A/C muffler

[Dale C.]

Re: A/C muffler


Thanks to all
Dale

[Joe L.]

Re: A/C muffler

All------


I haven't involved myself in this post, but will now do so at Dale's request.

First, let me say this: I do not have very much familiarity with AC systems of any C2 or C3 era car. I just have never paid very much attention to them and, thus, have little empirical knowledge. I have to defer to those that have made a lot of observation through the judging or other processes.

Having forwarned of the above, my belief has always been that the "binocular" style was the style muffler assembly used for 1967 through, at least, 1970. That's also the configuration shown in the AIM. I agree with Terry that the drawings shown in the AIM are not always accurate. However, I have generally found them to be surprisingly accurate, even with respect to details that were not really important. Also, and most curiously, the 1967-71 AIM's depict the "binocular" configuration assemblies BUT the 1972 depicts the rectangular configuration. It would seem very strange to me that the 67-71 would actually be the rectangular configuration but be depicted as the "binocular" while the 72+ were actually of the "binocular" configuration but be depicted as the rectangular.

There were several different assemblies used over the years. These are as follows:

1967-----

GM #3895917---small block and ALL SERVICE; superceded by GM #3923139 in October, 1971
GM #3885128----big block; superceded by GM #3895917 in October, 1966.

1968-----

GM #3923139--all apps; discontinued in May, 1986 and replaced by GM #10054561 which was discontinued without supercession in March, 1999

1969----

GM #3949927---small block PRODUCTION
GM #3949929---big block PRODUCTION and SERVICE
GM #3963760---small block SERVICE

1970-----

GM #3992144---small block PRODUCTION
GM #3939928---big block PRODUCTION and SERVICE
GM #3963760---small block SERVICE

1971----

GM #3963760---small block PRODUCTION
GM #3949928---big block PRODUCTION
GM #3992144---small block SERVICE

1972 ---

GM #3998438----small block PRODUCTION and SERVICE
GM #3998472----big block PRODUCTION and SERVICE.

There were a variety of supercessions from a former to a later part number. However, by later 1972, all of the 1969-71 assemblies had been discontinued and replaced by the 1972 assemblies, GM #3998438 and 3998472. The 3998438 then stuck around until October, 1995 when it was replaced by the GM #12529015 which was discontinued without supercession in January, 1997. The 3998472 was discontinued without supercession in November, 1985.

It is very possible that BOTH the "binocular" and rectangular style assemblies were used during the 1967-72 period. In fact, the multiple part numbers used during the 1969-71 period might provide a "hint" that there were 2 different configurations used. However, if I were to take an "educated guess" here based on the little that I've observed and the aforementioned parts information, I'd have to say that the 67-71 likely originally used the "binocular" style and the 72+ (including all 1969-71 SERVICE after late 1972) used the rectangular style.

[Dick W.]

Re: A/C muffler

I have a '69 hose set hanging on the wall in the shop. It has the rectangular block. I have never seen a '69-'72 with an orginal hose set that had the "binocular" block, only the rectangular. But then again I have not been looking at these cars much over 30 years

[Dale C.]

Re: A/C muffler

Joe
Thanks, this is kind of like talking with your broker and picking a winning stock. Getting it right is a crap shoot.
Dale

[Terry M.]

Re: A/C muffler

Dale,
I would expect to see the rectangular, or boxed type on original AC systems for 1969 to 1972. I think the connection tot he AC Compressor would be the same for 1968.

The style shown, commonly referred to as the binocular style, is a later (somewhat after 1972) SERVICE replacement.

BTW: Original muffler assemblies from 1968-1972 should have brass hexagonal rounded-top nuts that are tin plated. Some will have a manufacturer's logo on one of the flats.

Please note that no place in my post is 1966 or 1967 mentioned -- AND I only guessed that 1968 [b}MIGHT[/b] be the same as later muffler assemblies.

So I make no claims about 1966, 1967 OR 1968 muffler assemblies -- except for what I think about 1968. I am, however sure of what I have seen regarding 1969 to 1972.

I am sorry for your confusion, but it would help y'all if you read and understood what I wrote, NOT what you think I wrote. I am encouraged that Noland has so many pictures of cars with the part you need for 1966 and 1967. Too bad he didn't continue his work so that us C3 people could have the benefit of his research, but alas it is not so. We have to observe original cars on our own and record those observations in the respective TIM&JGs.

Most of you who have been on this forum for any length of time should know that you will almost never see me posting about C1 or C2 subjects. As someone else said: "I know nothing!"

[Bryan M.]

Re: A/C muffler

The M. F. Dobbins 68-72 Fact book shows the block style a/c muffler on all a/c equipped cars in the book.

[Peter L.]

Re: A/C muffler

Scott - I agree with Larry. The 2nd Schraeder valve was removed with the change to the POA. It's interesting to note that the original mufflers on early 67 C60 Corvettes had the port for the 2nd Schraeder valve on the side of the base piece "welded" closed and you can see the evidence of that becasue there is a slight build up of material. Later versions have no evidence that there was a 2nd port for another Schraeder valve on the base piece as that side surface on base is flat. Pete

[Jack H.]

Re: A/C muffler

I was confused when I read Terry's comments that the "binocular style" was a later service replacement (post-1972), and then confused more when I checked the Adams book and the pictures of the midyears showed both kinds.

Terry and Dick are RIGHT. The 'binocular' style manifold IS a service replacement style for the Shark cars this thread was initiated on... For a while, there was a service replacement 'block' style manifold available through service (one for SB/another for BB), but even those can be detected by knowledgable judges since they're intended to be 'spliced' into the existing, broken, hose system via hose clamps vs. the factory original permanent crimp style connectors.

The problem here is mixing 'metaphors'....comparing mid-year to Shark AC system components and thinking they were the same. Not true...

Last, the 'binocular' style A/C manifolds (including attached hoses) can still be purchased through service, but there's a Catch-22. The attaching bolt threads into the compressor through the center hole in the 'binocular' and that's rather soft, thin-walled, aluminum compared to the factory original BLOCK.

It's not uncommon for the replacement manifold to fatigue fracture at this center hole allowing the in/out hoses to separate and the car to loose its R12! While GM considers the service replacement hose setup with the binocular style manifold to be a legitimate replacement part, there's something they're not saying...

On passenger cars from the era that used that style manifold, they also installed a STEEL plate that he attaching bolt went through. That plate would spread the insertion force of the bolt across both sides of the binocular and thwart the potential for the manifold assy to crack at the center when exposed to cradle rock side loading stress.

So, if you're forced to use a service replacement, binocular, style hose/manifold setup, go a step further and get/install the steel plate!

[Joe L.]

Re: A/C muffler

I was confused when I read Terry's comments that the "binocular style" was a later service replacement (post-1972), and then confused more when I checked the Adams book and the pictures of the midyears showed both kinds.

Terry and Dick are RIGHT. The 'binocular' style manifold IS a service replacement style for the Shark cars this thread was initiated on... For a while, there was a service replacement 'block' style manifold available through service (one for SB/another for BB), but even those can be detected by knowledgable judges since they're intended to be 'spliced' into the existing, broken, hose system via hose clamps vs. the factory original permanent crimp style connectors.

The problem here is mixing 'metaphors'....comparing mid-year to Shark AC system components and thinking they were the same. Not true...

Last, the 'binocular' style A/C manifolds (including attached hoses) can still be purchased through service, but there's a Catch-22. The attaching bolt threads into the compressor through the center hole in the 'binocular' and that's rather soft, thin-walled, aluminum compared to the factory original BLOCK.

It's not uncommon for the replacement manifold to fatigue fracture at this center hole allowing the in/out hoses to separate and the car to loose its R12! While GM considers the service replacement hose setup with the binocular style manifold to be a legitimate replacement part, there's something they're not saying...

On passenger cars from the era that used that style manifold, they also installed a STEEL plate that he attaching bolt went through. That plate would spread the insertion force of the bolt across both sides of the binocular and thwart the potential for the manifold assy to crack at the center when exposed to cradle rock side loading stress.

So, if you're forced to use a service replacement, binocular, style hose/manifold setup, go a step further and get/install the steel plate!

Jack------


As I think about it, I think you're one of the guys that once lead me to believe that the "binocular" style was the original style used for early C3's.

[Joe L.]

Re: A/C muffler

The M. F. Dobbins 68-72 Fact book shows the block style a/c muffler on all a/c equipped cars in the book.

Bryan-----


Yes, it does and I'd say that my "educated guess" looks like it's now not so "educated".

The thing that's most interesting about the photos is that the 1972 assembly shows the rectangular block style. As I mentioned earlier, the 1972 assemblies, GM #3998438 for small blocks and GM #3998472 for big blocks, became the SERVICE part numbers for 69-72 Corvettes for years. The 3998438 was replaced by the 12529015 in October, 1995, but it only lasted a few years before it was discontinued without supercession. The big block assembly, GM #3998472 was never replaced and was discontinued without supercession in 1985.

So, if the 1972 assemblies used the rectangular block style (as the Vette Vues photo shows), then the SERVICE replacements for all 1969-72 "should" have been the rectangular block style, too. However, what must have happened was that, at some point, the block style changed without a change in part number. What may have happened is that later C3's with A-6 compressor used the "binocular" style. While those assemblies are different than the 69-72, the block style may have been "standardized".

[Scott S.]

Re: A/C muffler

Scott - I agree with Larry. The 2nd Schraeder valve was removed with the change to the POA. It's interesting to note that the original mufflers on early 67 C60 Corvettes had the port for the 2nd Schraeder valve on the side of the base piece "welded" closed and you can see the evidence of that becasue there is a slight build up of material. Later versions have no evidence that there was a 2nd port for another Schraeder valve on the base piece as that side surface on base is flat. Pete

Thanks for the information Pete, I'm learning.

I thought last night I might have some additional help for Dale. I forgot about a book I had until I saw Bryan's comments (post 21) about the M.F. Dobbins Fact Book for 68-72, which reminded me of my "1969 Stingray Guidebook" by Rick Bizzoco. The cover has a "1968-1969" sticker pasted over the "1969" in the title, but it's only for 1969. Great book for the '69, but not much help for this specific discussion, and it didn't show a picture of the A/C muffler in the air-conditioning section anyway.

I also checked all of my old books that weren't specific to midyears:

Corvette - Fifty YearsThe Classic CorvetteCorvette TroubleshootingCorvette Weekend Projects - Maintenance and Repair How-Tos for 1968-1982 CorvettesCorvette: A Piece of the Action - Impressions of the Marque and the Mystique 1953-1985Chevrolet Corvette Restoration Guide1968 A/C muffler anywhere... I don't have the M.F. Dobbins book that Bryan referred to.

[Joe L.]

Re: A/C muffler

Thanks for the information Pete, I'm learning.

I thought last night I might have some additional help for Dale. I forgot about a book I had until I saw Bryan's comments (post 21) about the M.F. Dobbins Fact Book for 68-72, which reminded me of my "1969 Stingray Guidebook" by Rick Bizzoco. The cover has a "1968-1969" sticker pasted over the "1969" in the title, but it's only for 1969. Great book for the '69, but not much help for this specific discussion, and it didn't show a picture of the A/C muffler in the air-conditioning section anyway.

I also checked all of my old books that weren't specific to midyears:

Corvette - Fifty YearsThe Classic CorvetteCorvette TroubleshootingCorvette Weekend Projects - Maintenance and Repair How-Tos for 1968-1982 CorvettesCorvette: A Piece of the Action - Impressions of the Marque and the Mystique 1953-1985Chevrolet Corvette Restoration Guide1968 A/C muffler anywhere... I don't have the M.F. Dobbins book that Bryan referred to.

Scott-----


The photos in the Dobbins book that shows the rear area of a 1968 A/C compressor appears to show the rectangular block configuration.

Also, I believe the "1968-69" label applied to the cover of the 1969 Guidebook you mention was done by David Crane, the exclusive distributor of the book. When I ordered my copy from him, I asked him to not apply said label to the cover of the one he sent me and he did as I asked..

[Scott S.]

Re: A/C muffler

Scott-----


The photos in the Dobbins book that shows the rear area of a 1968 A/C compressor appears to show the rectangular block configuration.

Also, I believe the "1968-69" label applied to the cover of the 1969 Guidebook you mention was done by David Crane, the exclusive distributor of the book. When I ordered my copy from him, I asked him to not apply said label to the cover of the one he sent me and he did as I asked..

You are correct!

On the Acknowledgments page of the 1969 Guidebook (right after Contents page), just below "David Crane - Crane's Corvette Supply" in bold-face, there is a yellow sticker with a red outline, the size and shape of a mailing label. Over this sticker are two blank white mailing label stickers, but I can still make out "Crane's Corvette Supply" with contact info underneath the blank white stickers.

Must be NOS...

[Dale C.]

Re: A/C muffler

Jack
Could it be that the flimsy design or inadequate construction is why that 68 only production muffler 3923139 is so scarce and over the years most were probably replaced in service with the hardier box type? A follow-on question, it appears that 68 and prior, mufflers had the barbed end and required the hose clamp while the 69 and on used the crimped version. If this is so, they are not compatible, and would require some adaptation to work with the crimped hoses of 69 and on. I presently have that 67 version on my 68 car and now wonder if it came that way or maybe was later replaced, with that 67 version out of necessity due to that failure you spoke of. Jack, what would you do leave the older version 67 on or change to the light weight 3923139, with steel plate? Looks like a flat washer would work. I am changing the compressor out for other reasons anyway. I am also curious about that steel support you spoke about, what it is, where its goes, and where to find one? I'll send a side by side of the two muflers.
Dale

[Terry M.]

Re: A/C muffler

On occasion I have found myself judging Corvettes with rubber bumpers. I have seen some of those cars with the binocular style air conditioning manifold/muffler assemblies, and I have been assured by those more familiar with those cars than I that style is correct for those cars. I can not tell you exactly what year Corvettes I was judging, but we don't go too far into those C3s before the A6 gives way to the rotary compressor.

To confirm what others have said above -- In general I expect 1968 Corvettes to use the air conditioning type worm-style hose clamps between the AC manifold and the hoses, and 1969 to use crimped connections at this point. We don't see too many 1968s in flight judging, and of course fewer yet C60 examples. One might spend a lot of time speculating about the reasons for that, but regardless the reason the end result is we don't have a real good data-base of 1968 examples to build a knowledge base. So if one were to ask for an exact change point, a lot of shoulder shrugs would be the result.

That crimped connection can be removed, and the hose replaced and reattached with a worm-type AC-style clamp -- so a service replacement manifold unit could be used to effect a repair of the crimped style manifold/hose assembly. How "legal" that might be would be a whole other can of worms that I would prefer to leave alone. I only mention it because of your state of residence. If one were to ask a professional AC shop to do this, I suspect it might result in issues.