62-65 2 1/2" exh. manifolds

[John H.]

Re: 62-65 2 1/2" exh. manifolds

One Corvette parts supplier advertises that they "bought the original GM molds",of which I've only seen a few of,but certainly don't look like the ones that came on cars(don't recall if or what core #s they had)Which GM molds were those?

Sounds like hype to me; the "molds" were sand, after it was packed around the "pattern". Then the mold (upper half was the "cope" and the lower half was the "drag") was separated, the iron or stainless steel numbered pattern was removed, baked refractory sand "cores" were placed in the mold cavity (they formed the hollow inner passages), the mold upper and lower halves were re-joined, and the casting was poured.

After cooling, the upper and lower halves were separated, and the casting and mold sand (and internal cores) were separated on the "shake-out" table, at which time the "mold" was destroyed - it was just sand.

Patterns wore due to the constant abrasive action of creating the sand molds, and eventually required repair or replacement; they came out of the molding line once a day anyway to have the brass date tags changed by foundry service workers.

[Tom P.]

Re: 62-65 2 1/2" exh. manifolds

Tom, was that a GM Manufactured service part or from the "approved reproduction" parts line? How was it boxed and dated?

OK Bill,
Here is some of what I have.
This is a 563 dated Apr 17, 95 and the box it came in with a Jun 17, 95 date.




This is the top of that same manifold where a grinder had been used to remove the parting line. I smoothed down the grinding marks somewhat then blasted it to reduce the "ugliness".


This is another 563 with NO date, but a logo that I've never seen on any other manifold.
And the box it came in with a Feb 28, 01 date.




This is the top of that same manifold. The grinding marks are not so bad, so I didn't try to smooth it out any.


This is an original 942 and the untouched parting line on top.







This is a 902 (3814970 part #), the box it came in, dated Sep 21, 01 and the grinding marks on top.






And once again, here are original (actually, recent service parts) 901 and 902 manifolds from Chev parts dept comparred to the Chinese repo manifolds (Chinese on top in each picture).




And here is a plain (942 style) manifold that I've made using the 563 manifold.

[E S.]

Re: 62-65 2 1/2" exh. manifolds

William-You mentioned finished part numbers-I'm focused on the 902 manifold (without the choke tube holes) because they are so xxxn hard to find.I have a corvette p&a catalog (1973) that lists A 902 as part # 3814970. I assume that the 3814970 is a 902 with the choke tube holes,since it would work for either carb or fi.If that is the case-what would be the part number be for a 902 without the choke tube holes?
Seems that some have same part # as casting #
Thanks again-E.J.

[William C.]

Re: 62-65 2 1/2" exh. manifolds

Yes, that is the same junk that GM parts has been selling for quite a few years. It has significant problems from a judging perspective, in fact the Paragon items of the last few years are likely a better representation of the originals..

[William C.]

Re: 62-65 2 1/2" exh. manifolds

I don't believe that item was ever sold as a service unit, and I've been buying them since about 72 or so.

[Tom P.]

Re: 62-65 2 1/2" exh. manifolds

William-You mentioned finished part numbers-I'm focused on the 902 manifold (without the choke tube holes) because they are so xxxn hard to find.I have a corvette p&a catalog (1973) that lists A 902 as part # 3814970. I assume that the 3814970 is a 902 with the choke tube holes,since it would work for either carb or fi.If that is the case-what would be the part number be for a 902 without the choke tube holes?
Seems that some have same part # as casting #
Thanks again-E.J.

EJ,
The only 2.5in manifolds that I've ever seen which had the same part number on the box as was cast on the manifold was the 901 and 563 versions.
All the 902 versions that I'm aware of carried the 970 part number.
Furthermore, I've NEVER seen a 942 manifold without the choke tube.
When the 942 was installed on the RIGHT side, it was for a carb engine that needed the choke tube.
When installed on the LEFT, it was on an FI engine which needed a choke tube.
The 62 FI engines had an elec choke, thus they did not need a choke tube--------------BUT, I've never seen a 942 on a 62 engine.

[E S.]

Re: 62-65 2 1/2" exh. manifolds

EJ,
The only 2.5in manifolds that I've ever seen which had the same part number on the box as was cast on the manifold was the 901 and 563 versions.
All the 902 versions that I'm aware of carried the 970 part number.
Furthermore, I've NEVER seen a 942 manifold without the choke tube.
When the 942 was installed on the RIGHT side, it was for a carb engine that needed the choke tube.
When installed on the LEFT, it was on an FI engine which needed a choke tube.
The 62 FI engines had an elec choke, thus they did not need a choke tube--------------BUT, I've never seen a 942 on a 62 engine.

Tom -I fully agree with everything you have said-
Where did the 942 without a choke tube and on a 62 engine come from?
I was trying to find out the finished part #'s for both 902's-E.J.

[Tom P.]

Re: 62-65 2 1/2" exh. manifolds

Tom -I fully agree with everything you have said-
Where did the 942 without a choke tube and on a 62 engine come from?
I was trying to find out the finished part #'s for both 902's-E.J.

EJ,
As I understand, the 942 was NOT used on a 62 Corvette. I cannot speak with such certainty about 62 pass cars. TO THE BEST OF MY KNOWLEDGE, ONLY 901 and 902 manifolds were used on 62 Vettes (300-340-360 engines). BUUUUUUUUUUUUUT, IF a 942 did get used on a 62 pass car, then it DID have the choke heat riser tube installed, because it would have ONLY been used on the RIGHT side of the engine and 62 pass car still had carbs with chokes using exhaust heat. The 942 was NOT used on the left side of a 62 pass car because ALL 62 pass cars had the gen mounted on the left side--------------which required a 901 manifold.
Soooooooooooo, back to my original comment. The 62 Vettes (at least none that I'm aware of) never got a 942 manifold.
The ONLY part number that I've EVER seen for a 902 manifold is 3814970--------------------WITH or WITHOUT the choke heat riser tube.
That's the best info I can give you.

As I've shown earlier, whenever I have needed a 942 type manifold WITHOUT a choke tube, I have made it from a 563, OR, had the upper-lower holes welded on an original 942 manifold (the machine shop that I use can plasma spray weld cast iron).

[Michael H.]

Re: 62-65 2 1/2" exh. manifolds

I don't believe that item was ever sold as a service unit, and I've been buying them since about 72 or so.

I agree with Bill. The undrilled right side manifold for 62-65 FI cars without the choke hole and tube was never available through service. It was a Flint engine assy part only and no part number existed outside of the original paperwork used at Flint. The number never was in the service parts system.

The drilled manifold, identical in all other ways, was the only one available for service/over the counter replacement.

[James G.]

Re: 62-65 2 1/2" exh. manifolds

I agree with Bill. The undrilled right side manifold for 62-65 FI cars without the choke hole and tube was never available through service. It was a Flint engine assy part only and no part number existed outside of the original paperwork used at Flint. The number never was in the service parts system.

The drilled manifold, identical in all other ways, was the only one available for service/over the counter replacement.

I AGREE. And that is why if you see an original on eBay or at a swap meet, they are $2500 and up.

[E S.]

Re: 62-65 2 1/2" exh. manifolds

Tom- Apparently there has been a mis-understanding.I don't know who started talking about "942's w/o choke holes",and "942's on 62 corvettes"-but it certainly was'nt me.-That would be laughable,don't you think?
After owning several original 62-65 corvettes since 1967 with the high perf. 327 (63 340, 65 350, 65 375, current 62 360)I do feel that I am aware of the 7 digit GM casting numbers as well as the various applications in which the 901,902,942,and 563 manifolds were used.
I posted on this forum simply to learn more about these manifolds- namely- what do the various "core" numbers mean,? and also,do all 4 manifolds have "finished part #'s" to go along with their casting numbers?
Thanks to you,Terry,Wayne,Michael,William,and John-I have learned more about this subject.I have always enjoyed sharing facts/data/opinions/stories/etc. about the corvette.
Thanks again.

[Tom P.]

Re: 62-65 2 1/2" exh. manifolds

EJ,
I actually provided more info than what was originally asked for. BUT, as I have often had questions which went beyond the original question which was asked, I thought there may be others who also would like to have some additional info regarding use and availability of 2.5in manifolds, so, I included more.
I have been an NCRS member for nearly 30yrs, and I am FULLY aware of the direction and purpose of NCRS. BUT I AM NOT, repeat, AM NOT a numbers/absolute correctness freak! I THOROUGHLY admire and apperciate an immaculately correct restoration. But that's not my objective. My objective is to have not only a VERY nice looking car, but also one that will beat the pants off of most anything else. To me, the 56-57 is the absolute ultimate classic Vette. BUUUUUUUUUUT, for me, a totally correct 265 or 283 is NOT the absolute ultimate performance power plant. That's why my 56 has a killer SB400!
Also, on that much displacement, a Rochester FI unit will NOT allow it to perform to its full potential, but I am also obcessed with FI, so, I've compromised and attempted to merge the best of both (or all three). I have gone to great lengths (and money) into making the SB400 resemble a 57 FI 283-------------------not to particularly fool anyone, but because from my viewpoint, that was the coolest looking FI engine in the history of Rochester FI!