[KevinW]

Comparision of ZL2 "Cowl Induction" air cleaners

The ZL2 cowl hood for 69 Camaros was developed for racing, but was introduced mid December to go on COPO 427s and then went to SS and Z/28 Camaros. The ZL2 hood was also called the "super scoop" by the advertising group. That name went out of style when the 70 Chevelle was introduced with it's "cowl induction" hood. This name stuck for Camaros too.

A lot of Camaro owners who are restoring their cars or adding the ZL2 "Cowl Induction" hood ask "How do I recognize an original air cleaner?" We will compare 3 types of air cleaners and mark the differences. We will compare an original automatic trans air cleaner from a 69 Pace car, a manual trans repro cleaner and a 70 Chevelle manual trans cleaner.

Group shot

They look pretty similar, Huh?
Notice the vacuum valve on the original's snout. This was only used on the automatic cars to draw heated air from the heat riser. Manual trans cars did not have the valve. All 69 air cleaners for automatics, 2 or 4bbls, had the same snout. Great Donor part!

Original

Notice the flat bottom where the filter rests and the forming wrinkles in the metal.
Also notice the small air valve in the center. This sensor is for the snout valve, only on automatics.

Repro

Notice the ridge on the bottom instead of the flat bottom. Also no forming wrinkles.
flame arrestor is missing on this air cleaner, avail at parts houses.

70 Chevelle

The air cleaner from the 69 Camaro was refined for the 70 Chevelle cowl induction. The bottom ridge was formed, maybe to help the stiffness. The forming wrinkles remained. Later "over the counter" GM air cleaners were of this design, what is know as a service part.

Closeups of the inside
Original

Repro

70 Chevelle


continued below

[ 06-06-2004, 06:50 PM: Message edited by: KevinW ]

[KevinW]

Group bottom shoot


Original bottom

Notice the large metal tube for the valve cover breather bent at 90 degrees and the bottom of the automatic temp sensor. There is also a small clip welded to the bottom to hold the vacumm tubes for automatics cars only. Good shot of the flat bottom and the wrinkles.

Repro bottom

There is the bottom ridge again and no wrinkles. The metal pipe is bent with two 45 degree bends instead of one 90 degree.

70 Chevelle

Metal tube has one 90 degree bend and forming wrinkles, but has the bottom ridge.

Last but not least, the 70 Chevelle's seal ring has a notch cut out of it.

The 69 Camaro's is a complete circle.

So, look for a flat bottom with forming wrinkles and a 90 degree tube to find an original ZL2 air cleaner. Hope this helps in your swap meet searching or Ebay hunting!

[ 06-06-2004, 06:46 PM: Message edited by: KevinW ]

[Unreal]

Kevin,
Great information. Wish I had it when I was searching out a correct 69 base. You gave me good info, but I had to use my "visualization" skills. One Picture worth Thousand words!!!

I would make one comment. I'm fairly certain that my setup is original. I got it from a guy who removed it from his Z/28 in the early 70's. On it, the Sealing Ring ID and OD are concentric for about 270*. For the other 90*, the OD curves in so that the flange is about 1" narrower in that area.
Sorry, I don't have it here to measure precisely.

Has anyone else seen the same thing?

[click]

awesome job Kevin thanks so much. Maybe we can get this held in permanent notch similar to Martins Basics. [img]graemlins/thumbsup.gif[/img]

[KevinW]

Thanks guys! I caught a break, when my friend picked up a z11 with an original on it and he had a repro. Thanks Bruce! [img]graemlins/beers.gif[/img]

Then all I had to do is take the pics and type it up. I still have a question on the pipe diameter, but this was enough info to help others identify the correct one.

[William]

This is good info, I'd like to add a few details.

There are 2 vent tube sizes: 3/4" for 350" and 1" for Z/28 and BB. The Z/28 uses a special rubber hose to connect the 1" air cleaner tube to the 3/4" rocker cover elbow. That means that a 350/manual trans duct hood air cleaner body is also unique as it will have the smaller tube.

A friend recently examined a 1 owner unrestored '69 Z/28 built Sept '69 and it has the ridged body air cleaner.

The vent tube with the 2 45º bends is necessary to clear the rear pump on a Holley double-pumper carb. The 90º tube contacts the rear pump causing constant fuel flow.

Spacers were used to elevate the flange/seal assembly in most applications. BB '69 Camaros did not require one; Z/28s used a short one [1-1/2"?] 350s a taller one [3-1/2"?]. '70-up Chevelles had a smaller unit that mounted on the carb.

The hold down stud in the carb is longer for duct hood applications. The wing nut was natural finish. For '69 Camaro 302/350 the coil bracket was changed to the one used on '65-'67 275/327. The standard bracket positions the coil more upright and it will contact a duct hood air cleaner.

'71-'72 air cleaners have additional differences; one being the snout is angled downward.

For several years in the late '70s service air cleaners were supplied with chrome lids creating the belief that was OE. OE duct hood cars never used chrome lids.

[69SSConvertible]

I am interested in determining if my cowl hood is an original GM hood. Any clues on how I can tell?

[Mark C]

Original to your car, or just an original hood? When was your car built, month and year? If it's before January of 69 then it's not original to your car, but might be an original hood.

http://www.camaros.net/cgi-bin/forum...c/3/5068.html?

[z/27 camaro]

Great info Kevin W !!
i got a couple of related questions i hope you can answer for me.

1] do all the ZL2 bases fit both the 780 holley carb and the SS quadrajet carb?

2] as "william" says "The vent tube with the 2 45º bends is necessary to clear the rear pump on a Holley double-pumper carb. The 90º tube contacts the rear pump causing constant fuel flow" ......the stock carb on the z/28, 396, and 427 is a vacum sec 780 holley, so then is his statement true??

3] is the position of the snorkel [ at say 8 oclock ] the same on all the ZL2 bases? what if you have stock A/C? do the bases still fit??

4] is the sensor for the air valve still availible? and the vacum hoses?

5] why does the chevelle seal ring have the flat spot on it?

thanks Kevin and anyone else that has some info. [img]smile.gif[/img]

[Mark C]

1] do all the ZL2 bases fit both the 780 holley carb and the SS quadrajet carb?

Yes I had mine on a 600 Holley for a while, you just lose the alignment tabs that keep the air cleaner "clocked" on the carb, since the holleys don't have the alignment key on the top like the quadrajets do.

2] as "william" says "The vent tube with the 2 45º bends is necessary to clear the rear pump on a Holley double-pumper carb. The 90º tube contacts the rear pump causing constant fuel flow" ......the stock carb on the z/28, 396, and 427 is a vacum sec 780 holley, so then is his statement true??

On originals yes, the repros may have moved the vent tube slightly to fit. They don't hit on an 1850 Holley.

3] is the position of the snorkel [ at say 8 oclock ] the same on all the ZL2 bases? what if you have stock A/C? do the bases still fit??

Yes, see the picture in my signature.

4] is the sensor for the air valve still availible? and the vacum hoses?

Yes, at NAPA and the like, but the repro's don't have the air doors in the snorkel, and you would have to drill the base for the sensor if you wnated to install them.

5] why does the chevelle seal ring have the flat spot on it?

Assume it's to clear the distributor and ignition coil.

[z/27 camaro]

Mark C
i was looking at the pic of your motor.......very nice........what kind of throttle rod do you have with the cowl induction air cleaner? is it the stock quadrajet rod, [ fairly straight with a couple of small bends in it ]or is it the z/28 throttle rod? [ that is 2 piece and has a big bend in it ]

[Mark C]

It's an old repro (1987 or so) throttle rod that Classic Industries listed (maybe they still do?)as the correct one for the 350/300 engine, but it's not the correct one for the L48. I think it's the base 2BBl or maybe the LM1/L65 throttle rod. I had to shorten it about an inch and extend the threads to get it to work right with the Quadrajet (stock) on my car.

[z/27 camaro]

Mark C
thanks for all the info.
ive never seen a ZL2 repro for the automatic in any of the catologs....who sells them? do you know?
i see the vacum sensor and clip can be bought tho.
also my ques about the air cleaner hitting the pump on a double pumper i dont understand your reply. the stock carb is a single pump vac sec carb. i dont think thats why there is 2 45 degeee bends on the repro's and not on the originals. i dont no why they are diff, so i was asking opinions.
[img]smile.gif[/img]

[Mark C]

No body sells them, but mines a repro. I cut a snorkel off of another air cleaner (make sure you get one from a 16" diameter air cleaner) that had a preheater valve on it and had it welded onto the repro body note the vacuum hose face frontwards instead of backwards. I could flipthe vacuum motor over but haven't got to it yet.

Don't know why the repro has 2 45 degree bends in it. Maybe it's easier to make two 45's then a single 90 with the tooling they had. Actually, I need to look at mine because I think mine has a single 90 degree bend in it. Maybe mine is a Chevelle air cleaner or a repro of a Chevelle air cleaner since I've had it for close to 20 years.

[z/27 camaro]

Mark
interesting info. correct me if im wrong but the pics above show the vacum line coming off the back of the preheater valve ie: the hose going towards the firewall if the air cleaner is on the car.
i just picked up an original auto ZL2 air cleaner off e bay with the filter and black lid for 60.00 US. i figured that was a great deal. i dont no yet if it has the sensor and clip on it or not, or if the pipe is a 90 or 2 45's but he says its an original used air cleaner.
he was selling it cause it wouldnt fit with his A/C. hence my question above about stock A/C.
his lose my gain.....i hope [img]smile.gif[/img]