Can you rebuild a heater flapper box?

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Greg Carter
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Joined: Fri Apr 09, 2010 8:33 pm

Can you rebuild a heater flapper box?

#1 Post by Greg Carter »

I know there are flapper box “rebuild kits” but these only include springs, a few washers and some cotter pins. I’d like to know if it’s possible to rebuild the metal flap hinge pins and the rubber seals on the “valves” themselves.

My flapper boxes have some wear and they don’t operate smoothly because of a lot of slop in the hinge pins of the metal flaps. I think a slightly larger diameter hinge pin would tighten everything up and keep the flap in the right orientation / alignment to operate correctly / smoothly. I’m not sure you can take these apart without splitting welds but thought I’d ask if anybody has a suggestion on how to repair these.

Also, my “valve” rubber is old and brittle and needs to be replaced to seal correctly. I know I need to press the shafts out to weld on my new Precision Matters operating arms but where do I get replacement rubber for the valve while I’m there? I’d read it’s available but didn’t see it at Stoddard or NLA.

Thanks in advance,

Greg

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Rick Albro
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Joined: Thu Mar 27, 2008 12:57 am

Re: Can you rebuild a heater flapper box?

#2 Post by Rick Albro »

Greg,
I think Edwin Schweitzer did a restro-strip on this about 2-3 years ago... I will post the reference when I find it. There are a number of people within the registry that are pretty handy with odd repairs...I would find someone close to where you are to offer guidance as needed. Post a couple pictures of what you are specifically trying to do and I am sure you will get several responses....

the article I was thinking of is https://porsche356registry-production-p ... 1451430996
available under Magazine volume 36 issue 1 from may June of 2012. I guess time gets away from all of us...

Dick Weiss
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Re: Can you rebuild a heater flapper box?

#3 Post by Dick Weiss »

I've rebuilt several flapper boxes needing repair on the shaft pivot holes (adding material to minimize sloppiness) and making & adding sealing pieces w/o disassembling the box. It takes a little work including re-shaping the whole box.

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Steve Hatfield
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Re: Can you rebuild a heater flapper box?

#4 Post by Steve Hatfield »

You can do wonders straightening most of the panels with two sections of 1/4” square key way material available at Ace and a pair of vice grips. Low temp gas-oxy welding is also a handy tool to have to patch any rusted out areas. Powder coating makes a nice finish.
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

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Greg Carter
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Re: Can you rebuild a heater flapper box?

#5 Post by Greg Carter »

Gents,

Thanks for the replys, I appreciate it.

My flapper boxes are straight they’re just worn. The shafts are loose inside the actual flap along with the end caps.

Mr. Weiss, how did you tighten up the pivot pins (hinge pins as I called them)? Do you have a tutorial you might be able to provide?

I’d really like to repair these and avoid spending $1100 on 2 new ones.

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Ron LaDow
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Location: San Francisco

Re: Can you rebuild a heater flapper box?

#6 Post by Ron LaDow »

Greg,
I can help with a technique to make the 'valve' operate properly again, but it is impossible to explain. I'll try to (make the parts) and photo them over the next couple of days.
No help on the rubber sealing 'rings'; someone else is gonna have to pitch in there.
Ron LaDow
www.precisionmatters.biz

Steve Douglas
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Location: Gilroy, CA

Re: Can you rebuild a heater flapper box?

#7 Post by Steve Douglas »

Greg, if you have single flapper boxes then it is way cheaper to buy good ones, I have a set of very nice ones with heat exchangers. Jpipes were repaired with welded on pipe kits. All powder coated gloss black. $250 plus shipping stateside.
Dual flapper boxes would be way more and cheaper to send them to one of the guys who do it regualerly.

Dick Weiss
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Re: Can you rebuild a heater flapper box?

#8 Post by Dick Weiss »

Hello Greg,

I make little L shaped tabs--usually just 1-where the spring tension is pulling the shaft and wearing away the hole.
I add a pop rivet to retain it (after making sure the shaft is straight across and not at an angle) which can't be seen
when installed to the engine. I have a pattern for the seal pieces.

Dick

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Steve Hatfield
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Re: Can you rebuild a heater flapper box?

#9 Post by Steve Hatfield »

I too have a selection of flapper boxes including a pair of the somewhat rare A / pre A single version without carb heat provisions all straight and some with repairs. All either freshly painted or powder coated. I’m also soon to have several 912 version that if not sold as is will be converted to 356 doubles thanks to Ron’s innovative conversion levers.

I’m not flogging here as this is not the place. But I do invite inquiries separately.
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

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Greg Carter
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Re: Can you rebuild a heater flapper box?

#10 Post by Greg Carter »

Mr. Douglas, they are double flappers from my '65C coupe. I appreciate the offer on the single flapper boxes however.

Mr. Hatfield, I already have Mr. Ladow's arms for repairing the boxes I have. I blame him for the slippery slope I have started down :-) Because I already have the arms I had considered buying the cheaper and easier to find 912 boxes and converting a set as you've mentioned. I was hoping to save a few dollars and repair the ones I already have but if that proves impractical then I'll be looking for a set. If you would, can you PM with details for a pair of them?

Mr. Weiss, I'll take any info you have on how you've repaired flapper boxes in the past. What you describe, the spring pulling the flap out of alignment, is exactly the problem I have right now. Along with a loose "valve" shaft as Mr. Ladow talked about. If you could PM or post details on your templates (L bracket and rubber seals) I'd like to try and make the repair parts.

Mr. Ladow, please keep me posted on details for repairing the "valve" shaft. I'm looking forward to seeing how you do it.

EDIT: I just checked the other flapper box (driver side) and, other than the damaged arm I need to replace, it does not have any real wear or slop. I basically need to repair the passenger side box only to solve my issue.

Thanks again.

Greg

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Steve Hatfield
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Re: Can you rebuild a heater flapper box?

#11 Post by Steve Hatfield »

Greg,
I can’t PM you without your contact info. So please email me to open private communications and add your email to your profile,
I’m confident I can help you.
Thanks
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

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Steve Hatfield
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Re: Can you rebuild a heater flapper box?

#12 Post by Steve Hatfield »

Greg,
As luck would have it, I do have an extra 912 double passengers side only needing final coating, paint or pc, buyers choice. 850 259 9759

Email reply sent
Steve Hatfield
Fort Walton Beach, FL
'63 S90 Sunroof Coupe
'06 997S Coupe

Dick Weiss
356 Fan
Posts: 4181
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Re: Can you rebuild a heater flapper box?

#13 Post by Dick Weiss »

Greg,

Using 912 flapper boxes which have the 60mm warm air outlets require a piece of 50mm + section inside the 60mm hose to fit your 50mm entry onto the longitudinal entry tube; Also, it'll need to be longer to loop over the axel tubes,
but R & R-ing the engine is easier when not having the A/B/C flapper boxes w/their "snouts", and adding the upper 1/2 "pull arm" and not needing the tubes for 912 lower pull cables (if they exist) so your cables will connect to the
upper pull holes.

Dick

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Alan Hall
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Location: Orinda, CA

Re: Can you rebuild a heater flapper box?

#14 Post by Alan Hall »

Dick, I think your comments are related to the 912 heater boxes, not the flapper boxes.

Dick Weiss
356 Fan
Posts: 4181
Joined: Sun Apr 20, 2008 12:54 am

Re: Can you rebuild a heater flapper box?

#15 Post by Dick Weiss »

Sorry Alan and all; Getting sleepy for early rise in the morning for the race reunion @ Put-In-Bay, OH this week.

Yup--heat outlet snout/tube is on the heater box including the pull cable tube.

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