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

[Gary B.]

^st car has those pipes. Starting sometime between then and May 6^th

[Mick D.]

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

Great write up Gary, I see there is an awful lot to think about when recreating this exhaust system. Thank you for taking the time out of your day to help me out.

Just to confirm what I'm reading - If i find ANY sweged exhaust (like the one I took a picture of above) w/ double wall - it's basically an 'assembly line' part, because everything out of SERVICE was welded and/or single wall, no matter the year.

Not to show any disrespect to anybody, but after looking at few hundred cars... What I know about 68-72 exhaust. Others can fill in what I missed.

All 68’s have 2-1/2” exhaust. 68 was the last year for N-11 mufflers. Small block exhaust manifolds were 2” outlets, so for the front exhaust, GM welded 2” pipes to 2-1/2” pipes. They were not swedged. Early 68 pipes from the transmission crossmember to the muffler were shaped like mid-year pipes, no ripples. Kind of a double “D” shape. My 68 L71 April 1^st car has those pipes. Starting sometime between then and May 6^th, they went with flattened pipes (top and bottom), with fine ripples in all the bends, all the way through 1972.

All 69’s had 2” exhaust. Even big blocks and side pipes. Yes, even L-88’s.

In 1970, through 1972, base motor cars used 2” exhaust. All LT-1’s and 454’s used 2-1/2” exhaust. The front pipes were swaged from 2-1/2” to 2” to fit the 2” exhaust manifolds (small block). Service and over the counter were all welded, not swedged. LT-1 and 454 rear pipes and mufflers looked the same.

The center pipes, from the front pipes to the mufflers, were 2-1/2”, with fine ripples in all the bends, even just before where the pipe enters the mufflers. Original mufflers only had one mount for the rear hanger. Over the counter mufflers used 2-hanges, one for C-2’s and one for C-3’s. They also had a pipe (elbow) welded into the front of the muffler, designed to be used with a muffler clamp. Common muffler between C2 and C3. The farthest rear pipe that exits the muffler, that the tips slide on to, was welded inside the muffler. Repo’s, they are welded on the outside.

To the best of my knowledge, GM never offered the center pipes that ran from the front pipes to the front of the mufflers for C3. See some for C2’s occasionally. I believe GM only offered through service, missing the elbow just before the muffler.

Walker made the pipes for GM, at least through 1972. Over the counter parts stores (NAPA as an example) sold Walker pipes. They look the same as what GM sold. Front pipes are welded, not swedged. Rear pipes are missing the final elbow. Muffles have the elbow, but without the ripples.

Very late 72’s, I think either June or July, showed up with Arvin pipes. The ripples are much coarser than the Walker pipes. Gardner exhaust simulates Arvin pipes. Very late 72’s, the front head pipes started with wrinkles, the fine Walker wrinkles.

All original pipes are double wall pipes, a pipe inside a pipe. All over the counter pipes are single wall. Some GM over the counter pipes could be bought early on, double wall. Over the years, I have found a few.

Factory configuration of pipes and mufflers (one piece) were only available from the assembly line. Over the counter is different. Can you make them look correct? Yes, with a lot of work.

If you can find a 70-72 Parts book, that is what I would look for in numbers. From my October 1970 book…
Front header pipes 3877210 RH, 3913895 LH. Rear pipes, 3931829, 3931830. Exhaust tips 3974659, 3974660

Happy hunting

Gary Bosselman
68-69 Manual Coordinator
70-72 Manual Coordinator

[Mick D.]

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

I have added some of detail from people in the thread to the attached PDF, it is only a v1, but it will help me easily remember all that I have learned today. There is still room to add more, but it is late

Great write up Gary, I see there is an awful lot to think about when recreating this exhaust system. Thank you for taking the time out of your day to help me out.

Just to confirm what I'm reading - If i find ANY sweged exhaust (like the one I took a picture of above) w/ double wall - it's basically an 'assembly line' part, because everything out of SERVICE was welded and/or single wall, no matter the year.

[Gary B.]

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

Your photo and comments look correct.
Gb

[Joe L.]

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

Not to show any disrespect to anybody, but after looking at few hundred cars... What I know about 68-72 exhaust. Others can fill in what I missed.

All 68’s have 2-1/2” exhaust. 68 was the last year for N-11 mufflers. Small block exhaust manifolds were 2” outlets, so for the front exhaust, GM welded 2” pipes to 2-1/2” pipes. They were not swedged. Early 68 pipes from the transmission crossmember to the muffler were shaped like mid-year pipes, no ripples. Kind of a double “D” shape. My 68 L71 April 1^st car has those pipes. Starting sometime between then and May 6^th, they went with flattened pipes (top and bottom), with fine ripples in all the bends, all the way through 1972.

All 69’s had 2” exhaust. Even big blocks and side pipes. Yes, even L-88’s.

In 1970, through 1972, base motor cars used 2” exhaust. All LT-1’s and 454’s used 2-1/2” exhaust. The front pipes were swaged from 2-1/2” to 2” to fit the 2” exhaust manifolds (small block). Service and over the counter were all welded, not swedged. LT-1 and 454 rear pipes and mufflers looked the same.

The center pipes, from the front pipes to the mufflers, were 2-1/2”, with fine ripples in all the bends, even just before where the pipe enters the mufflers. Original mufflers only had one mount for the rear hanger. Over the counter mufflers used 2-hanges, one for C-2’s and one for C-3’s. They also had a pipe (elbow) welded into the front of the muffler, designed to be used with a muffler clamp. Common muffler between C2 and C3. The farthest rear pipe that exits the muffler, that the tips slide on to, was welded inside the muffler. Repo’s, they are welded on the outside.

To the best of my knowledge, GM never offered the center pipes that ran from the front pipes to the front of the mufflers for C3. See some for C2’s occasionally. I believe GM only offered through service, missing the elbow just before the muffler.

Walker made the pipes for GM, at least through 1972. Over the counter parts stores (NAPA as an example) sold Walker pipes. They look the same as what GM sold. Front pipes are welded, not swedged. Rear pipes are missing the final elbow. Muffles have the elbow, but without the ripples.

Very late 72’s, I think either June or July, showed up with Arvin pipes. The ripples are much coarser than the Walker pipes. Gardner exhaust simulates Arvin pipes. Very late 72’s, the front head pipes started with wrinkles, the fine Walker wrinkles.

All original pipes are double wall pipes, a pipe inside a pipe. All over the counter pipes are single wall. Some GM over the counter pipes could be bought early on, double wall. Over the years, I have found a few.

Factory configuration of pipes and mufflers (one piece) were only available from the assembly line. Over the counter is different. Can you make them look correct? Yes, with a lot of work.

If you can find a 70-72 Parts book, that is what I would look for in numbers. From my October 1970 book…
Front header pipes 3877210 RH, 3913895 LH. Rear pipes, 3931829, 3931830. Exhaust tips 3974659, 3974660

Happy hunting

Gary Bosselman
68-69 Manual Coordinator
70-72 Manual Coordinator

Gary-------

I need to clear up some things here.

The last 2-1/2" small block exhaust manifold was for 1965. After that, all small blocks with 2-1/2" exhaust required forward pipes with a transition section from the manifold's 2" outlet to 2-1/2"

1968 small blocks with MT used the exact same right side forward pipe as 1966-67, GM #3877210. The left side pipe was different and of GM #3913895. Both of these pipes used a welded transition section. Both of these pipes were exactly the same in PRODUCTION and SERVICE. Both were of double wall construction. As a matter of fact, in this case, if PRODUCTION was double walled, then SERVICE had to be double wall because they were the exact same part PRODUCTION or SERVICE.

As far as the rear pipe and mufflers go, it was like this. In PRODUCTION, the 1968 rear pipes and mufflers, both standard and N-11, were an assembly with the pipes welded directly to the mufflers. These were never available in SERVICE (although such assemblies were available in SERVICE for 1963-67 N-11). In SERVICE, the pipes and mufflers were only available separately. The rear pipes were 7" shorter than the PRODUCTION pipes to allow for connection to SERVICE mufflers which had welded-on curved extensions on the forward side. However, except for the 7" shorter length, the pipes were identical to PRODUCTION. If SERVICE mufflers were installed to original pipes, the pipes had to be commensurately shortened. Both PRODUCTION and SERVICE rear pipes were double-walled. Also, the 1968 427 rear pipes and mufflers. both PRODUCTION and SERVICE, were the same as small block.

The 1968 SERVICE mufflers for standard exhaust, GM #3943385 and 3943386 were the same as PRODUCTION except for the aforementioned forward extension and the fact that they included both the C2 and C3 hanger brackets. These same SERVICE mufflers replaced the C2 2-1/2" mufflers, GM #3820639/40 (1963-64) and 383846535/6 (1964-67). They also replaced the 1968 N-11 SERVICE mufflers, GM #3931803/4. The aforementioned C2 mufflers included only the C2 style hanger bracket and NOT the dual brackets of the GM #3943385/6. The 1968 N-11 SERVICE mufflers I mentioned were the ONLY C3 2-1/2" mufflers that were ever supplied with only C3 hanger brackets. No other 2-1/2" C3 SERVICE mufflers were ever equipped with only C3 hanger brackets.

The 1970-72 LT-1 PRODUCTION exhaust system was EXACTLY the same as the 1968 small block with MT PRODUCTION exhaust systems. The 1970-72 LT-1 SERVICE exhaust system was EXACTLY the same as the 1968 small block SERVICE exhaust system.

In late 1972-early 1973 the 1968 small block and 1970-72 LT-1 SERVICE forward exhaust pipes were replaced by GM #334925 and 334926, These are the same forward pipes used in PRODUCTION and SERVICE for 1973-74 Corvettes with L-82. These are the pipes with the "swaged" transition section from 2" to 2-1/2" and are double-walled. By the way, 1973-74 big block forward pipes were also replaced for PRODUCTION and 66-72 SERVICE by GM #334932 and 334933 about the same time. These pipes are also double walled.

Here's the story on part numbers:

1968 small block (non-N-11) with MT and all 1970-72 LT-1:

forward pipes:

LH GM #3931985 >11/72> 334925 > discontinued w/o supersession 1/93

RH GM #3877210 > 6/73> 334926 > discontinued w/o supersession 11/92

rear pipes:

LH GM #3931829 > discontinued w/o supersession 11/91

RH GM #3931830 > discontinued w/o supersession 8/90

mufflers:

LH GM #3943385 > discontinued w/o supersession 1/93

RH GM #3943386 > discontinued w/o supersession 1/93



I know nothing of any GM supplied SERVICE exhaust pipes, PRODUCTION or SERVICE that were anything but double-walled. I have 2 sets of the 3931829/30 rear pipes [none for sale]. Both are double-walled. I also have several forward pipes [none for sale], all are double walled. I'm not going to dig them all out but I do have previous photos I have taken of a few including a GM #3931829 and GM #334932 (big block forward). All are clearly double walled.

DSCN3186.jpgDSCN3185.jpgDSCN2918.jpgDSCN2919.jpgDSCN3190.jpgDSCN3188.jpgDSCN3187.jpg

[Dave S.]

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

Mick,
That undercarriage photo looks like it is from my former 71 LT-1 #16798. The Rockwell label on the tire tub looks extremely familiar.
If so that car had an original muffler on the drivers side and a replacement Walker muffler on the passenger side when I sold it several years ago.
Otherwise the chassis was an excellent original example.

[Mick D.]

Mick,
That undercarriage photo looks like it is from my former 71 LT-1 #16798. The Rockwell label on the tire tub looks extremely familiar.
If so that car had an original muffler on the drivers side and a replacement Walker muffler on the passenger side when I sold it several years ago.
Otherwise the chassis was an excellent original example.

[Mick D.]

Gary-------

I need to clear up some things here.

The last 2-1/2" small block exhaust manifold was for 1965. After that, all small blocks with 2-1/2" exhaust required forward pipes with a transition section from the manifold's 2" outlet to 2-1/2"

1968 small blocks with MT used the exact same right side forward pipe as 1966-67, GM #3877210. The left side pipe was different and of GM #3913895. Both of these pipes used a welded transition section. Both of these pipes were exactly the same in PRODUCTION and SERVICE. Both were of double wall construction. As a matter of fact, in this case, if PRODUCTION was double walled, then SERVICE had to be double wall because they were the exact same part PRODUCTION or SERVICE.

As far as the rear pipe and mufflers go, it was like this. In PRODUCTION, the 1968 rear pipes and mufflers, both standard and N-11, were an assembly with the pipes welded directly to the mufflers. These were never available in SERVICE (although such assemblies were available in SERVICE for 1963-67 N-11). In SERVICE, the pipes and mufflers were only available separately. The rear pipes were 7" shorter than the PRODUCTION pipes to allow for connection to SERVICE mufflers which had welded-on curved extensions on the forward side. However, except for the 7" shorter length, the pipes were identical to PRODUCTION. If SERVICE mufflers were installed to original pipes, the pipes had to be commensurately shortened. Both PRODUCTION and SERVICE rear pipes were double-walled. Also, the 1968 427 rear pipes and mufflers. both PRODUCTION and SERVICE, were the same as small block.

The 1968 SERVICE mufflers for standard exhaust, GM #3943385 and 3943386 were the same as PRODUCTION except for the aforementioned forward extension and the fact that they included both the C2 and C3 hanger brackets. These same SERVICE mufflers replaced the C2 2-1/2" mufflers, GM #3820639/40 (1963-64) and 383846535/6 (1964-67). They also replaced the 1968 N-11 SERVICE mufflers, GM #3931803/4. The aforementioned C2 mufflers included only the C2 style hanger bracket and NOT the dual brackets of the GM #3943385/6. The 1968 N-11 SERVICE mufflers I mentioned were the ONLY C3 2-1/2" mufflers that were ever supplied with only C3 hanger brackets. No other 2-1/2" C3 SERVICE mufflers were ever equipped with only C3 hanger brackets.

The 1970-72 LT-1 PRODUCTION exhaust system was EXACTLY the same as the 1968 small block with MT PRODUCTION exhaust systems. The 1970-72 LT-1 SERVICE exhaust system was EXACTLY the same as the 1968 small block SERVICE exhaust system.

In late 1972-early 1973 the 1968 small block and 1970-72 LT-1 SERVICE forward exhaust pipes were replaced by GM #334925 and 334926, These are the same forward pipes used in PRODUCTION and SERVICE for 1973-74 Corvettes with L-82. These are the pipes with the "swaged" transition section from 2" to 2-1/2" and are double-walled. By the way, 1973-74 big block forward pipes were also replaced for PRODUCTION and 66-72 SERVICE by GM #334932 and 334933 about the same time. These pipes are also double walled.

Here's the story on part numbers:

1968 small block (non-N-11) with MT and all 1970-72 LT-1:

forward pipes:

LH GM #3931985 >11/72> 334925 > discontinued w/o supersession 1/93

RH GM #3877210 > 6/73> 334926 > discontinued w/o supersession 11/92

rear pipes:

LH GM #3931829 > discontinued w/o supersession 11/91

RH GM #3931830 > discontinued w/o supersession 8/90

mufflers:

LH GM #3943385 > discontinued w/o supersession 1/93

RH GM #3943386 > discontinued w/o supersession 1/93



I know nothing of any GM supplied SERVICE exhaust pipes, PRODUCTION or SERVICE that were anything but double-walled. I have 2 sets of the 3931829/30 rear pipes [none for sale]. Both are double-walled. I also have several forward pipes [none for sale], all are double walled. I'm not going to dig them all out but I do have previous photos I have taken of a few including a GM #3931829 and GM #334932 (big block forward). All are clearly double walled.

[ATTACH=CONFIG]116755[/ATTACH][ATTACH=CONFIG]116756[/ATTACH][ATTACH=CONFIG]116757[/ATTACH][ATTACH=CONFIG]116758[/ATTACH][ATTACH=CONFIG]116760[/ATTACH][ATTACH=CONFIG]116761[/ATTACH][ATTACH=CONFIG]116762[/ATTACH]

[Dave S.]

[Gary B.]

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

FWIW.. Walker numbers for 70-72 LT-1

44519 RH Front pipe
44518 LH Front pipe

45544 RH Center Pipe
45542 LH Center Pipe

21589 RH Muffler
21588 LH Muffler

These are out of a 1976 Walker Master Catalog.

Gary Bosselman

[Mick D.]

[Mick D.]

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

Great info again Gary - thank you very much for all of the detail.

FWIW.. Walker numbers for 70-72 LT-1

44519 RH Front pipe
44518 LH Front pipe

45544 RH Center Pipe
45542 LH Center Pipe

21589 RH Muffler
21588 LH Muffler

These are out of a 1976 Walker Master Catalog.

Gary Bosselman

[Joe L.]

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

FWIW.. Walker numbers for 70-72 LT-1

44519 RH Front pipe
44518 LH Front pipe

45544 RH Center Pipe
45542 LH Center Pipe

21589 RH Muffler
21588 LH Muffler

These are out of a 1976 Walker Master Catalog.

Gary Bosselman

Gary------

Do you happen to have any of these Walker mufflers and pipes? If so, I'd love to see photos of them.

[Dave S.]

[Gary B.]

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.

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