'72 Exh Manifolds

[Chris Baird]

I'm trying to find the correct exhaust manifolds for my '72. I have seen 3932461 manifolds with large and small cast size numbers. The large ones are around 1/4 inch tall, and the small numbers are 1/8 inch tall. Did they switch cast number sizes at a certain year? Does it matter what size they are in judging? I believe the manifolds do not have a year cast into them. Is this correct? Thanks, Chris

[Joe L.]

Re: '72 Exh Manifolds

Chris------

I don't know if the manifold casting number size difference is a function of when the manifolds were produced or whether it's just one of the peculiarities of one mold versus another mold. A lot of these manifolds were produced since they were also used quite liberally in trucks. Consequently, a lot of different molds likely existed. Plus, I expect that they were cast at both Saginaw, MI and Tonawanda, NY.

In any event, I think that these manifolds used for Corvettes and produced at Saginaw are dated in the typical GM Saginaw foundry casting procedure of alpha-character for month, space, one or two digits for day, space, then last digit of the year. If I recall, the date is on the side of the manifold which is toward the engine and is difficult, if not impossible, to see with the manifolds installed. Consequently, I don't think that the dates are judged. However, you should certainly be able to tell if a particular manifold was produced during the "correct" time for your car. That would supercede and render moot the casting number character size issue.

One thing to keeep in mind, though, is this: the GM #3932461 casting manifold was produced for a LONG time. I think that manufacture of this piece began about 1968 and continued at least through 1979, and possibly later. So, it's possible that manifolds produced in 1978 or 79 could be "mistaken" for those produced in 1968 or 69. However, if I recall correctly, whenever Saginaw had a production period for a casting that exceeded 9 years, they would start to use the "two digit" system for the year at the 10th year. This doesn't happen very often, though, since most casting part numbers don't stay in PRODUCTION that long.

[Terry M.]

Re: '72 Exh Manifolds *TL*

The date on Saginaw cast small block exhaust manifolds used in 1968 to 1972 is letter for the month (typical cast month alpha designators A through L) and one or two numbers for the day of the month. No year is indicated during this period.