A.I.R pump on L-48 w/A.C?

[Tom Sarno]

My '74 came to me missing most of the original parts. If it wasn't for the body you would think it was a cross between an Impala and a Pickup. I am collecting all the missing parts while doing a frame off. The car has A/C but does not have the A.I.R. pump. I came across another '74 that was being parted out and it still had the pump and brackets but was not equipped with A/C. The problem is the pump mounts were my A/C is now. Was the pump mounted lower on A/C cars or is my A/C compressor in the wrong place? Any help would be appreciated.

Tom

[Joe L.]

Re: A.I.R pump on L-48 w/A.C?

Tom-----

As far as I know, the AIR pump mounting was the same for cars with and without A/C. However, I think that it's possible that your car did not originally have AIR. My recollection is that there was one 1974 application that was not originally equipped with the AIR system. If I recall correctly, that application was 1974 L-48 with auto trans and FEDERAL emissions. That would be engine suffix code "CLA", but I'll check on this later and confirm or correct.

[Craig S.]

Re: A.I.R pump on L-48 w/A.C?

Tom - I have a 74 that is in restoration too, but I am the 3rd owner since I bought it in 1977 and all parts are original. I also have the AIM for 74. My car definitely has A.I.R. and C60. It is an L82, 250HP. The A.I.R. Pump mounts inboard of the AC compressor as I recall. I will check the AIM tonight when I get home....Craig

[Craig S.]

Re: A.I.R pump on L-48 w/A.C?

Joe - I forgot to mention my codes - it's a Federal emissions car with a Muncie M21 (was built in Oct 73 with 6823 being the serial) so it got a Muncie versus Borg Warner close ratio. The engine suffix is CLR. Later!....Craig

[Joe L.]

Addendum

Tom------

Well, my recollection did not fail me this time; 1974 Corvettes with L-48, auto trans and FEDERAL emissions (i.e. cars not originally delivered in California) were not equipped with the air injection reactor system and the engine suffix code for such applications was "CLA". If your car is an L-48 with auto, the chances are it was not originally equipped with AIR; if it still has the original engine block and the suffix code is "CLA", then it was definitely not originally equipped with AIR.

If your car is manual trans equipped, then it DID have AIR. In this cae, the suffix code will be "CKZ" or "CLB". If you have an automatic trans, but engine suffix code "CLC" (i.e. an original California-delivered car), you should also have AIR.

For 1974 Corvettes, the A/C compressor was basically mounted to the right of the right side valve cover. The AIR pump was mounted more-or-less above and to the left of the right side valve cover. Consequently, there is no interference between the two.

[Michael W.]

Re: A.I.R pump on L-48 w/A.C?

Tom,

Your question got my curiousity up. As far as I know the same hardware is applicable for model years '73 and '74. I wanted know if the AIR Pump mounting bracket is different for AC and non-AC cars. According to my AIM, they are indeed the same.

The difference in mounting config. on a non AC car is a spacer which is added behind the bracket on the lower mounting bolt hole location where the bolt enters the block. On AC cars this spacer is not required, as the gap is occupied by the upper inboard corner of the AC mounting bracket.

If you cannot achieve this mounting arrangement with your AC bracket (assuming your newly aquired AIR bracket is correct) I can only imagine that the AC bracket is incorrect, possibly from a '76 and up car with a different style compressor.

[Joe L.]

Re: A.I.R pump on L-48 w/A.C?

Mike-----

Yes, ALL 1966 to 1979 small block AIR pump brackets are functionally the same and interchangeable even though 3 different brackets were used----GM #3882861 from 1966-67, GM #3923214 from 1968-1977, and GM #14007354 from 1977-78 and, later, to SERVICE all 1966-79 Corvette with AIR applications. Therre were no other brackets used for 66-79 small block AIR pumps regardless of other engine equipment installed on a particular car. All of these brackets are now GM-discontinued.

The spacer which you referred to for non-AC applications was GM #3877600 and it's still available from GM for $1.45.

[Tom Sarno]

Re: Addendum

Joe,

I believe the car was a four speed but the frame was swapped out before I got it. The frame that the body was on has a welded in crossmember and clutch peddles are inside the car with an automatic console. The radiator is for a four speed car and has a plastic shroud. The A/C dryer and evaporator is also still in place. I bought with an th350 automatic trans and a truck block. The A/C brackets were in the car(behind the seat) when I got it. I want to put it back as original as possible. Is there some other clues to tell if it was a stick or auto? Was it possible to get the L-48 with a stick and A/C? If it was available, would it require a special gear ratio in the rear? It also has power brakes and steering with power windows, but I don't think that makes a difference one way or the other.

Thanks for your help

Tom

[Michael W.]

Re: Addendum

Tom,

I guess your tank sticker is long gone and that this is not a Canadian car, either would tell you for sure the exact delivery configuration. Your engine stamping pad is gone so that clue is gone with it. Your engine would have been CKZ four speed or CLA for TH400 if it is a non-California car.

In 1974 you could get just about any combo of options you wanted, so L-48 four speed or TH400 with AC were equally available. Standard rear axle ratio for L-48 four speed in 1974 was 3.36 and auto trans was 3.08. The two same ratios were available as options however, so without knowing if your diff. is original and was the standard ratio again this may not determine what the original type of trans was.

Did you figure out your AC bracket dilema?