Non Return flap- am I missing something?

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highlandmurf
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Non Return flap- am I missing something?

Post by highlandmurf » Wed Mar 20, 2013 10:12 am

I am missing the passenger side non return flap, but there is no place to attach one.

See, no holes for the little wire pin:

Image

So, Did all of the fan shrouds have a passenger side flap?

Does this look like it has been modified?

Should I worry about not having one?

Thanks
'76 Westy Marino Yellow

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Amskeptic
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Re: Non Return flap- am I missing something?

Post by Amskeptic » Wed Mar 20, 2013 10:55 am

highlandmurf wrote:I am missing the passenger side non return flap, but there is no hole for the little wire pin:

So, Did all of the fan shrouds have a passenger side flap?
Does this look like it has been modified?
Should I worry about not having one?
Yes, yes, yes, m'boy.

If you don't mind a little inefficiency in your heat, don't worry about it. BUT, you must have functional flaps in the heater blower housing.
Colin
BobD - 1978 Bus . . . . . . . . . . . 112,660 miles
Chloe - 1970 bus . . . . . . . . . . . 206,845 miles
Naranja - 1977 Westfalia . . . . . 112,885 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,899 miles

CarlosZ
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Re: Non Return flap- am I missing something?

Post by CarlosZ » Mon Feb 20, 2017 2:55 pm

I've no heating parts, only a header to muffler. Are the two non-return flaps needed? If so, should they remain flapping open or closed off somehow? I'm under the assumption that closing them does change the air flow. I think by closing them off you get turbulence or disrupted airflow within the shroud, but more air volume/flow overall or sufficient air to keep it cool. Isn't there is a great loss of air pressure/volume/flow to the heads due to having so much air escape through the openings at the bottom of the shroud if removed or left to flap open? The heating system must have restricted the volume of flow (from the shroud exit) greater than leaving off or leaving them flapping. Keep getting conflicting advice. Just want as many opinions so I can make an educated decision. Thanks!

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Bleyseng
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Re: Non Return flap- am I missing something?

Post by Bleyseng » Tue Feb 21, 2017 10:36 am

On race engines they still leave em open and they run headers....
Geoff
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
76 914 2.1L-Nepal Orange- 160,000+ miles
http://bleysengaway.blogspot.com/

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Amskeptic
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Re: Non Return flap- am I missing something?

Post by Amskeptic » Thu Feb 23, 2017 8:49 am

CarlosZ wrote: I think by closing them off you get turbulence or disrupted airflow within the shroud,
loss of air pressure/volume/flow to the heads due to having so much air escape through the openings at the bottom of the shroud if removed.
I'd experiment. Got CHT gauge? Run them open, read gauge at specified control speed load.
Then tape them off. Read gauge at specified control speed load.
Report back.
Colin
(specified control speed load: 60 mph for 15 miles in one direction then 15 miles back, tape then repeat)
BobD - 1978 Bus . . . . . . . . . . . 112,660 miles
Chloe - 1970 bus . . . . . . . . . . . 206,845 miles
Naranja - 1977 Westfalia . . . . . 112,885 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,899 miles

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