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Posted by: DennisV Sep 10 2022, 12:51 PM

How are folks going about restoring original flapper boxes?

I had intended to bead blast and powder coat ours. Preparing to degrease them today, I see that they have a spring mechanism inside and what I think is a rubber sealing ring. I don't think those would much like the powder coating and required heat. Some other http://forums.pelicanparts.com/porsche-911-technical-forum/589980-cleaning-flapper-boxes.html get disassembled, but I don't see a way to get those components out without destroying the housing.

Perhaps bead blast and spray can is the best bet, and just accept the spring and sealing ring will get painted?

Thank you.

P.S. I've seem some http://www.914world.com/bbs2/index.php?s=&showtopic=310934&view=findpost&p=2491707 rather than black. Was that ever definitively answered? The color of ours is rust.

Posted by: Mikey914 Sep 10 2022, 05:01 PM

May want to rethink the powder coat for this application. Unless you have a higher temp version you are running. Enamel works well here. They will see a fair bit of heat. A ceramic coat material is also a good option.
The powder may work, but over time it may get brittle.

Posted by: DennisV Sep 10 2022, 05:59 PM

Thanks for your reply. Unless I get a better suggestion, I'll do something similar to what I did on our 356 preheat shaft with flaps, which is bead blast and then spray primer then paint with Dupli-Color Engine Enamel. It's not ideal for the rubber or moving parts, but I can't leave it like it is.

Posted by: Mikey914 Sep 10 2022, 06:06 PM

That's what I'd do.

Posted by: bbrock Sep 10 2022, 06:07 PM

I replaced the gaskets on one using some exhaust gasket from the FLAPS and high temperature adhesive. You can't really restore them exactly like original because the gaskets are crimped into the flapper around the edge. But mine have held up and make a good seal.

http://www.914world.com/bbs2/index.php?s=&showtopic=307290&view=findpost&p=2919813, but pretty straight forward.

Posted by: DennisV Sep 10 2022, 06:19 PM

Holy crap! I thought I was obsessive. Nicely done Brent.

I like your initialism

Did you coin that? I hadn't seen it before. Has wide applicability unfortunately.

Posted by: mepstein Sep 10 2022, 07:46 PM

I’ve blasted and powder coated a bunch of them. The air flow isn’t crazy hot and it seems to hold up great. I believe Bruce/bdstone does the same on the ones he restores.

Posted by: bbrock Sep 10 2022, 10:07 PM

Yes, I've noticed you are afflicted with the same disease in your posts.



I forgot about that. As far as I know, that's an original.

Posted by: rgalla9146 Sep 11 2022, 12:35 AM

You heard right, there has been discussion on color of the 914 6 valves but there is no
question that they are originally grey.
I have had some showing plenty of the original paint. Same color as original HEs
I dont have access to pics of them right now.
On the left HE in th picture the original color can be seen.


Attached thumbnail(s)

Posted by: DennisV Sep 11 2022, 06:13 AM

Hmm. From your photo that looks roughly the same as the gray that came on our 356 muffler. It's a very dull. I guess I'd call it flat primer gray. Does that seem like a decent description?

Would love to see more photos if you have them. What I can find via the Google machine, even for 914-6, are black or really poorly lit. Here are the two best I can find that one might call gray:

http://www.914world.com/bbs2/index.php?s=&showtopic=310934&view=findpost&p=2491604

Posted by: rgalla9146 Sep 11 2022, 07:03 AM

Yes, that grey
Stoddard sells it.

Posted by: johnhora Sep 11 2022, 12:59 PM

Years ago before the Stoddard type paint a friend of mine who was a 356 restorer and made 356 mufflers showed me how to use cold galvanizing compound spray paint. His mufflers were on many 356 concours cars.

The prep was to blast the part then spray with cold galvanizing compound spray paint and then take the gas torch to the parts to bake.....I did this on a number of 911 mufflers and headers....worked great and the color was a perfect grey....

The flapper gets very hot since it directs air from the heat exchangers so you need something that can take high heat.

Posted by: mb911 Sep 11 2022, 01:31 PM

Powder would be fine. It melts at of 400 degrees in most cases.

I like the rustoluem high heat gray primer. Works and looks perfect

Posted by: DennisV Sep 11 2022, 03:58 PM

I had hoped that the https://www.duplicolor.com/product/engine-enamel-with-ceramic/ would be a good match. Assuming our 356 muffler is the correct hue, the Dupli-color is a bit too blue.
Muffler in background as purchased from Porsche. Dupli-color primed starter body in foreground.

Posted by: DennisV Sep 12 2022, 06:46 AM

Thanks for sharing @johnhora That is some https://www.rustoleum.com/product-catalog/consumer-brands/stops-rust/cold-galvanizing-compound-spray/. I had not seen it before.

Why did you torch it? I'm reading their spec sheet and is says:


Based on what little I know, I think 200°F would be right at the edge of the engine operating temperature. FWIW - The Dupli-color folks suggest the engine enamel with ceramic will resist temperatures up to 500°F intermittently.

Posted by: johnhora Sep 12 2022, 08:35 AM

Dennis...
that's the way he taught me to do it and he was a true master at his craft....I never questioned him...I just did what he told me to do
It seemed that baked on it made it very durable. Just spraying it on with out the baking it could scratch easier.....and the color came out better baked. I'm trying to see if I have one of the 911 mufflers around. The color is like what you show in you picture above....it's like a white/grey but with out any blue hue. I remember buying VW beetle mufflers years ago from the dealer and they were the same color

Posted by: DennisV Sep 16 2022, 04:02 PM

I got around to glass bead blasting these last night. A couple surprises.

First: I thought under the rust I'd get to at least a chip of original paint. I went from rust to bare metal. Not a trace of paint.

Second: I assume the flapper inside would have a ring of rubber like substance for the seal. Similar to what our 356 had. Instead I found mesh screen. Went easy in the interior areas in the vicinity of that flap. So I don't think I simply blew it away without a trace.


Has anyone had success getting the caps off that are held down by the 4 bent over metal tabs? I would sure like to take them apart for better prep and paint, but it's not worth breaking them.

Posted by: bbrock Sep 16 2022, 06:22 PM

The mesh is what's left of a fiber gasket like your basic exhaust gasket material. I have assumed asbestos given the era they were made. Now you can see how those gaskets were crimped on to the flapper too.

Posted by: DennisV Sep 17 2022, 05:56 AM

Hrm. So maybe even with a light touch the glass bead was too much. My guess is I couldn't tell the rust from the fiber and I unknowingly destroyed it.

Given where we're at, perhaps I should really attack it now with the bead blaster just to try to get any remaining material out of it for safety reasons. At least the media gets filtered in the cabinet and I was wearing a mask when I did it.

I guess the next question is can I salvage these flappers. It looks like @http://www.914world.com/bbs2/index.php?showuser=20845 found a path. Guess there's nothing stoping me from powder coating now if I can get them apart. If anyone has any additional restoration tips or tales of caution, now is the time to share!

Posted by: DennisV May 21 2023, 08:23 AM

Has anyone been successful in disassembling this style of flapper box for repainting and getting it back together without destroying it? Those crimps are really tight.

I don't see how I'll ever get good paint coverage inside while they're together, unless I dip them in something.

Posted by: Aerostatwv May 21 2023, 09:21 AM

I've used the Stoddard paint and it is close to original color. The coverage is awesome so you don't need multiple coats.

Chris

Posted by: DennisV May 21 2023, 10:05 AM

I couldn't find the Stoddard paint available anywhere. I think it was discontinued.

I did http://www.autoatlanta.com/Porsche-Wurth-Zinc-Spray-Paint-13-5-Oz-400ml-Parts-PN-RGR1012.html. I sprayed some out and it is very close color match to our 356 muffler. https://www.wurthusa.com/Chemical-Product/Primers/Zinc-Weld-Thru-Primer-13-53-Fl-Oz/p/0893109 says: - Heat resistant up to 914ºF

I am currently stuck on how to get them apart for painting without destroying them.

Posted by: bdstone914 May 21 2023, 10:46 AM

[Just paint them assembled. I dig out the old seals and blast the inside. I have powder coayed sexeral pairs but it may be overkill.

Posted by: mepstein May 21 2023, 11:04 AM

I don’t take them apart. Just blast and powder coat.

Posted by: 914werke May 21 2023, 11:31 AM

As has been mentioned there is no rubber in them & while their purpose is to route heated air to the cabin, they dont get that hot.
I only powder coat the ones that are in new/great shape with the fiber seal still intact, otherwise ..paint.
Oh & I did try to dissasemble one to see if it was possible to renew seals....once.

Posted by: DennisV May 22 2023, 05:32 PM

When you say "paint", I assume you mean rattle can spray. Did you use special nozzle for that? I am having a hard time seeing how to get paint to the inside flange of the cap for example. The angle just isn't there for a regular rattle can.

I guess there's always spray the bejesus out of it and let it run.

I guess with powder coat, you'd get the benefit of the electronic charge that would draw some paint to unseen areas?

Posted by: 914sgofast2 May 22 2023, 06:51 PM

Someone asked if anyone has straightened the four tabs that hold the mushroom shaped air diffuser on. I did and the tabs are pretty strong. They straightened right out with no problems. I slipped a hose over them to do the factory “fix” for vapor lock on my 1970 model 914.