73/74 cowl induction Q
Melting Slicks
Joined: Mar 2005
Posts: 2,838
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From: Austin TX
I'm not familiar with this system so I'm afraid all I have is questions.
Am I right in thinking that the flap is a semi sealed (not completely airtight but not bad) so if the air filter housing didn't have the snorkels and the flap failed would it choke the engine?
As carbs designed to run at atmospheric pressure can cause running problems when pressurised, could this be an issue if people are right and the low pressure area at the base of the screen does start to pressurise the air filter area?
Am I right in thinking that the flap is a semi sealed (not completely airtight but not bad) so if the air filter housing didn't have the snorkels and the flap failed would it choke the engine?
As carbs designed to run at atmospheric pressure can cause running problems when pressurised, could this be an issue if people are right and the low pressure area at the base of the screen does start to pressurise the air filter area?
The CI system isn't a Ram-Air system (really no such thing on a carb'd engine). CI simply sources cool fresh air for the carb instead of hot air from the engine bay.
FWIW
Le Mans Master
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St. Jude Donor '14
Team Owner
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From: Ontario
Race Director
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As 7T5 said the flapper is open only at WOT so an alternate path is required at part throttle. Perhaps there was an initial design to block the snorkels at WOT but who knows. I'm still not totally convinced that the duct is sufficiently large in size to properly feed the engine but that starts a whole new discussion.
Team Owner
Joined: Aug 1999
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From: Ontario
I'm not at all sure why the OEM did what they did. I'm sure they would be killing themselves laughing at us trying to reverse engineer it 37 years later........
As 7T5 said the flapper is open only at WOT so an alternate path is required at part throttle. Perhaps there was an initial design to block the snorkels at WOT but who knows. I'm still not totally convinced that the duct is sufficiently large in size to properly feed the engine but that starts a whole new discussion.
As 7T5 said the flapper is open only at WOT so an alternate path is required at part throttle. Perhaps there was an initial design to block the snorkels at WOT but who knows. I'm still not totally convinced that the duct is sufficiently large in size to properly feed the engine but that starts a whole new discussion.
Pro
Joined: May 2003
Posts: 593
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From: London England
Ahh thanks for the pics Paul, that makes more sense now.
I don't know why but I assumed the flap was vacuum operated, not on a solenoid. I was thinking it was more progressive dependant on engine load but is clearly either on or off.
Regarding the intake area in the hood, I suspect if you did the math that's actually quite a reasonable sized area
I don't know why but I assumed the flap was vacuum operated, not on a solenoid. I was thinking it was more progressive dependant on engine load but is clearly either on or off.
Regarding the intake area in the hood, I suspect if you did the math that's actually quite a reasonable sized area
Team Owner
Joined: Aug 1999
Posts: 30,995
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From: Ontario
Ahh thanks for the pics Paul, that makes more sense now.
I don't know why but I assumed the flap was vacuum operated, not on a solenoid. I was thinking it was more progressive dependant on engine load but is clearly either on or off.
Regarding the intake area in the hood, I suspect if you did the math that's actually quite a reasonable sized area
I don't know why but I assumed the flap was vacuum operated, not on a solenoid. I was thinking it was more progressive dependant on engine load but is clearly either on or off.
Regarding the intake area in the hood, I suspect if you did the math that's actually quite a reasonable sized area
On my 1974 both the cowl induction setup and the kickdown on the TH400 transmission is electrically triggered by a switch (adjustable) on the gas pedal, roughly coinciding with a WOT condition. I do not have a kickdown cable on the carb. Bit of an odd system??
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Pro
Joined: May 2003
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From: London England
It is unusual on a car of that age to have electronic kick down, lots of manufacturers used a rod or vacuum unit right up until the late 80's.
I wonder how hard it would be to use a vacuum unit to open the flap so it could open with load rather than throttle position
Another good pic BTW
I wonder how hard it would be to use a vacuum unit to open the flap so it could open with load rather than throttle position
Another good pic BTW
Race Director
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It could have also been linked in with the choke ***'y to use underhood heat only to help warm the carb then use solenoids to simultaneously open the flap and close the snorkels at WOT but again, we're 37 years too late to ask the right people 'why'.
when it opens!
Team Owner
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From: Ontario
Melting Slicks
Joined: Mar 2005
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From: Austin TX
Correct, the hood flapper is either open or closed.
One trick we Camaro guys do, is fit a 1" length of fuel hose over the actuating rod on the switch at the pedal. This will activate the flapper sooner (and more often) and for longer periods of time.
Seems the fuel hose size needed was 5/16" but may have been 3/8". One of those fits perfectly.
FWIW
One trick we Camaro guys do, is fit a 1" length of fuel hose over the actuating rod on the switch at the pedal. This will activate the flapper sooner (and more often) and for longer periods of time.
Seems the fuel hose size needed was 5/16" but may have been 3/8". One of those fits perfectly.
FWIW
Last edited by 73, Dark Blue 454; Jan 12, 2010 at 03:45 PM.
Racer
Joined: Sep 2011
Posts: 408
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From: Ormond Beach Florida
82' cold air cowl intake flapper
I have been reading the arguments concerning the cold air cowl intake for the past 20 minutes and have enjoyed the varied opinions of the "engineers." I have one questions, Should I remove my colde air cowl intake flapper from my 1982 (crossfire) or spend the overpriced money to replace existing (with deteriorated foam cushioning). I am not an engineer, but common sense tells me that more air (and cooler air at that) would enable an engine to breath better (how much better is the debate).
Thank all of you guys anyway. I have learned a lot from the forum since my restoration project has started earlier this month.
Thank all of you guys anyway. I have learned a lot from the forum since my restoration project has started earlier this month.
Le Mans Master
Joined: May 2007
Posts: 5,021
Likes: 1,120
From: North tonawanda NY
I have been reading the arguments concerning the cold air cowl intake for the past 20 minutes and have enjoyed the varied opinions of the "engineers." I have one questions, Should I remove my colde air cowl intake flapper from my 1982 (crossfire) or spend the overpriced money to replace existing (with deteriorated foam cushioning). I am not an engineer, but common sense tells me that more air (and cooler air at that) would enable an engine to breath better (how much better is the debate).
Thank all of you guys anyway. I have learned a lot from the forum since my restoration project has started earlier this month.
Thank all of you guys anyway. I have learned a lot from the forum since my restoration project has started earlier this month.
This would effect those driving in colder temps more than the summer cruisers I think.
All the CI stuff was long gone on my 74 when I bought it primerily because of the greenwood hood. I may consider using a CAI like the spectre which has two hoses I can route to the now mainly non functional side vents.
Same for my 1973.
Le Mans Master
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2022 C3 of the Year Finalist - Modified
77 Cold Air Induction
On the same note, is the 77 and up style of cold air induction a significant improvement over an open air filter as in the early models? I get the idea, but wonder what the real improvement. Is it strictly a high RPM full throttle type of thing that adds a few HP? I have seen these obnoxious cold air inductions that someone is selling here on the Forum, and they obviously believe there is some valuable reason to clutter up underhood appearance.
I personally won't even have airconditioning in the car simply because of the excessive crap under the hoodl For me, I want to see the engine the way it was in the 60;s. Anyway??
I personally won't even have airconditioning in the car simply because of the excessive crap under the hoodl For me, I want to see the engine the way it was in the 60;s. Anyway??
