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

OK, I know that the stuck heat riser has been discussed for years on here. My only question is: Will I damage anything if I heat the exhaust manifold up good and hot around the shaft area. I would like to try that before I give up, but I don't want to trash anything in the process.

That is what finally worked to free up mine; some heat, a little lubricant and some taps with a hammer got it loose. I don’t think you can hurt it with a propane torch; it gets pretty hot from the exhaust too.

Lee.

I wasn't really thinking about propane. I was planning on trying acetylene, which gets much hotter. I've been soaking it in Kroil and liquid wrench for several days along with light taps from a brass hammer.

Full throttle exhaust gas from most engines under load approaches 2K degrees F. I've confirmed that on numerous dyno runs with exhaust gas monitoring equipment in the ports. A valve that operates in that environment for thousands of miles and decades of time isn't likely to be damaged by a little heat from a torch, unless you get outrageous with it!
Jerry

I had been working with just the spray stuff and a hammer for several months with no luck until I went after it with the torch (all I have is the propane). I don’t recall if I had tried the spray and hammer trick just after a hot drive, that might help. I did have the manifold off when I finally got it freed up, so I was able to spray both inside and outside of the shaft. Also I did not have to worry about igniting the fuel in the carb at the same time! That reminds me, I need to lubricate it again to make sure it does not seize up once more.

Most oil based lubricants won't help a heat riser, due to the heat in that area. The residue left behind when the oil burns away can gum things up. You might try some Never-Seez, which is made from atomized aluminum powder and very high temperature grease, or powdered graphite in a squeeze tube that is usually used to lubricate lock cylinders.
Jerry

Mike- I just went through this problem on my '51's 1956 235 heat riser valve. I started on it last fall, spraying, tapping (then beating), heating it with propane and then switching from PB Blaster to Kroil, with no results. Then someone mentioned that he had gone a different route by disconnecting the exhaust at the manifold and working on it from underneath. I hadn't even thought of that, and was ready to pull the whole manifold system and carb off to get to it from the top.

But after dropping he exhaust pipe, I found that I could shoot the Kroil up into the rod and valve points and do a little gentle prying on the flap (it still didn't budge, yet).

But after getting the oil on the inside mounting and stuck surfaces, and THEN tapping the counter weight and rod end at the spring attachment point, and also removing the oil filter casing for a better shot at the weight end, I felt a little give. After that, it was just a few minutes of tapping backward and forward and re-spraying the Kroil before I noticed a little give, then some more, then some more. It was moving, but wasn't moving freely, so I sprayed all points, on top and up through the bottom again, then grabbed the weight with my channel locks and moved it manually until it finally moved free enough to return to it's open position each time I let it go. I then sprayed the heck out of all points again, and it seems to be working like a champ now. I just got my new bi-metallic spring, exhaust gasket and new oil lines in yesterday, so I'm getting ready to put it back together today or tomorrow. But that thing was stuck tight. I thought it was more to do with the flap inside being rusted to the manifold, but after I got it away from the point of contact, I still had to keep shooting kroil on the rod connections inside and out.

Can't remember who suggested going through the exhaust pipe connection (Keith, maybe?), but I thank him for the idea. It worked for me! Lee Butcher

I completely removed mine and threw it in the vinegar for a couple weeks. Still stuck. Threw it in some baking soda and water to stop the acid. Still stuck. Forgot about it for a couple more weeks and grabbed it when I went to wash something else. It was free as a bird???