C3 Exhaust Manifold?

[Ed Schmitt]

I have a '72 small block with a cracked exhaust manifold. I'm trying to match the existing manifold. I can find the correct casting number and close date code but what about the number below GM? I think this is the mold number. Mine says RH5. Is this linked to the date? I found a set that is RH13. Does this mean this is from the wrong year?

Thanks, Ed

[Harmon C.]

Re: C3 Exhaust Manifold?

Ed
I think you answered your question it is a mold number not a date.
Lyle

[Ed Schmitt]

Re: C3 Exhaust Manifold?

Lyle: Sorry if I wasn't clear. My question is: Is the mold number tied or related in anyway to the date of manufacture. For example if I have RM5 and the one I found is RH13, did RH13 exist in 1972 or was this only on cars newer then mine.

Thanks, Ed

[Joe L.]

Re: C3 Exhaust Manifold?

Ed------

It's POSSIBLE that pattern numbers were, in some way, related to date. For example, it's POSSIBLE that certain pattern numbers were "retired" for whatever reason and weren't being used to produce parts as of a certain year of manufacture. By the same token, it's POSSIBLE that certain pattern numbers didn't exist yet at the time that certain dated parts were manufactured. If so, though, no one that I know of is able to document that and, consequently, the issue is moot. I don't think that anyone ever will be able to document such in any really meaningful way that could be used in the judging process. So, the bottom line is I wouldn't be the least bit concerned about pattern numbers. The fact is simple: if you have a cast part that's dated correctly for the car, whatever pattern number is on it was used to produce a part that could have been installed on the car. Period.

In the case of parts without casting dates, my "theory" as described above might come into play. However, as I mentioned, I don't think anyone will ever be able to document it.

[Ed Schmitt]

Re: C3 Exhaust Manifold?

Joe, Thanks. That's just what I was looking for.

Regards, Ed

[Harmon C.]

Re: C3 Exhaust Manifold?

Ed
If your 72 had 3932461 exhaust manifolds they were made in many different configurations. I know of at least three styles that have four AIR holes. Their is a square block on them that changes in size over the years and a boss for what looks like a carburetor tube on others. I think a study on this part number alone would find many little known facts.
If the ones you found are the exact same shape I would say you are ok with that mold number. If a judge could see a configuration difference I would keep looking.

Lyle

[Harmon C.]

Re: C3 Exhaust Manifold?

Joe
I think the small block exhaust manifolds only being dated month and day makes the year or years they are correct for not an easy job for a judge who has only seen a small sample.

Lyle

[Kenneth B.]

Re: C3 Exhaust Manifold?

You are exactly right. I own a pattern shop. If there were 6 patterns on a mold plate they would # 1 to 6. Most of the auto castings had more than one set of tooling & as the old patterns wore out the pattern #'s would continue change.Usually if there was a slight change in the casting shape, most of the time the part # did not change.

KEN

[Bob E.]

Re: C3 Exhaust Manifold?

Ed,
I just looked at my '72 convertible. Exhaust manifolds are Both #3932461 with a mold # of RH14 on both. The car is very original, Ihave no doubts that they are original. I did notice that the JM says manifold #3932461 on both sides is late '72 although mine is #4500 which I think is a late September car.

[Ed Schmitt]

Re: C3 Exhaust Manifold?

Bob, Thanks, that's good to know. My car is a very late '72 was made on second to the last day of production for the model year. It had cast #3932461 on both sides.

Thanks, Ed