1966 then 1967 thru 1974 Big Block AC Brackets

[Mike B.]

Hi Guys,

When I bought my '66 427 AC convertible back in 1988 her AC compressor and brackets were missing. Through those early years of ownership I'd always thought that the compressor front and rear cast brackets were the same for the '66 thru '74 model years. I knew the '66 AIM had unique part numbers vs. the '67 and later cars, but I'd never seen a set of these brackets anywhere. Well, even if I had seen a real set it would've been very difficult to identify them from the '67 -'74 parts with them installed on the cars.

About 10 years ago I met a great guy through the NCRS Technical Discussion Board. He's very knowledgeable of the midyear AC system and components. He had a set of these 2 rare cast '66 only brackets. He posted some photos of the front and rear '66 427 AC brackets on the Forum. Finally! I knew what a real set looked like. Later that year he was kind enough to sell his brackets to me. These 2 brackets are shown here and will go on my '66 when I install my AC compressor.

Through the years since then I've been lucky enough to find 2 more sets of these rare '66 brackets. They are:

Front- #3887166
Rear- #3887165

The reason I'm posting this thread is to help those out there of what to look for when comparing these brackets from each other. Trying to help since this can be an expensive decision. During this thread I'll post numerous shots of the '66 only brackets. I'll then compare them alongside or to the '67 thru '74 AC compressor brackets. They are:

Front- #3894362
Rear- #3894364

Since my brackets are loose now this is the perfect time to show you all a good comparison of these parts. First, let's compare the '66 vs. the '67 thru '74 front brackets. The last photo is of the underside of these 2 parts. The '66 bracket is on the left with traces of orange paint. Enjoy. Mike

[Mike B.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Now for the side brackets. I recently bought a set of big block AC brackets online that reportedly came from an October '66 build date 1967 Corvette. Very early car. From the seller's photo I could clearly see the 1966 bracket numbers #3887166 and #3887165. But I've stumbled upon something very interesting to me. Although this side bracket has the correct '66 casting number #3887165, it's shape is very different from the other two sets of '66 only side brackets that I own. At first I was suspicious of the origin of these brackets. Maybe from a different Chevrolet model?

Through a recent thread of mine asking for help on this subject, I've been assured that these '66 bracket numbers are strictly for 1966 Corvettes. The two gentlemen that posted to my thread were extremely helpful with their knowledge of historic parts. We had a discussion about the possibility of these 2 1966 Corvette bracket numbers being installed on very early '67 Corvettes as the seller advertised. The discussion leaned that way slightly since the '67 AIM was redrawn Jan '67 when the later '67 thru '74 part numbers were listed.

I'm asking anyone for help that has or is restoring a Sep/Oct '66 build 1967 390/400hp Corvette with AC to please check out your side AC compressor bracket and compare it to the bare metal bracket shown in the following photos with casting #3887165 to please respond to this thread if it's the same as your car's!

You'll have to use an inspection mirror to view the numbers since they're under the bracket when it's installed on the right exhaust manifold studs there. The '67 thru '74 bracket numbers are visible from above so no mirror is required if you have the later style bracket installed.

This possible early '67 bracket #3887165 (2nd design) looks very similar to the later '67 thru '74 bracket #3894364 as it is lacking the additional pivot slot that's shown in these photos of the '66 bracket #3887165 (1st design). I'm very curious if this #3887165 (2nd design) bracket is for very late '66 and early '67 AC cars as a transition to the upcoming '67 thru '74 style?

Here comes the first set of rear brackets. When I show them together they are in this order:

Left - '66 #3887165 (1st design) Center - '66 #3887165 (2nd design) Right - '67 thru '74 #3894364 (dark black paint)

Any lone dark black painted bracket is the underside of the '67 thru '74 part.

Very interesting to me. I hope others out there find these historic bracket comparisons interesting as well. Here they come. Mike

[Mike B.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Here's 6 more shots of the evolution of these big block side AC compressor brackets. Please read the description in the 2nd post below.
Take care. Mike

[Mike B.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Correction to my 2nd and 3rd posts. Too late to edit. I have a bad habit of saying "side" bracket when I should say "rear" bracket as the parts catalogs state. However, these brackets are installed on the rear/side of the engine on the right exhaust manifold. In future posts if I say either we'll call them synonymous.

One more important bit of info for very early build 1966 Corvette 427 AC cars. The 1966 AIM was redrawn 6-17-'65 and shows the front AC bracket as #3887166 and the rear bracket as #3887165. Since this drawing date is before the production run for '66 I would assume that all '66 cars would have these numbers on their brackets. But I've just recently found out from fellow NCRS members that there was another list of bracket numbers found in the 1966 Corvette Parts Catalog dated Oct '65 that states the front AC bracket as #3883930 and rear bracket as #3883931. If any early '66 owners find either of these Oct '65 listed numbers on your car (or anywhere) please respond here! I've never seen either of these brackets before and this would be great info here!

Anybody out there? Mike

[Justin S.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Would the change be due to A.I.R provisions? Was there a change in the physical dimension of the compressor?

[Mike B.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Hi Justin,

I think the A6 AC compressors were unchanged for the '66 thru '67 models except that the cases changed slightly mid '66 production. Their ends were swaged (crimped). They remained that way afterwards. Their lengths were unchanged.

I don't think A.I.R. had any bearing on the information that I've provided on this thread. Anybody want to comment on this? Mike

[Mike B.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Good Morning Everyone,

Gonna give this thread another try.

Have any of you early '67 427 with AC car owners or restorers (especially resto shop owners) ever spot any '66 style rear compressor brackets installed on original cars? It's the one that attaches the compressor to the right side of the engine onto an exhaust manifold stud there. I'm especially interested to know which style your car has. I was hoping to get responses from Sep - Oct '66 built cars, but I'm also interested in any early '67 BB AC car that you've owned/seen.

Check out the #3 post to this thread by me. I've attached a black painted '66 style 3887165 bracket, then a later (unpainted) 3887165 bracket, then finally the '67 - 74 style bracket (dark black) listed in the '67 AIM.

I'm researching if the early '67 427 AC cars might have had leftover '66 style brackets. I'd sure appreciate your valuable inputs to my search.

Thanks guys,
Mike

[Darryl D.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

I did not see this one pictured anywhere?

https://www.corvetteforum.com/forums/c1-and-c2-parts/3979173-rear-ac-bracket-gm-3854060-a.html

My 1966 390 h.p. A/C car had it. It bolts to the intake manifold bolts and has a short steel strap the attaches to the back of the compressor.

[Mike B.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Hi Darryl,

That part photo that you show on the Forum as a '66 Corvette big block AC intake bracket is incorrect for the '66 and '67 Corvette model years. The U-shape bracket that they should have is part #3872726. See '66-'67 AIM C60 sheet C3 part #1 "Support". A heavy rod flattened on each end attaches to the back of the compressor then to this intake bracket.

Authentic pre-owned bracket #3872726 are still available on line as they were used on Corvettes and other big block AC Chevrolet cars. An authentic brace rod is very difficult to find these days as they were '66-'67 ('68?) Corvette only parts.

I agree with the guy that replied to your post on the Forum as to the application of your bracket there. I'm interested to see what front and rear BB AC brackets your '66 has as this is research for those two brackets. I've shown detailed photos here of what to look for.

Thanks Darryl.
Mike

[Darryl D.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Hi Darryl,

That part photo that you show on the Forum as a '66 Corvette big block AC intake bracket is incorrect for the '66 and '67 Corvette model years. The U-shape bracket that they should have is part #3872726. See '66-'67 AIM C60 sheet C3 part #1 "Support". A heavy rod flattened on each end attaches to the back of the compressor then to this intake bracket.

Authentic pre-owned bracket #3872726 are still available on line as they were used on Corvettes and other big block AC Chevrolet cars. An authentic brace rod is very difficult to find these days as they were '66-'67 ('68?) Corvette only parts.

I agree with the guy that replied to your post on the Forum as to the application of your bracket there. I'm interested to see what front and rear BB AC brackets your '66 has as this is research for those two brackets. I've shown detailed photos here of what to look for.

Thanks Darryl.
Mike

Sorry, I sold that car in 1993

[Mike B.]

Re: 1966 then 1967 thru 1974 Big Block AC Brackets

Thanks for moving this thread back to the top Darryl. Thought it was a goner. Yes, it would've been good to check out your brackets.

I hope this thread has informed some of you of the evolution of Corvette big block front and rear (side) AC compressor brackets from 1966 then 1967 thru 1974 production.

Please take a look from the start of this thread if you'd like to know what real one's look like and how they've changed through the years. I'd really like to hear what you find on your cars. Especially if you think your AC compressor bracket set-up is original to your car.

Thanks Everybody,
Mike