Double flapper boxes - how closed is closed?

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James Fitzsimons
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Double flapper boxes - how closed is closed?

#1 Post by James Fitzsimons »

Hi all,

I've spent considerable effort getting my flapper boxes back into shape - there were completely non-functional when I purchased my car years ago. However, now I am at finally assembly stage I can't quite get them to work correctly. They close with a snap, but they will not open again using the front lever, I have to pull the back flapper open about an inch before the lever will finish opening them up.

Looking at the leverage point it seems unlikely that the lever will be able to open them as the point the long rod connects to the back flapper is so high and close to the pivot point it has almost no leverage to overcome the spring tension holding it closed.

Are the flaps supposed to be fully closed when the front lever is in the open position?

Here's what my boxes look like with the front lever in the open position and the flaps fully closed.
PXL_20220918_054052199.jpg
PXL_20220918_054036860.MP.jpg
Any advice you can provide is much appreciated!
James Fitzsimons
1957 356A Coupe (RHD)

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Bill Lawless
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Re: Double flapper boxes - how closed is closed?

#2 Post by Bill Lawless »

Not an answer to your question,,, But
What timing, I was going to work on mine today... I also have the same problem won't fully close or open... I like to drive in the Fall with the top down and the heat on..
 Thanks,
Bill
65' 356 SC Cab Irish Green :D
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Martin Benade
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Re: Double flapper boxes - how closed is closed?

#3 Post by Martin Benade »

The rod connector pieces on the flaps are curved a bit such that they can be bent to adjust. I think you can improve the leverage if you study which way to bend them. I did a pair two months ago, and that was part of getting them working.
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Mike Wilson
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Re: Double flapper boxes - how closed is closed?

#4 Post by Mike Wilson »

Also make sure the cables are adjusted correctly at the heater boxes and the flaps aren't binding on the bodies of the boxes.

Mike
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John Brooks
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Re: Double flapper boxes - how closed is closed?

#5 Post by John Brooks »

Look closely at the rod clamps one is shorter and has a single nut. They go on the upper portion of the pivot lever on the rod, the longer ones with 2 nuts go on the cables . I adjust the heater to full hot by the shifter. Then close the heater box flap by hand before I attach the cable, then adjust the rod and the shut off valves to full open. Don’t forget the plastic tube covers on the cables, or you get to start over.
Then full cold to insure the louvers open completely, then back to full hot and do some final tweaking on the cable and rod to insure they are opening and closing as designed. Making sure the valves are full close when the heater box is open keeps the interior cooler in the summertime.
John Brooks

62 Roadster
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getting pushed around in porsches since 1965

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Martin Benade
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Re: Double flapper boxes - how closed is closed?

#6 Post by Martin Benade »

He’s having trouble with the internal rod adjustment, done by bending things. Once that’s working then the cable and clamped in rods can be adjusted but the flappers need to be functional first.
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Dick Weiss
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Re: Double flapper boxes - how closed is closed?

#7 Post by Dick Weiss »

A little clarification;

The J-pipes have the heater boxes or considered as heat exchangers.
The single or double flapper boxes have the pivot arms to close the forward valve for cooling
or open for heat. I consider them as lower air guides and the forward heat control valves
must be connected w/their long forward rods back to the lower hole in the pivot arms.

As mentioned, the flaps must be free from rubbing the walls of the flappers--Remember, the spring
on the pivot arms must be connected correctly to return the 'flappers' to open (lever forward or
the knob turned clockwise) when heat isn't needed.

All the above is shown in the shop manual or recently in the technical section of the Registry.

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James Fitzsimons
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Re: Double flapper boxes - how closed is closed?

#8 Post by James Fitzsimons »

Thanks everyone for your replies.

I have double checked the flaps aren't rubbing / binding on the walls. I am now trying to adjust the flaps by bending the tabs that the rods fit into. It's pretty frustrating but I think I am closing in on the solution.

Just to confirm though - the flaps should be completely closed when the forward (lever) valve is fully open, and the flaps should be fully open (as far as they can) when the forward (lever) valve is fully closed?

I have hunted through the 'C' workshop manual and in the technical section of the registry site, but the only information I could find was for the single flapper boxes.

Many thanks and regards
James Fitzsimons
1957 356A Coupe (RHD)

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Martin Benade
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Re: Double flapper boxes - how closed is closed?

#9 Post by Martin Benade »

You are correct on where the levers and flaps need to be, keep fine tuning.
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Bill Lawless
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Re: Double flapper boxes - how closed is closed?

#10 Post by Bill Lawless »

I have a question on this also, If you are not using the Thermostat controlled Carb warm up flaps is there a way to plug the hole so you don't loose heat there..
 Thanks,
Bill
65' 356 SC Cab Irish Green :D
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81 VW Westfalia with 2015 Forester Engine
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James Rowe
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Re: Double flapper boxes - how closed is closed?

#11 Post by James Rowe »

On VW’s when we wanted to block them off, we got Freeze plugs from the auto parts stores that were the same size. They also made rubber expandable ones, you may try that as well.
Bill Lawless wrote: Mon Sep 19, 2022 8:32 am I have a question on this also, If you are not using the Thermostat controlled Carb warm up flaps is there a way to plug the hole so you don't loose heat there..
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You just need to find the correct size.
You just need to find the correct size.

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Martin Benade
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Re: Double flapper boxes - how closed is closed?

#12 Post by Martin Benade »

A freeze plug that’s a bit too big, upside down with silicone sealant is about the easiest way.
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Bill Lawless
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Re: Double flapper boxes - how closed is closed?

#13 Post by Bill Lawless »

Is the heat an issue with the rubber plug?
 Thanks,
Bill
65' 356 SC Cab Irish Green :D
82' SC Targa
81 VW Westfalia with 2015 Forester Engine
BMW 64'-R50/2, 75'-BMW R90/6, 74' BMW R90/6, Yamaha BW350

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Martin Benade
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Re: Double flapper boxes - how closed is closed?

#14 Post by Martin Benade »

It doesn’t get that hot, it should be fine.
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Dick Weiss
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Re: Double flapper boxes - how closed is closed?

#15 Post by Dick Weiss »

If you do some driving in cold weather, the thermostat will adjust the crossbar to allow some heat
to prevent the carbs from getting "frosty". Otherwise, the adjustment of the linkage could keep
the crossbar (w/its flaps) closed preventing heat to the carbs--and still using the lower tubes
and upper snouts to give the correct look in the engine compartment.

Other owners just close the holes in the rear cover/plate w/a flat plate w/3-screws, but some heat
will continue flowing underneath due to not using the lower tubes.

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