[Rocky Rotella]

I'm trying to confirm the original part number for the 70-73 Firebird muffler.

I've got two different part numbers from vintage Master Parts Catalogs, but am looking for the actual number embossed on the case. Does anyone have an original car or muffler they can refer to?

[4birds]

Rocky, here are a couple pics of an original dual in/dual out off a 73 Formula.

[Transamric]

Initially went to the 1970 & 1971 Firebird Product Information Manual to look at the number, but remembered that the assembly line muffler already had the tailpipes welded to it, so that number would be for the assembly.
The May 1, 1970 Pontiac MPC shows in Grp. 3.701, a 481723 muffler for all '70-71 V-8 4bbl applications. But since this was a muffler only not as assembly line installed, would we consider that only a Service Replacement number?
Then the March 1973 MPC shows as 4birds pictured above; '70-73 all Formula & Trans Am except '73 SD455 was 494965.
My opinion on this is that the 494965 was the superceded part for the 481723. In general, no part numbers or casting numbers would have been assigned a 494xxx number until into the 1973 model year. This does jive with 4birds mention that his muffler pic is from a '73.
495335 was an even later service replacement muffler for this application. I've seen these dated 1976 & up.

[Rocky Rotella]

Thanks 4birds!

Ric, I think you're probably pretty close. Do you have any original mufflers by chance?

[Transamric]

Don't think I have any before the 495 series. I'll double check when I get home tonight.

[giles]

Originally Posted by Transamric

But since this was a muffler only not as assembly line installed, would we consider that only a Service Replacement number?

Ric, you are right...production part numbers and service numbers can be the same but often times are not. In the case of the welded assembly, in production there would have been part numbers for the tailpipes, for the muffler and for the welded assembly. These numbers are assigned prior to start-of-production (and sometimes changed / super ceded after).
When Parts Div. creates service parts they will typically take the production part and number. In the case of this muffler they may have found the service part required different inlet and outlet flanges to allow for repair in the field (clamps rather than welding) so a unique part and part number would have been released for service.
Parts Div would also "commonize" similar parts where possible, so several production parts would be superceded by a single service part. 70-81 Fenders are a really good example of this substitution that most are familiar with.

[Transamric]

Checked what I have for mufflers & there's nothing before the 495335 dated 12/76. Noticed that this muffler is stamped with a GM logo rather than Oldberg. Do we know when GM switched to their own mufflers?
I do also have a NOS single exhaust muffler dated 3/73 as a backup for my '72 Esprit. It is an Oldberg.

Attached a pic of the muffler recently removed from my '70 TA. Replacing it with one from Classic. I guess only two muffler changes in 44 years isn't too bad.

[grrrrregg!!!]

Originally Posted by 4birds

Rocky, here are a couple pics of an original dual in/dual out off a 73 Formula.

Crawling around under my newly acquired 70 Trans Am and while looking at the exhaust I noticed the GM mark. My mufflers script reads like 4birds but with these changes. Any chance this is oe

INLET

OLDBERG

5 70 A

GM

481248

this car has been in dry storage since 82

thanks

[Formulabruce]

These Cross flow mufflers were a J.R.Hall design . He worked for Oldberg Exhaust in Michigan in the 60's, this was in New Grand Haven ?. I remember seeing an Oldberg tag on a old muffler for a 72 Camaro. GM bought the patents for some and had a FEW people make them for them through the 70's. I believe some had AC on the boxes, which distributed parts ( AC Spark plug company) I Think its possible that Arvin, Walker and maremount were involved in later units. Arvin moved from Canada to Indiana for muffler work around 1970.

[grrrrregg!!!]

[QUOTE=grrrrregg!!!;5388043]Crawling around under my newly acquired 70 Trans Am and while looking at the exhaust I noticed the GM mark. My mufflers script reads like 4birds but with these changes. Any chance this is oe

INLET

OLDBERG

5 70 A

GM

481248

this car has been in dry storage since 82
photo of muffler

[Formulabruce]

Nice pic look correct to me!!