Thanks, that's the correct quote.

 

The point is the comment was on BB weight 396 /427 & indicates how he got the 427 in the Vette instead of the 396.

 

From MW: "I've recieved great photos of both the ZL2 and plenum induction systems which demonstrates why one works and the other doesn't. The Camaro guys are having a good laugh at you guys going over ground that they beat to death almost 40 years ago."

First, as a full fledged Camaro guy (currently own 3 first gens and early member of www.camaros.net) I can assure you, nobody laughs at cold air induction designed for Vettes.

Plus, one could argue that the Vette Cowl Induction syetem would be more effective than Camaro since the underhood (snorkel) temps (and cabin temps BTW) of a Vette are much higher than a Camaro, making cold air induction more effective, and more needed.

Secondly, I'm the only one providing docs or photos to this point, and I've yet to see to your response to this:

http://s421.photobucket.com/albums/p...=YarnTest2.jpg

It's a simple test with five 6-8" lengths of yarn taped to the back of the cowl hood of a 74 Vette traveling 40 mph.

 

Like I said in post #3 to answer the OP.
I taped up the 2 snorkels with A/C foil tape and removed the flapper and solenoid.

The ONLY intake air I get is colder and 100% from the cowl induction, whether at 0mph or 110mph, and yes 30 years ago, in a frozen climate, it would instantly suck in a layer of fresh powder snow instead of yarn at startup.

 

Let me throw this in...
If the snorkels were blocked off all the time, wouldn't the cowl opening always draw air, even at 0 mph? The carb has to breathe air from somewhere.

I'm going to get some yarn. Of course I may have to drape them over the edge, to begin with, so they can find their direction into the air stream.

PS: Not a good idea for those that live above the frost line.

 

Big Eddie,..the thinking is, that if the cold air doesn't vent back out of the snorkels, the awaiting air will heat up.

From here;

http://www.camaro-untoldsecrets.com/...es/rpo_zl2.htm

...is this:

"The smallish, single snorkle exiting the passenger side (Vettes have two snorkles) of the air cleaner provided underhood air to the carburetor during normal driving. When the throttle was opened fully (over 90%) fresh, cold air from the cowl area flooded the air cleaner assembly."

The cold air has to replace itself and needs somewhere to vent, otherwise it would be like blowing into a sheetmetal baloon. At some point, you can blow no more air, cold or otherwise. You need a vent for the air cleaner which is the function of the snorkel when the throttle "goes loud" and the flapper is opened.

To test this, lay a 6-8" length of yarn in the snorkle, taped at the end of the snorkle (wrap a piece of tape around the outside of the end of the snorkle). Take your 73-75 Vette for a spirited drive.

Then report back the reason why you believe the yarn is now outside of the snorkel.

 

Your point is understood, but....

Ole Blue, I'm thinking if my motor is running and the snorkels are blocked off, the air won't take long to vent itself down thru the carburetor and out the exhaust. Hot or cold! I always drive spirited.

My point was, forget the snorkel vents by blocking them off all the time and run with the cowl induction 100% of the time as was mentioned by some. Fresh air entering the air cleaner 100% of time won't have time to get hot except maybe when you're sitting still, and that won't be for long in my case. I'm always on the move and my cold air ain't waitin' on nothing!

Since the hood is insulated to an extent, the engine is running and fresh air is moving in only thru the cowl vent, how can it get hot even at idle? I'm still gittin' the yarn and it's only going to be on the outside!
I can draw ya a picture.

 

Just takes a couple moments, no big deal.

 

How does your air cleaner housing seal against the hood? Did you remove the seal to take the pic?

 

Everything else is the stock cowl induction setup, extension ring, and rubber seal.
The cowl flapper door and the solenoid that operates it were removed and the housing on the hood was reinstalled, so it is identical to the original setup, just open all the time.

 

OK, I just couldn't see where the extension ring had been touching the base.

 

Solid,
G'day, long time no speak , this is an interesting thread, as I have a '74 L82, but don't have any of the C.I. air cleaner parts. The car came with a real cheap, probably Chinese, open side air cleaner when I bought it. Although I found the cowl switch on the accelerator pedal, there was no wiring attached to it. I've since replaced the wiring from the switch to the solenoid, and it works when the throttle is floored, but still have to find all of the stuff that bolts onto the carburettor - the flange, rubber seal etc.

I've often wondered about the effectiveness of the C.I., but after reading all of the above, I am inclined to agree with my fellow Commonwealth member that any gains that it makes are immeasurable.

However, as the ambient temperatures in Melbourne range from 0 degrees C (albeit very rarely!) in winter to over 40 ( very often! ) in summer, and we never see snow, I prefer to have the coldest air possible flowing into my carburettor all year round. Therefore, I will acquire the parts needed and put them in place. I will more than likely block off the two snorkels as well, but will await eagerly noonie's testing in this area.

Keep it coming.

Regards from Down Under

aussiejohn

 

I finally got a chance to get some measurements with my cowl induction setup.
It was a chilly day here.

Engine uses a 195° thermostat.
The rear of the hood still has a well worn cowl seal.
The air cleaner to hood cowl seal is old and also worn.
There are no core support seals.
The 2 front snorkels are blocked off.
The flapper and solenoid are removed.
The engine sees only the air from the windshield base at all times.
A fairly accurate pyrometer was used.


Ambient temp........68°



Temp at air filter inside air cleaner assembly.
At 70 mph ........68.6°
At stop and go aprrox 35 mph .......68.9°
At prolonged idle........70.8°



Temp at opening to one snorkel in engine compartment (remember snorkel is blocked off, but this is in air the path)
At 70 mph.......137.2°
At 30 mph.......131.6°
At prolonged idle.......157.7°
I would assume, with core support seals the underhood temps would be higher.

Clearly at 70 mph there is approx 69° difference

Most often the ambient temps are 95+° here and the underhood temps much higher also.

It's clear that this setup draws ambient air just as almost all cars do over the last 25 years and I assume all car makers had good reason.
I will let others debate the horsepower issue, but it seems that there may be some merit.

And to answer the OP, it has been this way for a couple years with no downside I have discovered and there seems to be no need to extend the front snorkels, just block them off.

 

That's the info I'm after, the engine is drawing enough cold air in to make a difference.
What happens if you pipe the two front ones down some where colder than the engine bay, I've got to think that would help as well.

Jerome

 

All those numbers make perfect sense Noonie. Thanks for doing the test

Ahh, you said chilly day- but 68* sounds pretty good to me right now.

I'll repeat my own test in the spring for consistency sake, then block off the snorkels like your setup to see if our numbers correlate.

 

Nice work Noonie.

The engineers tell us that for every 11 degrees F intake temperatures are reduced, there's a 1% increase in HP.

So with the 69 degree reduction in intake temperature, provided by the cowl induction system, you would realize a nice HP gain.

 

(quote)"I'll quote all degrees in F as I know very few of the Luddites here understand degrees Celsius."




So Mike if you dont insult anyone whats this??? So its ok for you to,but If we give you back what youve dished out its not ok....WTF...


I think that GM woulnt have kept COWL INDUCTION If it had no affect at all on performance. Granted it was more affective as a selling point than performance.

 

I think you mean 'effective'. They didn't keep it. It got ditched in '76.

How's your L82 BTW?

 

Not to mention the money they could have saved on the L88 option !

 

[QUOTE=Mike Ward;1572691047]I think you mean 'effective'. They didn't keep it. It got ditched in '76.

How's your L82 BTW?

Ill tell you this, Its best your in Canada. Wouldnt do you any good to be the southern states. BS like yours gets delt with.

Love to meet you at a show some time...