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914World.com _ 914World Garage _ Heater Flappers for 914-6
Posted by: Biggles May 31 2017, 02:03 PM
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. 
Posted by: Luke M May 31 2017, 03:37 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.
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Posted by: 914Next May 31 2017, 07:06 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.
Posted by: rgalla9146 May 31 2017, 08:30 PM
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.
Posted by: Biggles Jun 1 2017, 01:33 AM
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.
Posted by: IAA1963 Jun 1 2017, 03:33 AM
Yes, the pipe diameter below the cap is different. But that is all I have noted.
Posted by: Biggles Jun 2 2017, 03:41 PM
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-914-914-6-technical-forum/257254-914-6-heater-flapper-boxes.html
Posted by: pete000 Jun 2 2017, 04:08 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.
Posted by: JmuRiz Jun 6 2017, 07:57 AM
Phew...glad the /4 parts work for a 914/6 conversion with heat!
Posted by: gereed75 Jun 6 2017, 09:59 AM
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??
Posted by: GeorgeRud Jun 6 2017, 11:51 AM
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.
Posted by: 914Sixer Jun 6 2017, 02:41 PM
Get your hole saw out and make ANY -4 box into to a -6 box.
Posted by: johnhora Jun 6 2017, 03:14 PM
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....
Posted by: Biggles Jun 7 2017, 07:51 AM
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 !
Posted by: gereed75 Jun 27 2017, 06:55 AM
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!
Posted by: IAA1963 Jun 27 2017, 02:20 PM
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.
Posted by: Steve Jun 27 2017, 02:55 PM
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.
Posted by: Biggles Jun 27 2017, 03:15 PM
cheers for posting - useful to know. I was going to adapt the ones I've bought, but seems like no need
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!
Posted by: gereed75 Jun 27 2017, 04:58 PM
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
Posted by: IAA1963 Jun 27 2017, 11:20 PM
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.
Posted by: Steve Jun 28 2017, 07:15 AM
Curious if it's just a VW parts bin versus Porsche parts bin thing or is there a technical reason of one over the other? Do the concours judges look for this?
Posted by: bdstone914 Jun 28 2017, 08:24 AM
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!
The purpose of the vent holes is to prevent a high temperature build up of trapped air in the heat exchangers that would be sent to the cabin when the flappers are first opened. I doubt you are losing any significat amount of cooling air to the cylinders with added venting.
Discussed this with Wayne Dempsey recently.
Bruce
Posted by: IAA1963 Jun 28 2017, 04:10 PM
The /4 flapper box I have is a Porsche part, too. Not VW part.
Posted by: Steve Jun 28 2017, 07:12 PM
It has a VW part number sourced from Volkswagen, but probably marked up since it has a Porsche sticker on it.
http://www.aircooled.net/vw-part-numbers-explained/
Posted by: bdstone914 Jun 28 2017, 07:47 PM
It has a VW part number sourced from Volkswagen, but probably marked up since it has a Porsche sticker on it.
http://www.aircooled.net/vw-part-numbers-explained/
I believe the VW Bus and 914 flapper boxes differ on the clocking of the lever. Amoung the crate of flappers I have there are at least four variations on the lever clocking.
Bruce
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Posted by: Steve Jun 28 2017, 09:37 PM
Thanks Bruce!! Learn something new every day. I didn't know there was 914 specific VW part numbers. I heard stories about how some of the parts are interchangeable with VW, such as the window winders. Assumed that included the flapper boxes.
Posted by: Mark Henry Jun 29 2017, 06:24 AM
If you have the fuel pump in the stock location, I'd take the cap off the right valve and run a Beetle pre-heat hose over and away from the pump.
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