Hi_ I have the intake and exhaust manifolds apart and find the flapper in the Ex manifold stuck tight in the closed position-vigorous tapping of the shaft does not loosen-am thinking of just removing the flapper and reinstalling on the shaft in the open position rather than going through the drill out the shaft more time consuming repair approach.. Looking for opinions pro and con. Mostly from people who have put the flapper in the open position. I'm concerned about engine overheating if it leave the flapper in the closed position which causes exhaust gas to always go through the intake manifold.
Thanks for your help and comments.
Martin Lum
1935 Chevy standard

I have spent the time to free up the flappers in several manifolds. Alternate heating and cooling with occasional liberal application of PB Blaster and light tapping with trusty ball peen hammer has worked every time. In most cases once you get all that dadblamed rust out the shaft/flapper works great.

Martin,

I've done three of the manifold heat dampers, and the method that worked best for me was to separate the intake and exhaust manifolds. Caution: This can be a challenge in itself, as the 3/8" bolts, studs, and nuts may be seized and break off when you try to remove them. Then you have the problem of trying to drill out the broken bolt/stud and re-tap.

Assuming the manifolds separate OK, you can now see the heat damper. You'll notice there's about 1/16" total lateral clearance between the sides of the damper and the walls of the exhaust port. When the damper shaft is free, the damper and shaft can be moved slightly from side to side. With the manifolds separated, you have good access to get penetrating oil (recommend PB Blaster) onto the shaft, both inside and outside the manifold. Using a hammer, tap the shaft laterally in both directions, keeping it wetted with penetrant. Don't hit it so hard as to mushroom the shaft end or bend it. Once you get the shaft to move laterally, you're pretty much home free because this allows the penetrant to soak in along the shaft. After you are able to tap the shaft back and forth laterally, apply a light tapping to the damper counterweight to rotate the shaft toward the open direction. If it rotates slightly, tap it back toward the closed position. Continue tapping the counterweight back and forth. Soon, it will become looser and you'll be able to rotate it through its full arc. Continue rotating it back and forth while feeding it penetrant. Once the rust is disolved by the penetrant, the shaft will rotate freely and you should be able to resume full automatic operation if your bimetallic spring is still in place.

If you're reluctant to attempt to separate the manifolds, you can still use the same method--you just don't have access to get penetrant to the inner part of the shaft, and you can't see where your lateral clearance is in order to know which way to tap the shaft ends. Even so, if you're patient, you can probably get it freed up using the above procedure.

Mark

Once you do get It apart, and assuming all the parts are there, It Is quite easy to redo the shaft In stainless. I can send you step by step instructions.
Richard

Shouldn't this thread be in the 1933-36 forum?