1970-1972 NOS LT-1 Exhaust system

[Ralph S.]

How desirable is an over the counter system purchased in 1985 compared to a Gardner system.

[Bill C.]

Re: 1970-1972 NOS LT-1 Exhaust system

hmmmmmm

that would depend on what kinda restoration you are doing or how close to original you want.
the doubled walled pipes sound completely different than single wall.
the 385/386 mufflers have a sound that has not been reproduced - far as I am concerned... :-)
the bends in the back by the rear on the NOS pipes are not duplicated the same on Eric's system
plus the flattening and crinkle styles are not even close to the NOS pipes.

So ---
If I were in the market , I guess that set be worth around $2500 - $3000

btw.
the tips that Richard F. makes are damn near perfect and just like assembly line.
so the OTC tips you have, even though NOS, are less desirable -- IMHO
Richards tip sets run about $450 + shipping I think.
and judge really nicely.


To me ???? your system is VERY VERY desirable!!!


Bill

You need to give Ron Gadutti a call - he is always hunting down NOS system.
and maybe Stan Felenski and Paul Oslanski

[Mike E.]

Re: 1970-1972 NOS LT-1 Exhaust system

My memory may be faulty, but I don't remember the mufflers having dual brackets. The ones pictured do.

[Bill C.]

Re: 1970-1972 NOS LT-1 Exhaust system

they didn't

I had to separate the incorrect one from the 385/386 muffler set I got
and make it look nice..

If you are VERY lucky and find an OLD OLD nos set they may have just one bracket and will likely not have the GM part numbers embossed and will have the W in the right places.

[Russ S.]

Re: 1970-1972 NOS LT-1 Exhaust system

They are also incorrect because they clamp together in front of the muffler. Original did not. Gardners has that advantage over the OTC pieces.

[Bill C.]

Re: 1970-1972 NOS LT-1 Exhaust system

They are also incorrect because they clamp together in front of the muffler. Original did not. Gardners has that advantage over the OTC pieces.

but thats is an incredibly easy fix.
just butt weld the mufflers to the mid pipes and grind down and clean up.
will look damn near exactly like the assembly line system then.

that was what I did on my 72.
worked like a charm and judges well too.

Eric's system clamps to the back of the muffler.
to make his system assembly line correct you need to cut off the 2.5" pipe extension on the muffler back and them seam weld the pipe to the muffler.
the NOS 385/386 mufflers have the pipe extension welded correctly to the muffler assembly. It was also welded very close to the bend in the pipe, so that was not very much of a straight extension to the muffler.

this is why I think the OTC NOS pipe sets are a million times better.

Bill

[Joe L.]

Re: 1970-1972 NOS LT-1 Exhaust system

but thats is an incredibly easy fix.
just butt weld the mufflers to the mid pipes and grind down and clean up.
will look damn near exactly like the assembly line system then.

that was what I did on my 72.
worked like a charm and judges well too.

Eric's system clamps to the back of the muffler.
to make his system assembly line correct you need to cut off the 2.5" pipe extension on the muffler back and them seam weld the pipe to the muffler.
the NOS 385/386 mufflers have the pipe extension welded correctly to the muffler assembly. It was also welded very close to the bend in the pipe, so that was not very much of a straight extension to the muffler.

this is why I think the OTC NOS pipe sets are a million times better.

Bill

Bill------


I do not recommend trying to remove the SERVICE muffler extensions at the muffler. For one thing, the SERVICE rear exhaust pipe is not long enough to weld directly at the muffler. For another thing, even if one simply removes the slip joint section of the muffler extension and then attempts to weld the muffler extension to the rear pipe, one better have the muffler and pipe fitment PERFECT because no further adjustment will be possible.

My recommendation: install the SERVICE pipes and mufflers AS-IS and take whatever the judging "hit" is for the slip joint and clamp.

[Joe L.]

Re: 1970-1972 NOS LT-1 Exhaust system

They are also incorrect because they clamp together in front of the muffler. Original did not. Gardners has that advantage over the OTC pieces.

Russ-----


Which is their only advantage. And, if the assemblies don't fit properly when installed in the car it becomes a disadvantage because adjustment possibilities are VERY limited.

[Joe L.]

Re: 1970-1972 NOS LT-1 Exhaust system

they didn't

I had to separate the incorrect one from the 385/386 muffler set I got
and make it look nice..

If you are VERY lucky and find an OLD OLD nos set they may have just one bracket and will likely not have the GM part numbers embossed and will have the W in the right places.

Bill------


The GM #3943385 and 3943386 SERVICE mufflers were always dual bracket. The only way to get 2-1/2" mufflers with a single bracket is to obtain some of the predecessor part numbers. Those only have a single bracket but it's a 63-67 bracket. There never was a 68-72 2-1/2" muffler with a single C3 bracket. The 2" 68-72 mufflers did have a single C3 bracket, though.

[Ralph S.]

Re: 1970-1972 NOS LT-1 Exhaust system

What is the purpose of the 2 brackets on the mufflers

[Bill C.]

Re: 1970-1972 NOS LT-1 Exhaust system

to work on either a C2 or a C3

[Kenneth B.]

Re: 1970-1972 NOS LT-1 Exhaust system

you are correct. I bought a set in 1978 & they were the 2 bracket ones.

[Joe L.]

Re: 1970-1972 NOS LT-1 Exhaust system

What is the purpose of the 2 brackets on the mufflers

Ralph------

I think what likely happened was that GMSPO realized that the 63-67 2-1/2" mufflers were the same as the 1968 2-1/2" except for the brackets. So, they discontinued the 63-67 2-1/2" mufflers and replaced them with the dual bracket mufflers which ultimately became the 63-72 2-1/2" mufflers. This way, instead of having to stock 4 muffler part numbers, they only had to stock 2. The VAST, VAST majority of the folks that needed mufflers for any 63-72 Corvette didn't care about the extra bracket. If they did, they could remove the unused bracket with careful use of a die grinder.

The thing that I could never understand, though, is why they didn't do the same thing for the 2" mufflers. There was never a dual bracket version of these mufflers. So, solely because of the bracket difference, the 1963-67 2" mufflers were different than the 69-72 (there never was a 2" muffler used for the 1968 model year). In fact, maybe that's the answer to the question: the GMSPO guy that came up with the idea of consolidating part numbers in 1968 for the 2-1/2" mufflers was gone by the time that the 2" mufflers "came back" for the 1969 model year.

Now, there is a good possibility that there was once-upon-a-time a way to obtain C3 2-1/2" mufflers with a single bracket. For 1968, RPO N-11 (off-road exhaust) was offered for the last time. There were once available SERVICE mufflers for this application. These were supplied without rear exhaust pipe ( 63-67 N-11 mufflers were always supplied only with attached rear exhaust pipe). These mufflers were GM #3931803 and 3931804. They were discontinued in the fall of 1972 and replaced by the GM #3943385 and 3943386 standard exhaust 2-1/2" mufflers. (So, by the time that any 1968 owner with an original N-11 optioned car likely needed mufflers, they could no longer obtain true N-11 mufflers). I've never seen the 3931803 or 3931804. However, I would hazard a guess that they were single bracket, C3 style.

[Dave S.]

Re: 1970-1972 NOS LT-1 Exhaust system

you are correct. I bought a set in 1978 & they were the 2 bracket ones.

Are the embossed part numbers on the mufflers correct for 1970-1972.?
I believe the "wrinkle bends" on the header pipes are only seen in 1972.
The manifold ends of the header pipes are covered but they are likely a welded style which is different from the "swedged" detail used on assembly line header pipes.
Looks like the tips have part numbers on them. If so they are NTFP.

My opinion is that the $2500-$3000 estimate is ambitious.

[Joe L.]

Re: 1970-1972 NOS LT-1 Exhaust system

Are the embossed part numbers on the mufflers correct for 1970-1972.?

I don't think original mufflers had part numbers embossed on them. But, even if they did, they would have been different numbers than the ones embossed on SERVICE mufflers. That's because SERVICE mufflers did not include the rear pipe and had dual brackets.
I believe the "wrinkle bends" on the header pipes are only seen in 1972.

The original forward pipes for 1970-72 LT-1 were the same part number for PRODUCTION or SERVICE---GM #3913895, left, and GM #3877210, right. However, these were replaced on November, 1972 and June, 1973, respectively, by GM #334925, left, and GM #334926, right. I expect that the pipes shown in the original post are the later part numbers and one might expect them to be different in some ways than the originals. I'm surprised, though, that there would have been a difference in the "wrinkle bends". This feature is characteristic of pipes that are DIE-FORMED which most OEM pipes, PRODUCTION or SERVICE, are so-fabricated. Incidentally, die formed pipes are why OEM pipes fit so well as opposed to most aftermarket or reproduction pipes which are mandrel bent.
The manifold ends of the header pipes are covered but they are likely a welded style which is different from the "swedged" detail used on assembly line header pipes.

The later pipes I described above have the welded-on, reduced diameter section at the manifold flange end. These later pipes were also used in PRODUCTION for 1973-74 L-82.
Looks like the tips have part numbers on them. If so they are NTFP.

My opinion is that the $2500-$3000 estimate is ambitious.

Dave------


Please note my comments above