Need help with 73 A.I.R Pump brackets & hardware

[Dennis H.]

I have been round and round researching what I need for hardware to re-install the A.I.R. system on my 1973 350 L82, PS, AC & A.I.R.

I have everything I need with the exception of the hardware to mount the A.I.R bracket and brace.

First Issue
The 1973-1974 3rd edition TIM & JG shows the A.I.R brace to water pump (WP) mounting on page 144 Fig M12.6 and the AIM at UPC 6T Sheet 2. The TIM & JM show a third brace at the WP and the AIM doesn't. What is the correct stack up of braces at this location? See attached pictures.

Second Issue
I know at the WP I need a stud, couple lock washers and a nut for the lower A.I.R. brace, at the upper brace a bolt and washer. For the A.I.R. bracket I'm assuming a bolt and lock washer thru the AC bracket and bolt and lock washer at the intake. Problem is I can't find anything in the AIM or GM IPB manual addressing the mounting of this bracket.

Does anyone have pictures of these areas for how the bracket and brace is attached? Lastly, where do I source this hardware from? Not seeing anything on the usual vendor websites.

I would like to have the correct hardware but will settle for what works if I can figure out what I need.

Thanks
Dennis

[Joe L.]

Re: Need help with 73 A.I.R Pump brackets & hardware

I have been round and round researching what I need for hardware to re-install the A.I.R. system on my 1973 350 L82, PS, AC & A.I.R.

I have everything I need with the exception of the hardware to mount the A.I.R bracket and brace.

First Issue
The 1973-1974 3rd edition TIM & JG shows the A.I.R brace to water pump (WP) mounting on page 144 Fig M12.6 and the AIM at UPC 6T Sheet 2. The TIM & JM show a third brace at the WP and the AIM doesn't. What is the correct stack up of braces at this location? See attached pictures.

Second Issue
I know at the WP I need a stud, couple lock washers and a nut for the lower A.I.R. brace, at the upper brace a bolt and washer. For the A.I.R. bracket I'm assuming a bolt and lock washer thru the AC bracket and bolt and lock washer at the intake. Problem is I can't find anything in the AIM or GM IPB manual addressing the mounting of this bracket.

Does anyone have pictures of these areas for how the bracket and brace is attached? Lastly, where do I source this hardware from? Not seeing anything on the usual vendor websites.

I would like to have the correct hardware but will settle for what works if I can figure out what I need.

Thanks
Dennis

Dennis------


The stack-up is exactly as shown in the JG photo-----from the pump leg it's alternator bracket, alternator brace, split lockwasher, stud, AIR brace, split lockwasher, nut. The stud was originally GM #3889313 but was never available in SERVICE. The original SERVICE stud was GM #3877646 but it was discontinued in 1976. The last available stud was GM #461318 but it was also discontinued without supersession quite a few years ago. Reproductions are very easy to obtain.

The AIR bracket was installed at the engine plant so nothing will be found in the AIM. But, attachment hardware is very simple: the bracket attaches to the intake manifold with the end manifold attaching bolt. This is a bolt that's about 3/8" longer than the other manifold bolts. Usually, it will have a different headmarking than the other manifold bolts. At the lower end it uses a standard hex head bolt. I've forgotten the length.

[Dennis H.]

Re: Need help with 73 A.I.R Pump brackets & hardware

Thanks, Joe for the hardware info. On the Alt bracket I'm just not seeing that attached to the WP, see picture attachment of AIM UPC 6Y Sheet 1 and my car. I'm pretty sure my car has the original Alt bracket installed.

Maybe an Alt strap or brace I'm missing????

[Joe L.]

Re: Need help with 73 A.I.R Pump brackets & hardware

Thanks, Joe for the hardware info. On the Alt bracket I'm just not seeing that attached to the WP, see picture attachment of AIM UPC 6Y Sheet 1 and my car. I'm pretty sure my car has the original Alt bracket installed.

Maybe an Alt strap or brace I'm missing????

Dennis------


I thought that 1973 still used the stamped steel alternator brace as pictured in the JG photo. However, maybe that changed to the cast iron brace for the 1973 model year or sometime during the 1973 model year.

What is the configuration and casting number of your left side exhaust manifold?

[John S.]

A2673846-FBCB-4F10-B75C-A6487C46787A.jpg

7F48D0A3-F686-4074-B625-FB9EDB60D068.jpg

[Dennis H.]

Re: Need help with 73 A.I.R Pump brackets & hardware

John thanks for that picture. That spacer is missing on my car, I see it in the GM IPB (Rev 12-83) at find # 14 and ref to GRP 2.277 under PN 3825451 but no dimensions. The spacer for a 74 is .42 ID X .69 OD X .256 Long.

The stamped steel Alt bracket that would attach to the WP ran up through 72 and the 73 model year went to the iron bracket. It would appear the picture (Fig M12.6) in the 73-74 TIM/JG is incorrect and for reference only as to how the Alt adjusting brace attaches.

I think I broken the code on what hardware I need, just need to find it now. OEM original would be my first choice but that's a crap shoot and a lot of internet dumpster diving.

My car is 90% original just trying to undo some past Johnny Hot Rod mods. On the plus side, aside from A.I.R. system I have everything that was pulled off the engine that owner #1 had the foresight to keep.


Joe, the exhaust manifolds are PN 3932461 RH on both sides.

[Joe L.]

Re: Need help with 73 A.I.R Pump brackets & hardware

[QUOTE=



Joe, the exhaust manifolds are PN 3932461 RH on both sides.[/QUOTE]


That would be further evidence that your car was originally built with the cast iron alternator bracket. However, I'm still not sure that all 1973 small blocks used the cast iron alternator bracket.

[James G.]

Re: Need help with 73 A.I.R Pump brackets & hardware

My brother's 73 L82 with 30k miles and engine never out, exhaust never off the manifolds has the cast iron alt bracket. built October 11 1972

[John S.]

Re: Need help with 73 A.I.R Pump brackets & hardware

Dennis, glad you were able to figure it out, good luck finding the rest of parts you need. Also good to hear the previous owner saved most of the original system.

The smog pump bracket itself is pretty straight forward, it mounts to the top bolt of the WP on the right side with the cast A/C mounting bracket sandwiched between the smog bracket and the WP. The top part of the pump bracket uses the right front intake manifold bolt, the only thing to note is that you will probably need a longer bolt in each location to compensate for the thickness of the smog pump bracket.

Let me know if you need any more photos or any other details, good luck !!

[Joe L.]

Re: Need help with 73 A.I.R Pump brackets & hardware

John thanks for that picture. That spacer is missing on my car, I see it in the GM IPB (Rev 12-83) at find # 14 and ref to GRP 2.277 under PN 3825451 but no dimensions. The spacer for a 74 is .42 ID X .69 OD X .256 Long.

The stamped steel Alt bracket that would attach to the WP ran up through 72 and the 73 model year went to the iron bracket. It would appear the picture (Fig M12.6) in the 73-74 TIM/JG is incorrect and for reference only as to how the Alt adjusting brace attaches.

I think I broken the code on what hardware I need, just need to find it now. OEM original would be my first choice but that's a crap shoot and a lot of internet dumpster diving.

My car is 90% original just trying to undo some past Johnny Hot Rod mods. On the plus side, aside from A.I.R. system I have everything that was pulled off the engine that owner #1 had the foresight to keep.


Joe, the exhaust manifolds are PN 3932461 RH on both sides.

Dennis------

The GM #3825451 spacer is definitely NOT what you need. That spacer is about an inch or more in length. Basically, the spacer you require mimics the thickness of the stamped steel alternator bracket which is about 1/4" in thickness. So, it sounds like what you describe as the 1974 spacer is what you need. Essentially, it's nothing more than a thick washer.

[John S.]

Re: Need help with 73 A.I.R Pump brackets & hardware

A bit more information regarding the thickness of that spacer in my earlier post. 1/8” was my initial estimate based on getting a caliper in there and kinda eyeballing it. Here’s another close up shot using a drill bit as a thickness gauge. That’s the shank of a 11/64” (.172) dia. bit in the photo.

CD137D84-BB9A-4C0D-B43A-0BCF4C68D698.jpg

[Dennis H.]

Re: Need help with 73 A.I.R Pump brackets & hardware

John thanks for that picture, just what I was looking for.

Dennis

[Jimmy P.]

Re: Need help with 73 A.I.R Pump brackets & hardware

Hi Dennis,
Heres a shot of the bracket set up from a '74 L82. To confirm the statements above. You can see that the "spacer" is still being used. Thanks to John's photo above...I agree with Joe in that we can probably get by with a washer with the same thickness, without any problem. I say (we) because I don't have this part on my car either. When restoring, I didn't see it in the AIM. Looking at my alternator adjusting brace, it doesn't seem to be noticeably out of line at all, without it. Anyway, I've also made a note to update that photo/text on page 144 in the 73-74 Judging Manual to reflect this in the future.

[David C.]

I was working on this part of my car tonight. (The items on the bolt/stud were in the wrong order). Anyway, I found that the spacer on my late (May 31 build date) 73 has part number 9522047. I don't know if it's original or not.

9522047.jpg

[Joe L.]

I was working on this part of my car tonight. (The items on the bolt/stud were in the wrong order). Anyway, I found that the spacer on my late (May 31 build date) 73 has part number 9522047. I don't know if it's original or not.

9522047.jpg

David----

It's possible that's a GM part number although I cannot find that any in the series 952xxxx were ever released. However, if it was a GM part number it was never available in SERVICE.