72 Small Block Exhaust System

[Dave S.]

Re: 72 Small Block Exhaust System

Joe,
Help me to clear up some confusion on my part.

I have some original 2" center exhaust pieces taken from a 71 as well as NOS 2" pieces for a 71 and all do not show a flattened center pipe. All the pipes have the wrinkled bends that one would expect to see on an original GM system. I'm not familiar with 68 or 69 pipes but all 70-72 2" pipes I've seen have not been flattened. The GM service part numbers for 2" pipes are the same for 69 thru 72 but 68 numbers are different.

Also all the original pieces I have are double wallled. I know you have indicated previously that original pipes were not built that way.

The Allens 2 1/2" LT-1 system shown in the photos is very nice. The swegded header pipe is especially nice. Finally we have something that looks right on our LT-1's and LS-5's. .

Any guidance is appreciated

[Gerard Q.]

Re: 72 Small Block Exhaust System

Edward - I spoke with Eric today. Super nice guy, and seems to be a real enthusiast as well as a great businessman.
I offered him my 2" pipes, which I'm told are original or NOS, to make repos. His two concerns seemed to be: 1) Is there enough of a market to justify the cost of making 2" dies; and 2) my rear pipes were apparently cut to fit replacement mufflers extensions, so they don't extend all the way back to mufflers like originals would.
He told me he'd get back to me. I told him I'd love to help all those who'll want correct 2" pipes, which would include me since my carbon steel pipes won't last forever. I'm hoping Gardner will decide to go forward for all us 2" guys ... exhaust pipes width, that is.

I'd be interested....think of it this way there are a lot more sb owners out there than bb/LT1 owners. I think there would be a lot of interest in a "correct" 2" system.

[Thomas G.]

Re: 72 Small Block Exhaust System

Let me state for the record that Gardner Exhaust Systems is very interested in reproducing the 2" exhaust systems. What we need is original pipes from someone who can give them or lend them to us for a considerable amount of time to copy. We would have to create a die to make the wrinkle bends which is no big thing but we would need time to do it.

Pat is a very nice guy and a true hobbiest who seemed generally interested in helping us get the original pipes but since his pipes are the ones he is using in the car it may be a difficult system to engineer quickly and we wouldn't want Pat to miss any crusie ins.

I would also like to state that in a previous thread somone mentioned that Allen's is the company that is supplying the correct 2 1/2" necked down head pipes and wrinkled system, I am sure that this is just a typo but after we went through all the work making this system we certainly would like the credit.

So to recap. If someone out there has original pipes for 1970 - 1973 small block non high performance cars and is willing to send them to us we will purchase them outright or replace new for old as long as they give us some time to do so.

Best Regards,

Eric Gardner

[Jack H.]

Re: 72 Small Block Exhaust System

"But I would say that is a good looking exhaust, now if we could just get the W in the mufflers"

Most believe (and are willing to put their lawyers to work...) that parts made with any/all of the original manufacturer's 'marks' require licensing to take to market. Licensing fees vary, but what's typical in the auto parts business is something in the neighborhood of $50K.

For a little guy who's not sure of what his total production volume of a given part is going to be, that can be a 'deal killer' for a product's start-up cost profile!

[Joe L.]

Re: 72 Small Block Exhaust System

Joe,
Help me to clear up some confusion on my part.

I have some original 2" center exhaust pieces taken from a 71 as well as NOS 2" pieces for a 71 and all do not show a flattened center pipe. All the pipes have the wrinkled bends that one would expect to see on an original GM system. I'm not familiar with 68 or 69 pipes but all 70-72 2" pipes I've seen have not been flattened. The GM service part numbers for 2" pipes are the same for 69 thru 72 but 68 numbers are different.

Also all the original pieces I have are double wallled. I know you have indicated previously that original pipes were not built that way.

The Allens 2 1/2" LT-1 system shown in the photos is very nice. The swegded header pipe is especially nice. Finally we have something that looks right on our LT-1's and LS-5's. .

Any guidance is appreciated

Dave-----


First, the reason that the 1968 exhaust system part numbers are different is because ALL 1968 Corvettes used 2-1/2" exhaust; NONE were 2", including base engine.

As far as the "flattening" of the rear 2" pipes, I am 100% sure that 1969 had that configuration. I remember it very well on my original pipes. In fact, I well recall being disappointed when the new stainless steel system I installed in the 80's didn't have the "flattened" configuration. I don't know if I saved the original pipes, or not. If I did, I don't know where I put them. However, as I say, I am 100% certain that they were "flattened". The "flattening" was not as pronounced as it was on the 2-1/2", but the cross section of the pipes was DEFINITELY not round for the center portion of the pipes.

While the forward 2" pipes were the same, PRODUCTION or SERVICE, for all 1969-72 there was a change in the part numbers for the PRODUCTION rear pipes. For manual transmission cars, 1969 were 3952719 and 3952720 while 1970-72 were 3974655 and 3974656. However, keep in mind that these are pipe/muffler ASSEMBLIES and I don't think there was any difference in the pipe section of these assemblies between 1969 and 70-72. I think the difference was that the mufflers for 70-72 had the "pin" welded on the bottom of the outlet pipe for alignment of the tip.

The SERVICE rear pipes for 1969-72 were always the same, from "day 1 1969" until the pipes were discontinued in 1988 and 1989. I don't have any of these pipes but I would not expect them to be any different from PRODUCTION except for the shorter length to accommodate the muffler extension pipe.

I do not understand, at all, why the ones you describe show no evidence of "flattening". It may be that I had the only 1969-72 Corvette originally built with 2" pipes that were "flattened", but I am 100% certain they were.

As far as the "double wall" goes, how do you know that the pipes you have are "double walled"? I have never seen any evidence of a "double wall" at either end of these pipes. So, if they are "double walled", the secondary wall must not extend to the ends of the pipes. Have you ever cut in half a pipe toward the center and observed a double wall?

[Terry M.]

Re: 72 Small Block Exhaust System

I have seen pipes for sale at the swap meets (in the old days when there were real swap meets) that had dragged on the ground and had a hole worn into them. The two thicknesses of pipe were easy to see. Also lift the pipes -- the weight will tell you right off they are double wall.

It might be that only the 2.5 inch systems were double wall. I can't say that I paid much attention to the smaller systems, so my experience is with the larger pipes.

I have lifted some NOS Mark IV header pipes that I am sure were double wall just by their weight.

[Bill C.]

Re: 72 Small Block Exhaust System

I have always wondered if the "double walling" of the NOS CS pipe was to aid in bending and flattening the pipe.

Maybe Walker figured out that the sigle wall CS pipe used durring assembly had issues going through the bending process.

I used to work at a Meineke when I was in college (1982-87) and I saw some really bad things happen to these pipes. One incident the inner pipe seperated from the outer pipe and nearly collapsed. They do take a whole lot longer to rust though - a saving grace!


I guess this secret will stay a secret

As stated above, the weight of double wall pipe is very evident.
Only pipes I can comment on are NOS 2.5" for BB and LT1 cars.

[Al S.]

Re: 72 Small Block Exhaust System

I'd be interested....think of it this way there are a lot more sb owners out there than bb/LT1 owners. I think there would be a lot of interest in a "correct" 2" system.

I agree with Gerry, I'd be interested.
Base motor small blocks far out number the LS5's and LT1's.

[Dave S.]

Re: 72 Small Block Exhaust System

Dave-----


First, the reason that the 1968 exhaust system part numbers are different is because ALL 1968 Corvettes used 2-1/2" exhaust; NONE were 2", including base engine.

As far as the "flattening" of the rear 2" pipes, I am 100% sure that 1969 had that configuration. I remember it very well on my original pipes. In fact, I well recall being disappointed when the new stainless steel system I installed in the 80's didn't have the "flattened" configuration. I don't know if I saved the original pipes, or not. If I did, I don't know where I put them. However, as I say, I am 100% certain that they were "flattened". The "flattening" was not as pronounced as it was on the 2-1/2", but the cross section of the pipes was DEFINITELY not round for the center portion of the pipes.

While the forward 2" pipes were the same, PRODUCTION or SERVICE, for all 1969-72 there was a change in the part numbers for the PRODUCTION rear pipes. For manual transmission cars, 1969 were 3952719 and 3952720 while 1970-72 were 3974655 and 3974656. However, keep in mind that these are pipe/muffler ASSEMBLIES and I don't think there was any difference in the pipe section of these assemblies between 1969 and 70-72. I think the difference was that the mufflers for 70-72 had the "pin" welded on the bottom of the outlet pipe for alignment of the tip.

The SERVICE rear pipes for 1969-72 were always the same, from "day 1 1969" until the pipes were discontinued in 1988 and 1989. I don't have any of these pipes but I would not expect them to be any different from PRODUCTION except for the shorter length to accommodate the muffler extension pipe.

I do not understand, at all, why the ones you describe show no evidence of "flattening". It may be that I had the only 1969-72 Corvette originally built with 2" pipes that were "flattened", but I am 100% certain they were.

As far as the "double wall" goes, how do you know that the pipes you have are "double walled"? I have never seen any evidence of a "double wall" at either end of these pipes. So, if they are "double walled", the secondary wall must not extend to the ends of the pipes. Have you ever cut in half a pipe toward the center and observed a double wall?

Joe,
I'm no expert but I'm going by the used and NOS examples I have. I have an original used 3974655 pipe which was shortened to install a new muffler. It is not flattened and is double wllled.

The NOS pieces I have are 3960603 and 3960606. Both have GM parts labels on them. They are shortened to accomidate the service muffler as you describe. They are definately not flattened and are definately double walled. I cut a small piece from each and you can clearly see it is a double walled pipe. I saved a 1" long slice of the NOS pipe which I'd be glad to send you so you can see it. I realize that they are service pieces and could be configured differently than the original pipe/muffler assemblies but I can say for sure those NOS pipes are constructed/configured as mentioned.
There is slight flattening at the short straight run near the muffler end but it is very slight. The long run of the pipes in both cases are round.
I am familiar with the 70-72 - 2 1/2" systems in both original and service configurations as I have a mix of both on my LT-1 cars but I have never taken a cut to see if either or both are double walled.
I'm sure your 69 2" pipes were flattened but I'm just wondering why the service pipes I have are not and one original pipe section is not either.
I also want to be sure once Gardner or any othe exhaust vendor reproduces these 2" systems that they are correct.
I would be nice to find an original base engine 69-72 car to assist us with this.

[Joe L.]

Re: 72 Small Block Exhaust System

Joe,
I'm no expert but I'm going by the used and NOS examples I have. I have an original used 3974655 pipe which was shortened to install a new muffler. It is not flattened and is double wllled.

The NOS pieces I have are 3960603 and 3960606. Both have GM parts labels on them. They are shortened to accomidate the service muffler as you describe. They are definately not flattened and are definately double walled. I cut a small piece from each and you can clearly see it is a double walled pipe. I saved a 1" long slice of the NOS pipe which I'd be glad to send you so you can see it. I realize that they are service pieces and could be configured differently than the original pipe/muffler assemblies but I can say for sure those NOS pipes are constructed/configured as mentioned.
There is slight flattening at the short straight run near the muffler end but it is very slight. The long run of the pipes in both cases are round.
I am familiar with the 70-72 - 2 1/2" systems in both original and service configurations as I have a mix of both on my LT-1 cars but I have never taken a cut to see if either or both are double walled.
I'm sure your 69 2" pipes were flattened but I'm just wondering why the service pipes I have are not and one original pipe section is not either.
I also want to be sure once Gardner or any othe exhaust vendor reproduces these 2" systems that they are correct.
I would be nice to find an original base engine 69-72 car to assist us with this.

Dave-----


Can you post photos of the pipes you have and also a photo of the 1" cut-out piece showing the double wall?

[Dave S.]

Re: 72 Small Block Exhaust System

Dave-----


Can you post photos of the pipes you have and also a photo of the 1" cut-out piece showing the double wall?

Joe,
These are photos of the double wlll and a part number tag. I will post a photo of the used original pipe.

[Dave S.]

Re: 72 Small Block Exhaust System

Joe,
These are photos of the double wlll and a part number tag. I will post a photo of the used original pipe.

More Photos

[Louie M.]

Re: 72 Small Block Exhaust System

I happened to talk to Gardner today about availability of their flattened midpipes for my 67. They say that their new flattened exhaust pipes will indeed be flat, EXCEPT where there are bends. Acc. to them the factory had different tooling in order to make the pipes flat through bends, and Gardner can't afford to do that.

[Joe L.]

Re: 72 Small Block Exhaust System

I happened to talk to Gardner today about availability of their flattened midpipes for my 67. They say that their new flattened exhaust pipes will indeed be flat, EXCEPT where there are bends. Acc. to them the factory had different tooling in order to make the pipes flat through bends, and Gardner can't afford to do that.

Louie-----


That does not surprise me in the least. I've said for a long time that I believe the original pipes were die-formed. That's also why the original pipes fit so well---the dies were made for an exactly formed pipe and the exact same pipe was manufactured each time. Thus, there was negligible variation between pieces.

I've also said before that there's no way to exactly reproduce the original pipe configuration unless the original or exact duplicate dies were used. Apparently, the original dies are no longer available. I would expect that it would be economically infeasible to re-create them. So, reproductions are mandrel bent and "nuanced" to create certain original features that can't be re-created with mandrel bending. However, it's not possible to EXACTLY re-create all aspects of original configuration this way.