The Stovebolt Site Forums The Shop Area Engine Shop Exhaust Manifold Flapper

Working on a 1956 261. The exhaust manifold flapper rod and weight are frozen. Tried heat and penetrating oil and it is still stuck. The actual metal flapper in the manifold is loose so my question is can I just weld the flapper onto the shaft in the closed position like in the photo? As you can see it is not a tight seal so some heat will get to the intake. Will there be any big negative side effects? Once completed the truck will mostly only see use during the warmer months, spring through fall here in MI.

I would rather not have to cut it all apart and rebuild the flapper and weight.

Thanks

In Michigan? Can't predict motor/carb behavior. Up to you but.........

You have not worked on it long enough. Penetrating oil, a lot. Work just 2 degrees of rotation at a time and axially also. Gradually it will rotate. Emery cloth the shaft near the holes. Vibrate the shaft with an air chisel bump shaft, on LOW air pressure to seep P-oil into holes and break rust particles loose when shaft is both ways vertical. This is a patience only job, no forcing. I see you have sandblasted maybe.

You live in Michigan (I spent my formative years there). You have two seasons. Winter, and the other couple of months (which also coincides with Pothole Season).
You absolutely need a fully functional flapper valve. Without it, liquid fuel will fall out of suspension from the air/fuel mixture, collecting in the bottom of the cold intake runner, then pouring into the combustion chamber where it will fail to burn and thus slip past the rings, wash off the oil film on the cylinders and end up contaminating the oil in the crankcase. Gas contamination in the crankcase will wear out bearings and every other moving part prematurely.
These flapper valves had side clearance allowing for to-and-fro movement of the shaft. Light hammer blows to the weight and and the other end of the shaft may aid it breaking to bond between the shaft and the manifold.
I recommend that you begin the process over again with heat, Kroil, and LIGHT hammer blows to the shaft ends. Once you get even the slightest lateral movement of the shaft from the hammer. Kroil will seep right in there. Don't count on noticing that movement, just heat, hammer, and apply Kroil several times over a number of days. It will free up.

Working thermostatic flapper gave noticeably improved warm up times during TN winters back in the day. Which were kinda like springtime in MI. With the 216 I needed every advantage I could get.

Hey Doug, I agree with the rest of the comments. Even in warm weather mine needs warm-up time or some choke to make it drivable. We know that something was terribly wrong with the past winter, I rode my Harley at least once each month all winter, like they say in the U.P., 9 months of winter and 3 months of poor sledding. I'm just saying that I think you should keep working on the heat riser flap. Let me know if I can help.

I mentioned the importance of a functioning thermostatic flapper valve in northern climates, but it is still important even if you live in Mississippi. Unless you live where it stays 180 degrees F, it will reduce the amount of liquid gas from falling out of suspension of the air/fuel mixture which will cause undue wear.

Thanks all for the replays. I didn't realize how important the flapper was. I just thought it was for old weather situations. I'll keep working on it.

Is it possible to remove and replace them? Or just swap the manifolds? Mine has the weight looking part broke off.

I rebuild the setup with stainless steel. You can get a weight from someone on the forum who is scrapping out a broken manifold, and a seller on Ebay has a new bimetal spring for a Jeep engine that works on a stovebolt for about half the price of that scarce, expensive original part.
Jerry

No one mentioned heat. I have freed several with penetating oil, propane heat and a tap tap tap over several days to a couple weeks depending on how frozen they are. Heat, spray, tap tap tap and walk off. Heat, spray, tap tap tap and walk off. Heat, spray, tap tap... It Moved!

Patience. You're working with a non-replaceable 70 year-old cast iron manifold.

I used a Mapp gas torch and Kroil to finally get mine loosened up, it took a couple of days. The next question is how do you keep it from happening again? I was thinking of using Anti-seize, but that would burn off eventually. Any cures for this?

The clearance between the shaft and the manifold should be sufficient to keep the shaft from sticking, once it's moving freely. Keeping any kind of lube there when it's exposed to exhaust gas is pretty much of a lost cause. I like to duplicate all the parts in stainless steel, so there's less of a chance of the shaft and the manifold rusting together again. Once the shaft and flap valve is removed, using a chucking reamer in a cordless drill motor to precisely align the holes in the manifold and fabricating an oversized shaft is the "permanent" fix. Then make a new flap valve from a piece of 1/16" stainless steel and weld it to the shaft.
Jerry

Most of them that get stuck real bad likely due to the engine sitting for many years without running. Rust never sleeps. Running the engine on a regular basis forces these parts to continuously go through heating and cooling cycles which keeps the shaft from seizing up.
Another cause is when the bimetallic spring or the pin which retains it to the manifold rusts away. The hot/cold cycling continues, but the movement does not. That is when carbon in the exhaust is no longer your friend.

I've actually threaded the holes in the manifold and installed screw-in brass bushings, and then reamed the bushings for a stainless shaft and flap valve. That's a little bit of overkill, but it works. Just don't get the clearance too tight - - - -it needs to be a little sloppy.
Jerry

My 261 was frozen and in bad shape. I got it out and put in brass bushings.