Intake #'s

[Gary J.]

I have an intake that has the part # 3866948---GM 2-----T---- on it. What is the application for it. What does GM 2 and the T stand for? Thanks to all who answers.

Gary Jaynes
#3503

[Terry D.]

Re: Intake #'s

According to the Corvette Spec Guide it is a cast iron manifold that fits 1966 and 1967 427ci 390hp. It also was used on 65, 66, 67, 396 and 427 passenger and Chevelle's. Someone else will have to let you know about the other numbers.
Terry

[Joe L.]

Re: Intake #'s

Terry and Gary------

The "GM 2" is the mold or pattern number. The "T" represents the Tonawanda, NY foundry where all Corvette big block castings were made until 1984.

[Gary J.]

Then why

Would there be two molds or pattern numbers?

Gary

[John H.]

Re: Then why

There were multiple patterns used to make the sand molds the intakes were poured in; each individual pattern had its own number for traceability reasons. The pattern also carried the casting date insert, which was changed each day.

[Terry M.]

Re: Then why

I am told the multiple patterns John refers to could be as many as a dozen, or as few as one, depending on the complexity and production run of the piece to be cast. Mark Gorney is the resident expert (of course. John is as well -- no intent to denigrate John), since Mark works at -- what is it called now? -- Saginaw Metal Castings IIRC. The old Saginaw Foundry which back in the day supplied all the iron castings to the Flint Engine and Flint Motor plants.

[Joe L.]

Re: Then why

Gary-----

One other thing I'll add is that during the 66-67 period there were a lot of these manifolds manufactured. Therefore, it was necessary to have multiple molds or patterns so that enough could be produced. There is no "correct" mold or pattern number for any particular car, though. The number which was found on any particular car was completely random (assuming that there was more than 1 mold or pattern used). The only way to know what number was used on a particular car is to have the known-original cast part from that car.

For example, the mold or pattern number for the GM #3927184 manifold originally installed on my 1969 300hp 350 was "GM 5". I know that's the original manifold since I've owned the car since new. Other engines produced that year likely had many different other numbers, though, and there's no way to know what came with any particular car except as described above.

[Mark G.]

[Joe L.]

Re: Because

Mark----

As usual, very interesting (especially, for a guy that loves castings, like me). I think that I have seen some of these "T-suffix" castings on small blocks. What did the "T" denote on these castings? I've noticed that the format on the Tonawanda castings is different. For those, it's usually "GM T" followed by the number. Tonawanda forgings (from the old forge plant located there) often have the same format, too.

When you mentioned "nodular iron" I assume that you are referring to a particular foundry. Is that the other Saginaw Foundry (old CF headquarters), the long-closed foundry with the "tear drop" water tank that's "across-the-street" from Gray Iron, the nodular iron foundry at Defiance, OH, or the old Danville (Tilton) IL nodular foundry?

I've never been able to discern any foundry ID marks for Saginaw Gray Iron or Defiance, OH gray iron. Do you know if any were ever used? Tonawanda typically uses the "T", St. Catherines usually used a "K", and Danville used a "D", but I've never been able to come up with any for Saginaw or Defiance gray iron foundries.

[Mark G.]