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The metal flap within the exhaust manifold is rusted and does not move…think I could get to it by separating it from carb base..but these bolts don’t budge..tried pb blast and heat…afraid I will break off heads…probably 83 years old…any other suggestions ? Tks..

Heat, and lots of it. Or induction coil.
And yes, its gotta come apart to get the flap released from the shaft, its pinned in the middle.

Tapping lightly with a small hammer on the shaft ends, first one side, then the other, over and over again will often loosen a badly stuck shaft. If you can get all the oil off the parts, soaking the shaft with Blechewhite or CLR as you tap on it may loosen it. Try to get the liquid on the shaft ends and inside the manifold and keep it all wet with the liquid while tapping the shaft endwise. I would avoid separating the manifolds if at all possible.

Also avoid tapping on the weight itself. It's brittle and can easily break.

Is separating the manifolds a bad idea… should I just leave flap frozen…I don’t even know what it does? It seems there is just a paper gasket sealing them..

You don't want to leave it stuck in the shut, or cold position. As mentioned above, don't tap on the weight, just on the shaft ends, and don't tap it hard enough to damage it. If you are patient, it will come loose. CLR and Blechewhite are mild acids, and they will eat rust. Applying some heat from time to time will also help. The gasket is asbestos, and you probably can't get another one. If you apply heat, apply it to the shaft and keep it just under a red heat. Don't breathe the fumes and dust. Once you get the shaft loose, you need to check the manifold assembly for flatness where it attaches to the block. It is probably warped, and if so,it can be resurfaced. Doing so will prevent leaks and cracks and blown gaskets. Patience, not brute force, will get results. If the joint between the intake and exhaust manifolds is still tight, I would not attempt to take them apart. Doing so won't do anything to loosen the shaft. Twisting the shaft is not likely to loosen it. Tap on the ends of the shaft to move it endwise, like driving a nail. Light tapping, over and over, plus the chemical solutions, will eventually loosen it. The shaft assembly is designed with end-play, and it will move endwise for about 1/8" if it is free.

I've had great luck using lock-ease to get those shafts to free up. If the engine is running, spray liberally, warm up the engine the next day, and try gentle persuausion with the manifold warm.