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Will repro Ram Air flappers work with OEM plenum
#1
I have a original Ram Air plenum but the flappers/actuator encasements are missing. I was wondering if i bought the repro if I can use those pieces. I know they use to sell them separate but I cant find them anymore.
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#2
I don't have the Ram Air optoin on my Mustang but I am curious. I see it is vacuum driven. What is the vacuum source? Does the manifold vacuum actually 'close' the flappers and they open under load (low manifold vacuum)

'Mike'
73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

Pics of modifications included in:
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#3
Yes, you can hear them close when you shut off the motor
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#4
CZ-75;166326 Wrote:Yes, you can hear them close when you shut off the motor

Oh, I get it. You are saying that stopped and in park (maximum manifold vacuum) the manifold vacuum is holding them 'closed'. When there is no vacuum (under load) there is a spring or something that opens them.

Cool.

'Mike'
73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

Pics of modifications included in:
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#5
Yes, the high manifold vacuum holds the flappers closed under normal driving. Full thottle causes very low manifold vacuum, allowing the flappers to open...conveniently, just when you need it. Simple and elegant system.
Yes, the repro flappers will fit perfectly on an OEM plenum.
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#6
Kit Sullivan;166330 Wrote:Yes, the high manifold vacuum holds the flappers closed under normal driving. Full thottle causes very low manifold vacuum, allowing the flappers to open...conveniently, just when you need it. Simple and elegant system.
Yes, the repro flappers will fit perfectly on an OEM plenum.
Kit,
Good to hear. Funny thing about my current ones. The cases that i have where the flippers would go don't look like they ever had flippers. Nor do I see holes where the actuators would go. Did they make some ram air without flippers?
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#7
I thought default position was open.
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#8
jeremycfr;166336 Wrote:I thought default position was open.


Nope - unless you identify 'default' as being condition where engine is off (zero relative manifold vacuum). Mine have always worked just as Kit described.

Ray

1971 Boss 351  
1972 Q code 4 speed convertible 
1971 Mustang Sportsroof  351-2V FMX 
1971 Hardtop (parts car)
1973 Mach 1 (parts car)
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#9
"Default" position with egine off is flappers open. Manifold vacuum at idle closes them so you can drive under normal conditions without ingesting water or other unwanted contaminants into your intake system.
I believe the assumption by Ford is that the only time you would operate the car under full throttle would be in dry weather, precluding any unwanted stuff from getting in your engine.

The flapper scoops you describe sound like the aftermarket repros sold by Leon at "fordramair.com". He made them without an actual working flapper for simplicity and to keep costs down. They are open full-time, so water-ingestion is a possibility in heavy rain driving.
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