71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

[Joe L.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Back in February of 2009, Joe posted this in a thread test asking about front pipes on LT-1 for 70, 71 and/or 72. I can’t figured out the exact year, if it applied to all three.

”Yes, these are GM #3913895, left side, and GM #3877210, right side. They were replaced by GM #334940 and GM #334926, respectively, in mid-1973. The latter were the forward pipes used in PRODUCTION for 1973-74 2-1/2" small block exhaust and also the ones with the “welded” rather than "swaged" reduction section to the manifold flange.”

Does this mean that some versions of GM 334926 had a swaged reduction from 2-1/2” to 2” and some version of 334926 have a welded reduction?

And which version is shown in Mick’s photo? I would have thought a swaged version would not have had such a step-change in diameter, which made me think the one in Mick’s photo is welded.

Gary

Gary------


I believe I "mis-spoke" in that earlier post. I think that the original 2-1/2" forward pipes were the ones with the welded transition section and the later with the "swaged" transition. Either that or that either set of pipes were manufactured both ways.

[Terry M.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Gary------


I believe I "mis-spoke" in that earlier post. I think that the original 2-1/2" forward pipes were the ones with the welded transition section and the later with the "swaged" transition. Either that or that either set of pipes were manufactured both ways.

Joe
My early 1970 LT1 has swagged front pipes (still on the car). All 1971 $1972 LT1s I have judged to be original have had swagged pipes as well. The real way to tell original Front pipes is to have them off the car and feel their weight look dual pipes at the back end, and look for the stamped part number at the connection between the front and rear pipes. This is, of course, impossible to accomplish during judging.

[Gary B.]

[Terry M.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

The example in Mick D's photo is swagged.

[Gary B.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Thanks Terry.

Gary

[Edward J.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Years ago I brought a Gardner system for my 72 L48 car, and during judging the muffler seam was noted as having crimped seam on the wrong side, not sure if he ever corrected this. Maybe Gary can comment on, I am not sure if Gary touched base on this? Just something to keep in Mind if your going to spend time trying to recreate some close to original.

[Mick D.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Just as a followup folks. It's not often I find car online that looks to have factory exhaust equipment (all the LT-1's on Bat have a rear section without bend), and I've never seen one in person. This 1970 LT-1 car --looks-- to have a factory exhaust (maybe even shocks) , it had 3000 miles when it was sold, but who knows. Anyway, I'm curious what you make of it, the tips are replacement for sure, but the rest does look like what y'all have described above. The (sold) listing is here

1970-chevrolet-corvette-coupe.jpg
1970-chevrolet-corvette-coupe (3).jpg1970-chevrolet-corvette-coupe (1).jpg

[Terry M.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Just as a followup folks. It's not often I find car online that looks to have factory exhaust equipment (all the LT-1's on Bat have a rear section without bend), and I've never seen one in person. This 1970 LT-1 car --looks-- to have a factory exhaust (maybe even shocks) , it had 3000 miles when it was sold, but who knows. Anyway, I'm curious what you make of it, the tips are replacement for sure, but the rest does look like what y'all have described above. The (sold) listing is here

[ATTACH=CONFIG]116849[/ATTACH]
[ATTACH=CONFIG]116850[/ATTACH][ATTACH=CONFIG]116851[/ATTACH]

You can never trust the internet for color or finish and I have just had eye surgery to make it worse -- but that looks like aluminized finish to me. Just my deuce centavos.

[Gary B.]

[Terry M.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

That is not the original finish on the oil pan. While that is not the subject of this thread, it would lead me to question thr originality of the rest of what we are looking at. Now we are up to quarto centavos

[Dave S.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

That is not the original finish on the oil pan. While that is not the subject of this thread, it would lead me to question thr originality of the rest of what we are looking at. Now we are up to quarto centavos

Thst is not original exhaust. Finish does not match any 50+ year old pipes. Another giveaway is the lack of original exhaust tips. Just another internet story.

[Joe L.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Terry, Dave, and Gary------


I totally agree. There is NO WAY that's an original exhaust system as it's definitely aluminized. No original Corvette system of the period was aluminized. Likely, this is a Corvette Central aluminized system. Those are great exhaust systems but, of course, not original.

[Joe L.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Hey Mark, correct they are swaged from 2" out to 2.5" shortly after they exit the manifold.

This picture below is from an EBay advertisement which stated

"NOS Front Exhaust Pipe for 1966-1967 Corvette - P/N 334926 - Right Passenger"

[ATTACH=CONFIG]116738[/ATTACH]

It seemed to have a swage aswell, which is what started me down the path of - 'which other cars have this part', Joe seems to have cleared it up for me above. Prior to this, I did not realize the 'special' LT-1 exhaust parts also existed on other non-LT1 cars back to the sixties.

Mick-------


I'm totally confused on this small block forward pipe thing now. This pipe does not look like the transition configuration of either the welded style or "swaged" style that I'm familiar with. The welded style I'm familiar with has an obvious weld bead and the "swaged" style has a much more "tapered" appearance.

It would be VERY interesting if folks with 1966-72 small blocks with 2-1/2" exhaust could report on or, better yet, post photos of their forward exhaust pipes transition section. It would also be VERY interesting if folks with 1973-75 L-82 could do the same.

[Mick D.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Thanks for your responses gentlemen, I was wondering about the color. Another theory debunked. I'm learning more.

Terry, Dave, and Gary------


I totally agree. There is NO WAY that's an original exhaust system as it's definitely aluminized. No original Corvette system of the period was aluminized. Likely, this is a Corvette Central aluminized system. Those are great exhaust systems but, of course, not original.

[Mick D.]

Re: 71 LT-1 Exhaust same as Service Replacements for 67-68 and 71' 454?

Joe, I am also confused, so I am glad it is not just me . I actually did think that it didn't look swaged myself, but had not seen enough parts to know. If it is one piece, it seems to have been squashed rather than 'pulled' like what I am used to seeing on LT-1s. Here is the link to the part. It does seem to have a GM sticker on it. Maybe the extra photos will give you more clues.

Mick-------


I'm totally confused on this small block forward pipe thing now. This pipe does not look like the transition configuration of either the welded style or "swaged" style that I'm familiar with. The welded style I'm familiar with has an obvious weld bead and the "swaged" style has a much more "tapered" appearance.

It would be VERY interesting if folks with 1966-72 small blocks with 2-1/2" exhaust could report on or, better yet, post photos of their forward exhaust pipes transition section. It would also be VERY interesting if folks with 1973-75 L-82 could do the same.