Joe L. - Exhaust Manifold Part Numbers Please

[Joe C.]

Joe,

Please provide the part numbers for 1965 327/365 HP, both left and right sides, with A/C and without A/C. There is something strange about the TIM&JG, which I need help with.

Thanks in advance.

Joe

[Joe L.]

Re: Joe L. - Exhaust Manifold Part Numbers Please

Joe-----

Part of the confusion may involve the fact that exhaust manifold PART numbers may not be the same as CASTING numbers. However, I'll provide both:

left side w/C-60---CASTING=3846563----PART #=3846563

right side w/C-60---CASTING=3797942----PART #=unknown; PRODUCTION-only part

left side w/o C-60---CASTING=3846563----PART #=3846563 (note 1)

right side w/o C-60---CASTING=3797902----PART #=3814970

Note 1: While it may seem unlikely that this 3846563 manifold was used for the right side of non-C-60 applications with 2-1/2" exhaust, I believe that it may actually have been used. If so, though, I don't know why. This manifold has the forward-facing bosses for alternator mounting which is unused for the non-C-60 1965 applications (which use right side alternator mounting). It would seem like the 3797942 would have been the more logical choice, since this manifold had no bosses for generator mounting and was used for right side C-60 apps.

[Wayne M.]

Re: Joe L. - Exhaust Manifold Part Numbers Please

Joe -- I believe the parts # table in '65 TM & JG 5th edition is correct (w/small typo on LH manifold base motor w/AC --- last 3 digits should read ...559).

All 2_1/2" manifold engines are correcly shown. The blank cells in the table mean the same part #'s apply from the line above. The LH manifold is always 3846563 EXCEPT for fuel injection, which uses the manifold 3797942 in that location, which is the RIGHT HAND manifold for 2_1/2" engines with air conditioning. This leaves the RH manifold #3797902 for 300 (4sp), 350 and 365hp engines without A/C.

Hope this is of help.

[Joe C.]

Re: Joe L. - Exhaust Manifold Part Numbers Please

Joe,

The conundrum involves the 327/365 without air conditioning, versus the 327/375 (never available with air conditioning) engine. Both of these engines have the alternator mounted on the right (pass) side, correct?
Specifically, why would the 327/375 engine use a plain (942)left side manifold, and the 327/365 engine, without A/C, use a bossed (563) manifold for both A/C and non-A/C use. Why would the 327/365 without air conditioning not use the "942" left side manifold.

Joe

[Joe L.]

Re: Joe L. - Exhaust Manifold Part Numbers Please

Joe-----

That's PRECISELY my question. Since the "un-bossed" manifold (942) was available at the time and, even, used for the right side of C-60 cars, I don't understand why it was not used for the left side of non-C-60 2-1/2" exhaust cars.

Of course, part of the reason that the 942 was used for the left side of C-60 cars may be that any sort of boss on that side would have created interference with the compressor mounting. Still, the same manifold could have been used for the left side for non C-60. Plus, it would have represented a cost savings---extra machining operations had to be performed on the 563 manifold that would not have been required on the 942.

One curious observation, though, is that, as I described in my previous post, the GM CASTING #3797942 manifold was NEVER available in SERVICE. For SERVICE, the GM #3846563 manifold was always specified as the replacement for ALL 1965 applications with 2-1/2" exhaust. By the way, the GM PART #3814970 (CASTING 3797902) was always specified as the SERVICE manifold for the right side of ALL 1965 2-1/2" applications, including C-60. This manifold has the side-mounted alternator bracket on the front end when mounted on the right side of the engine. So, apparently, the manifold bracket will not interfere with the A/C compressor or this manifold could not have been used for SERVICE of all applications.

I wonder if the GM #3846563 manifolds seen on the left side of non-C-60 1965 Corvettes with 2-1/2" exhaust are really SERVICE manifolds which have come to be accepted as original? There are no dates on any of these 2-1/2" manifolds (except, perhaps, those made for MUCH, MUCH later SERVICE), so one could not infer originality via "dates".

[Joe C.]

Re: Joe L. - Exhaust Manifold Part Numbers Please

Joe,

I have been trying to find out about the "942" manifolds on the left side of non C-60 cars w/ 2 1/2" exhaust, but have had no luck. All that I have seen/asked about have the "563" on the left side, per the TIM&JG. That was my thought, exactly, that these cars LOGICALLY SHOULD have originally used a plain "942" manifold on the left side. I suppose that this is just another mystery that may never be solved...........stranger things than this were done "back in the day". The only other possibility that makes any sense is that Flint had very few "942" manifolds in inventory, and, anticipating no future need for them, decided to use their (probably) large inventory of "563's" as an all-purpose part. Once the remaining inventory of "942's" were exhausted, they were no longer produced. This, of course makes any genuine "942" manifold WITH THE CORRECT CASTING NUMBER extremely rare today. It is quite possible to convert a "563" manifold into a dead-ringer "942" manifold, EXCEPT for the casting number...........well, that can probably be done, too, using a special heat resistant epoxy, and then ceramic coated.

Joe

[Joe C.]

Re: Joe L. - Exhaust Manifold Part Numbers Please

Wayne,

Thanks for the response, and see my discussion with Joe, here, for more thoughts on this. The usage table shown in the TIM&JG is illogical, but stranger things than this were done back in the "good old days". There may have been a good reason for the unusual application, such as inventory, and anticipated phase-out of the "942".
Joe

[Mark G.]

[Wayne M.]

Don't forget the choke heat tube

I agree that cosmetically, the 942 (which has a choke heat tube) would have done for the left-hand manifolds for OTHER than fuel injected cars (in which case the choke heat tube was NOT required), but I suppose that the bean-counters decided that 3846563 (with the flanged forward bosses for the alternator, even though not used at all on non-A/C cars) was the economic left-hand manifold choice.

[Joe L.]

Re: Don't forget the choke heat tube

Wayne and Joe-----

Yes, in a way, I don't know why I questioned it. The practice of using manifolds with unused alternator brackets was already well-established by 1965. Both C1 and earlier C2 did generally use manifolds on one side which had an unused bracket.

It's always surprised me, though. The "unused bracket syndrome" is something that the factory usually tries real hard to stay away from. For one thing, it gives a very unfinished, "non-factory" appearance, ESPECIALLY when the unused bracket is in a very prominent location (like the exhaust manifolds). Plus, the "unused bracket" raises owner questions like "...what did the factory leave off there...".

It's especially surprising when they have the non-bracket manifolds already in the "parts bin"; no need to create them from scratch; they already exist. Plus, they should be cheaper to produce---less cast iron and less machining operations.

In any event, the practice of the "unused exhaust manifold bracket" ended, for good, after 1965. From that time on, there were no "unused brackets" on Corvette exhaust manifolds.