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> Heater Flappers for 914-6
Biggles
post May 31 2017, 02:03 PM
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Hi all

apparently there is a difference between a 4 and 6 cylinder cars' heater flapper boxes, but can't immediately tell what the difference is. Would a -4 work on a -6 ? I have a 3.2 engine and want to add heat exchangers

cheers.
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Luke M
post May 31 2017, 03:37 PM
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The 4 doesn't have a hole on the cap where the 6 does.
See the pic. It's a 6 flapper box. I believe the hole is there to get rid of more heat/air from the heater boxes.


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914Next
post May 31 2017, 07:06 PM
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QUOTE(Luke M @ May 31 2017, 05:37 PM) *

The 4 doesn't have a hole on the cap where the 6 does.
See the pic. It's a 6 flapper box. I believe the hole is there to get rid of more heat/air from the heater boxes.



huh....always learning something hanging around here.
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rgalla9146
post May 31 2017, 08:30 PM
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All 914 6 flappers that I've seen are grey.
4 cyl. are black
The valves will mount on the 6 heat exchangers
The answer to your question depends on the position of the arms that operate the valves.
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Biggles
post Jun 1 2017, 01:33 AM
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So apart from a hole and paint colour, is there any other difference?

Are the arm positions different? Look similar to me. What about pipe diameter? Can someone advise on OD diameter between the two please?

6 ones go for big $$$ and I can't see why -4 ones can't be made to fit.
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IAA1963
post Jun 1 2017, 03:33 AM
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Yes, the pipe diameter below the cap is different. But that is all I have noted.
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Biggles
post Jun 2 2017, 03:41 PM
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QUOTE(IAA1963 @ Jun 1 2017, 10:33 AM) *

Yes, the pipe diameter below the cap is different. But that is all I have noted.


interesting as I note in an old Pelican post that a 4 flapper will work on the 6 car

http://forums.pelicanparts.com/porsche-914...pper-boxes.html
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pete000
post Jun 2 2017, 04:08 PM
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QUOTE(Luke M @ May 31 2017, 01:37 PM) *

The 4 doesn't have a hole on the cap where the 6 does.
See the pic. It's a 6 flapper box. I believe the hole is there to get rid of more heat/air from the heater boxes.


I did not know that !

My six has the non hole 4 flapper boxes and they fit and work just fine.
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JmuRiz
post Jun 6 2017, 07:57 AM
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Phew...glad the /4 parts work for a 914/6 conversion with heat!
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gereed75
post Jun 6 2017, 09:59 AM
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Running 4's on my six. They work normally. Thinking about opening holes on them similar to the six ones. Holes are there for a reason and I suspect that they flow some heat away from the exchangers/headers when the flapper is closed.

Good idea??
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GeorgeRud
post Jun 6 2017, 11:51 AM
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I also have used the -4 flapper boxes on my -6 conversion successfully, but now plan to drill the caps on the flapper boxes to increase the flow through the flapper boxes when the heat is closed off. I figure Porsche must have had a reason to design the -6 flapper boxes with a hole in the cap.
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914Sixer
post Jun 6 2017, 02:41 PM
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Get your hole saw out and make ANY -4 box into to a -6 box.
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johnhora
post Jun 6 2017, 03:14 PM
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Do a search on this ....been talked about before by some of our knowledgeable experts...the 6 has the flapper with a hole in it like in Luke's post....apparently this is so more air runs thru the HEs to help keep the engine cool when closed...with out it the engine over heats....
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Biggles
post Jun 7 2017, 07:51 AM
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QUOTE(GeorgeRud @ Jun 6 2017, 06:51 PM) *

I also have used the -4 flapper boxes on my -6 conversion successfully, but now plan to drill the caps on the flapper boxes to increase the flow through the flapper boxes when the heat is closed off. I figure Porsche must have had a reason to design the -6 flapper boxes with a hole in the cap.


that's what i'll do with mine - being Porsche, they did these things for a reason !
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gereed75
post Jun 27 2017, 06:55 AM
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Ok guys, we were wrong on this one.

Was mounting my 4 flapper valves and decided to add the six holes. Put in some holes and then decided to get my six flappers out to see how big the holes are supposed to be. While looking into the hole on the four flappers I noticed cutouts in the internal tube under the "mushroom" cap (they look like the cutouts on top of a castle tower). Then I looked at the six ones to compare. The castellated cutouts on the four version are twice the size as on the six version.

So it looks like the four version passes just as much air through these larger vents as the six version does through the smaller vents and the hole.

Maybe the engineers did this as a slight cost savings. While cutting the vents in the tube, might as well make them bigger and skip the extra step of adding the hole?

So now I have double venting flappers. Makes me wonder if I am robbing some air that would otherwise flow through the shroud to the cylinder fins? Oh the horror!
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IAA1963
post Jun 27 2017, 02:20 PM
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Some pics of the different tube diameters of the /4 and /6 heater flappers ...

The one on the left is a /4 flapper box. The one in the middle a sandblasted unit from my original /6 and a new /6 flapper box on the right.

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Steve
post Jun 27 2017, 02:55 PM
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Interesting... I have been running 4 banger ones with factory heat exchangers for 20 years with no problems. I just upgraded to mb911 heat exchangers and they still work fine.
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Biggles
post Jun 27 2017, 03:15 PM
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cheers for posting - useful to know. I was going to adapt the ones I've bought, but seems like no need

QUOTE(gereed75 @ Jun 27 2017, 01:55 PM) *

Ok guys, we were wrong on this one.

Was mounting my 4 flapper valves and decided to add the six holes. Put in some holes and then decided to get my six flappers out to see how big the holes are supposed to be. While looking into the hole on the four flappers I noticed cutouts in the internal tube under the "mushroom" cap (they look like the cutouts on top of a castle tower). Then I looked at the six ones to compare. The castellated cutouts on the four version are twice the size as on the six version.

So it looks like the four version passes just as much air through these larger vents as the six version does through the smaller vents and the hole.

Maybe the engineers did this as a slight cost savings. While cutting the vents in the tube, might as well make them bigger and skip the extra step of adding the hole?

So now I have double venting flappers. Makes me wonder if I am robbing some air that would otherwise flow through the shroud to the cylinder fins? Oh the horror!
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gereed75
post Jun 27 2017, 04:58 PM
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The diameters measured by IAA1963 are the diameters of the inner tubes. These do not effect fitment. Mount diameters appear to be the same.

Note the depth of the castlellated cutouts. The four cutouts are almost twice as deep as the six

Not sure I could disassemble my six flappers like this as the tabs appear to be welded. Maybe not, I'll check later
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IAA1963
post Jun 27 2017, 11:20 PM
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The taps on the /6 flappers are not welded. The cover is quit easy to remove.

But the cover on the /4 flapper was welded and is difficult to remove. The second flapper of my /6 was damaged too much, so I wanted to mount the cover with the hole of my /6 to a NOS /4 flapper. But after removing the welded spots on the /4 flapper I have figured out that it does not fit due to the different tube diameters.

Meanwhile I have a second grey NOS flapper to complete my set.
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