The Stovebolt Site Forums The Shop Area Engine Shop Heat riser spring

I've repaired my heat riser and got a new spring for it. When you apply heat to this spring, it contracts and curls tighter. When it does this, it unhooks itself from the peg in the manifold. It seems like what it ought to do is expand. The shaft moves freely but I can't get the spring to close the valve. I'm wondering if I have a wrong or defective spring. Should it expand or contract under heat? I got it from Classic Chevy Parts. For some reason, I've had a run of lousy or wrong parts from them. They even sent me a speaker that I didn't order and didn't pay for. They were mystified when I called to tell them about it.

The heat riser spring should curl tighter as it gets hot, thus opening the heat riser valve. Be sure that you didn't install the heat riser spring backwards, if that's possible. In the correct position the end of the spring that goes on the peg should be facing the engine.

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above is how its set up on my 50

Yes, it is possible to install the spring backwards. If it unhooks there is something wrong. That would indicate expanding rather than contracting. Do you have the shop manual? Read it, the information is invaluable. If you are like me, after reading through the manual you realize how much you don't know. Get a Motors manual, buy an asembly manual, read them, as they are all great reference books. That is the very most basic information you can have. Even after installation you need to fine tune the spring.

http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0604.htm see the info under fig 3.

This subject is right in time for me I'm struggling with this on two different trucks, both have good shaft movement on their own but no matter how I attach the spring I get no movement. When I had the manifold for the 261 on the bench evereything moved fine when I applied some heat to the spring but mounted to the engine with engine fully warmed up I get no movement and the flapper does'nt close! the other truck same thing, no spring movement when the motor's hot. Is it possible the springs I bought are bad?Any suggestions?

Thanks for the responses. It looks like I have the spring installed correctly according to the manual and the pics posted by others. I've posted a picture below. I think the spring is wound too tight and needs to be spread out some. What do you all think? When I apply heat, the first thing that happens is the hook part of the spring lifts itself off the peg. The shaft does not turn even though it's free and will rotate easily by hand.

[IMG]http://i7.photobucket.com/albums/y261/bohon/56%20Chevy%20truck/HeatRiser009.jpg[/IMG]

And I just read the section from the manual posted by Forty9, which is great information. I overlooked it when I looked at the manual. Too busy looking at the pictures.

Joeflanagan

It looks like your loosing spring movement because the shaft is not crimped closed to the spring tang. Compare your pic to mine above.

You may just have to crimp the shaft end around the spring so there is no gap.

Be careful . The shaft may be brittle and can easily bust. Replacement shafts are availiable.

I was wondering about that. I fabricated the shaft and didn't have anything that would cut a slot as narrow as the original. I won't be able to pinch it shut but I can probably use something as a shim and get the same effect.

Try giving it some throttle and watch your counterwieght.
I warmened my engine up in the garage and the valve didnt move. I grabbed the throttle rod a goosed it a bit and it moved closed,Heat off.
Checked it after a short drive and it was still closed or heat off.

In my case, I don't think I have the counterweight positioned correctly relative to the plate. Luckily, the plate is just a press fit on the shaft at the moment and I can move it around. I think the way I have it right now, the spring might be fighting the weight.

Here is how the weight should be when hot

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Here it is cold at rest
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One problem I found on my counterweight is the it was hitting the manifold. I had to dress the manifold down for it to clear.
in the earlier video I posted you can see a smooth area of the manifold where it was hitting before I ground it to clear


Just something else to look at.

Thanks, Dads. It does look like a tight fit there against your manifold. When mine is in the closed position, the outer edge of the plate (the tongue-shaped portion that is furthest away from the engine) makes contact with the manifold so that it doesn't close completely. There is about a quarter inch gap that is left open. I don't know if this would have a negative effect or not, but I was considering grinding the plate down so that it no longer hits the manifold.

joeflanagan:
I see from your photo of your homemade heat riser shaft that the slit is too wide and doesn't make tight contact with the spring.
That is your problem. To fix it you must close up the gap so that the end of the spring fits snug in the slit.

Thanks. That's the next thing I'm going to do.

Thanks I would have never thought to try that!

Hello and Happy New Year,

Jumping into this old coversation as I find myself having the same issue with my heat riser.

Installed a new Spring (Heat Riser Shaft moves easily) in the slit on the other end of the counter weight. The spring is snug on the shaft. I did look over the manuel and mentions to not over tighten the spring and only give it 1/2 a turn so the one end rests up against the manifold peg.

So when I installed the spring, I have the Counter weight in the HEAT ON Position, slide the spring where I can then apply some counter clockwise pressure to the spring to slide it past the peg. All looks exactly like it is pictured in the manuel, however when I take the truck out for a drive (3100 53 Chevy Truck with 235), the heat riser stays in the HEAT ON position. When I park it back in the garage to look at the engine, I do notice the Heat Riser jiggles a little like it wants to turn off, but never does..

Any suggestions?

Here is some pics that I took:

Take a heat gun to the spring and see if you can get it to back off. Could be on backwards or the manifold is not getting it hot enough.

I just went through this a couple months ago on my 50 216. It was driving me crazy why it wouldn't work trying to hook it up like the picture in the manual. I finally flipped the spring around, and now it works perfectly. It was a little harder to get the spring on the offset slot in the shaft, but that was what it took to make it work correctly.

Forgive me for bringing this one back to life, but I just wanted to clarify something. I am having similar problems with the spring moving the weight. When I heat it, the 'arm' of the spring stretches back from the peg, but the flap/weight doesn't move. It moves very easily by hand though. My question is, should the counter-weight always be working against the spring and trying to close the flap? If it did, then I would expect that it would work as it should. Any fixes to getting the weight to put more pressure on it? Perhaps some sort of lube? What can take the heat? Thanks!

Goose the throttle and see if the weight goes where it belongs in the warmed up position and stays there when the the engine returns to idle. That is all that needs to happen. The exhaust pressure forces the flapper to the warmed up position.

I'm rebuilding the carb at the moment, but I found that the engine wasn't really heating the spring enough to get things moving. It elongates off the pin with a heat gun though. I have seen the throttle cause it to move, just haven't witnessed it staying open before. Things got hot the other day and I believe the fuel boiled in the bowl, which never happened before the new spring. I will try it again, I was just curious if all the weights stayed in the horizontal position, without any spring pressure applied to them.

Here are 3 images I made for a gentleman in Germany. On mine, the weight falls naturally when the spring gets warm. It rotates counter-clockwise as shown. Good luck.

In the second image (above), I'm holding the weight as it would be when hot. The first image is where it sits when cold.

Thanks for those Jon, that's how my setup looks, I will have to play with it a bit I guess.