphite worked for me . I had some old powdered graphite and mixed it with some lacquer thinner to brush on.

Dick

"Graphite worked for me . I had some old powdered graphite and mixed it with some lacquer thinner to brush on."

Dick,

That's a great suggestion. How durable is that graphite coating?

"I will have the bronze bushings replaced with stainless next week. I have to go back to the machinist and pick up the shaft again."

Doc,

What's the guys excuse for not using the correct material the first time? Is he a "professional" machinist or a hobbyist like me with a home machine/welding shop?

Ray W

Ray,

The bushing choice was on me. They put in what I had asked for. They have done other projects for me in the past with great results including fabricating a manual valve for a 54 Powerglide I rebuilt.

Good morning Doc.

Happy Father's Day

I think you will really like the way that heat riser works with both the shaft and bushings stainless. I wish I could remember the clearance but I've forgotten after all these decades. My father in law, a metallurgist and chemical engineer, calculated the proper clearance based on the shaft diameter, anticipated shaft temperature and anticipated bushing temperature and I made the parts with the clearance he recommended. His recommendation was obviously "dead nuts" accurate because even to this day the fit is perfect.

To me, it's these kinds of projects that make our hobby so interesting.

My present project is making a firewall-electrolock rubber bushing with an angled cable hole because, at least on my '36 PU, the cable comes through the firewall at an angle that deforms the bushing that was an original part I used when I restored the '36 in the early 1970s. I know the vendors have China repops of that bushing but I'm starting with a quality panel plug and adding an angled hole to it. The challenge in that is making the hole without tearing the rubber or otherwise damaging it.

I'm not allowed to post photos here because I'm no longer a VCCA member so I can't show you the fixture I've made to compress the rubber plug during the hole making process.

Ray W