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Just curious.....

My heat riser is stuck and not moving. What effect does it have on my motor? Will it cause a restriction on the exhaust? Since I don't know enough about the effects of it stuck open verses closed or exactly what it does, I don't want to modify or fine tune anything until I get it unstuck and better working knowledge. Thanks everyone! Engine 1951 216 with Rochester carb.

Chris

Manifold heat riser and heat control valve. describes the function/purpose.

If you're patient, you might be able to get it to free up with some penetrating oil. Soak it real good and carefully try to work it back and forth. Sometimes they will free up and sometimes not....

I had to split the manifolds on a GMC 228 and remove the valve and shaft by grinding off the spot welds. I used a new 5/16" shaft with brass bushings, then re-welded the valve back on the shaft and re-assembled the manifolds. On my 235, some penetrating oil did the trick.

Do you have the spring? It's heat sensitive and controls the opening and closing of the heat control valve. Let us know how it goes, good luck.

Thanks Tim! That explains it exactly and now I understand it better. My truck must be stuck in heat on position. Once it is warmed up, I start to lose power under load (hill or acceleration). I am also having to adjust by moving the choke to smooth out running. I will work on getting it freed up to see what happens. Thank you, thT was very helpful!

Chris

Since I was using my phone, I didn't see iyour post right away. I scrolled up read it and then as I was deleting my old post. You posted the above message. You just beat me to it! Thank you again!

Every day, spray the shaft with penetrating oil and give the counterweight a few light taps with a hammer. Tap side-to-side rather than torquing the valve the way it is supposed to turn.

There is a bit of "end-play" in the shaft, and after a few days you should begin to see movement. After it starts to move then you might try twisting it gently. You don't want to break anything.

You could also try heating the shaft occasionally with a propane torch. The expansion of the metal might break free some of the corrosion.

Thank you my friend to the north! I am spraying it a couple times a day. Where in Saskatchewan are you? I grew up in nd and drove to Regina many times. I also have a coworker that played hockey up in that area.

Chris, handy-andy has it right. My was stuck bad on the 261 and I had to rebuild mine.
During that time some told me it didn't have bushing but it did and I'm 99% sure it was original.
The shaft was gone and the bushings worn out. I did as Andy. I drilled out the roll pin holding the shaft to the counter weight and replaced shaft which I got at Ace Hardware...and I also got the bushings from Ace as well.
To make it all fit nice I was also able to drill the holes for the bushings out a little. The fit was great.

One thing to pay close attention to if you take it all the way out is the location/position of the two little tack welds that hold the butterfly on the shaft that you grind off to get it out.
Here is an old picture of mine...I can't seem to find the others where I put it back together. Hope all this helps in some way.

http://i140.photobucket.com/albums/...xhaust%20Riser%20Damper%20repair%202.jpg

Well gents, I got it moving without as much effort as I thought. After 2 days of spraying with penetrating oil, I tapped the shaft with a hammer and I was able to move it by hand. I wil keep doing this to ensure it is moving very easily.

Nice work.