Camaro and Chevelle A/C flange differences.
 

Thought I would post this to show the differences between the 1969 Camaro ducted hood air cleaner flange and the 1970-72 Chevelle cowl induction air cleaner flange.

The '69 Camaro flange has its thinnest point around the nine o'clock position when installed. The GM part number of that flange is 3955230 and can be found in Group 3.417 in the parts book. That part was superseded to 3975986 on 12/71.

There are two different Chevelle air cleaner flanges that use the same part number 3975986. The early style shares the same continuous lip to hold the seal in place as the Camaro flange. There is one difference with the Chevelle flange. Approximately the eight o'clock position it has a flat spot that the Camaro flange does not have. I have taken a picture showing the early NOS 3975986 on top of a Camaro flange so you can see the difference. Not sure when the full lip Chevelle flange was changed to the sliced off flange but it must have been short lived. The box the NOS full lipped flange came in is dated February, 1970.

The most common Chevelle flange has the sliced off side of flange.

I have taken pictures of all the flanges to help identify them. First picture is a 1969 Camaro flange that has the rear sticker on it. Second picture is the NOS early Chevelle flange. The rest of the pictures are self-explanatory.

Original 1970 Chevelle road test pic.

William I have no idea what I am looking at.......

Flattened area on flange lip there to clear the can?

Why the ZL2 flange needed the flat spot on Chevelles. On A/C cars, the vacuum tank would contact the Camaro flange.

Warren's post cleared something up. The May '70 Hot Rod has a LS-6 Chevelle test. The engine bay photo clearly shows the flange is not the clipped version. I thought they must have continued the Camaro part but looks to be the second design. Possible only A/C cars got the clipped version.

Sorry, the photo won't scan.

I would say William's picture is to show the purpose of the sliced flange with the vacuum can.

Two things I do not understand about the Chevelle flanges. Usually when GM makes a change to a part they assign it a different part number. In this case we can see two different Chevelle flanges with same part number but are totally different looking.

The second thing I do not understand about the early Chevelle flange is why the flat spot in the eight o'clock position? Was there a clearance issue there?

- Warren

I sometimes think these engine components were designed way before they actually knew how much clearance would actually be needed.Maybe the early 8 O'clock flat spot design,was one of those.
Look at the Dual snorkel air cleaner for instance,the PCV valve depression on the drivers side bottom of it,was not even needed in reality.
Plenty of clearance.

That's part of ZL1 Camaro lore. They were supposed to be built with the Holley #4296 850 DP carb but most were built with the standard #4346 780. Why? If you mount the 1st design ducted hood air cleaner on an 850 the 90º vent tube contacts the rear pump lever. They later changed the tube to 2 45º bends so it clears the pump.