Central Boiler CL5036 draft door replacement

[Joacchim]

My 15 year old CB has been running hot and by the looks of the smoke exiting the stack when firing isn't being called for, air inleakage is the cause. I replaced the door bolt rope last year, same symptoms. Burning lots more wood than I'd like.

Long story short, spotted gaps in the draft door when it's supposed to be closed. Removed it and found the mating surface to be quite worn - this must've been going on for awhile. I bought a new draft door but when I went to install it, I could not achieve a good seal with the boiler door where it's mounted. I cleaned up the surface with some mild touches with a file to eliminate high spots, but the upper portion of the flange will not mate with the new flapper. I suspect the main flange is worn as well, and assume the proper fix would be to replace the cast iron door. (Photos of old and new flappers attached.)

I'm hoping to avoid that. Has anyone tried using a high temperature epoxy to build up this sort of mating surface, to assure proper contact? My thought is to apply a thinnish film and then cover it with wax paper, then allow the new flapper to close on it, making sure there's a good seal all around. Once the epoxy is dry I'd remove the wax paper and hopefully the top of the flange with the epoxy holds up.

If this is a bad idea, any others? Thanks.

 

[brenndatomu]

Didn't those have a lifetime warranty door? I know CB backed out on the lifetime part then, but I thought you could still get at least one new one...maybe not?
When I coated my door gasket with silicone (like how Heat Master does theirs) I covered it with aluminum foil and lightly closed the door on it to custom form it...just left it there then.

 

[Joacchim]

After 2 days struggling with this I decided to compare the old flapper door with the new one. I found the "hinge arms" didn't have the same angle, and that was preventing the flapper from making a good seal. Luckily they're a fairly soft metal and I was able to bend them to match the old hinges, without distorting the flatness needed to make a good seal. Here's a couple more photos to clarify the issue.

Thanks for your reply.