Stock exhaust questions Y and muffler fitment

[john r. lebetski]

Removing PO mufflers which are too short body length with added pipes up front. Finally got them off and though 2.25 in and 2.25 out they neck down to
like 1.5 " as soon as the pipe passes the end plates! Talk about restriction on a 455!
I have factory head pipes. Factory Y. NOS GM long pipes and NOS GM tail pipe from when Gateway still had them. For new mufflers I have
1) 2 very clean GM take offs for examples
2) 2 NAPA/Walker replacements (junk as single wall body and possible floor char)
3) 2 Canadian built dual wall exact GM body shaped copies I sourced from my muffler supplier.
Plan is to install the new Canadian prototypes and if they work out make them available as a solid replacement for those who retain a stock system.
My questions are about sexes on the OEM setup. The 2.25" head pipes fit into the mufflers which are set up to accept 2.25"pipe. It appears the
muffler outlets and the Y inlets are the same size so that a 4 inch ?? short 2.25" pipe section is needed to join them? Also if someone has a stock
Y, are both 2.25 legs equal length? It appears that someone cut the drivers leg about 2" shorter perhaps an easy way out when the joiner pipe is stuck
in there. I found it easy to use a fine blade sawzall into the end of the inner pipe and cut through to the outer and stop. Then you can fold and
chisel the inner pipe and it comes right out. I can simply make this 2.25" joiner longer to compensate for the shorter leg, unless the drivers side
muffler is supposed to sit rearward of the passenger side by 2" but I don't think so. Thanks.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[dennis sexton]

John

Here's a photo of my original exhaust Y section.
As you see, the 2 1/2 is necked down to fit the muffler and the other leg is 2 1/4.

Not sure when I can get to the storage location to measure the legs.

Hope this helps.
Dennis

http://www.gmcmhphotos.com/photos/1973-gmc-23ft-torsion-bar-assembly-details/p41893-gmc-torsion-bar-and-lca-008.html

> Removing PO mufflers which are too short body length with added pipes up front. Finally got them off and though 2.25 in and 2.25 out they neck
> down to like 1.5 " as soon as the pipe passes the end plates! Talk about restriction on a 455!
> I have factory head pipes. Factory Y. NOS GM long pipes and NOS GM tail pipe from when Gateway still had them. For new mufflers I have
> 1) 2 very clean GM take offs for examples
> 2) 2 NAPA/Walker replacements (junk as single wall body and possible floor char)
> 3) 2 Canadian built dual wall exact GM body shaped copies I sourced from my muffler supplier.
> Plan is to install the new Canadian prototypes and if they work out make them available as a solid replacement for those who retain a stock
> system.
> My questions are about sexes on the OEM setup. The 2.25" head pipes fit into the mufflers which are set up to accept 2.25"pipe. It appears the
> muffler outlets and the Y inlets are the same size so that a 4 inch ?? short 2.25" pipe section is needed to join them? Also if someone has a stock
> Y, are both 2.25 legs equal length? It appears that someone cut the drivers leg about 2" shorter perhaps an easy way out when the joiner pipe is
> stuck in there. I found it easy to use a fine blade sawzall into the end of the inner pipe and cut through to the outer and stop. Then you can fold
> and chisel the inner pipe and it comes right out. I can simply make this 2.25" joiner longer to compensate for the shorter leg, unless the drivers
> side muffler is supposed to sit rearward of the passenger side by 2" but I don't think so. Thanks.

--
Dennis S
73 Painted Desert 230
Memphis TN Metro

 

[john r. lebetski]

Thanks. I have a plan.
Hoping for big performance increase after examining the old wrong mufflers. Will report when finished.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Matt Colie]

You are lucky.

As I (fortunately) decided to pull the engine out the front and could not get the manifold fasteners loose (any), the whole affair came out with the
exhaust up to the straight pipe in tow. This was when I discovered that both of the (badly) welded in mufflers were about to breach at the top.
While the Y-pipe seems to be sound, salvaging it will be a day-long job of sawing and grinding. I know it will take that long because one of the head
pipes still has a GM part number on it, so I took the time to save that. The rest will await more inspection and free time.

I am putting back in a stainless system from Applied with everything (including the mechanic) coated in anti-sieze. I really want it to come apart
easily the next time, but that will probably not be me doing it.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[john r. lebetski]

Matt I have 2 beautiful take off mufflers and head pipes and a tail pipe. (Spout in GM speak). I sourced the mufflers to be an exact length and oval
profile shape. If I can find a good Y I can have these all reproduced in alluminized USA pipe. The 2 long pipes are easy!!! I know there are
aftermarket solutions but I hope to be able to provide pieces parts a la carte or as a stock replacement system. My cheapo PO mufflers had heat
discoloration probably not long from burnout. I had noticed less than expected power on the secondaries compared to all the other Qjet vehicles I have
driven over the years and bet it was these old restrictive mufflers. My springbolts were cake to remove. But the head pipe to manifold angle was wrong
and kept blowing the Fed Mogul packings. That is what started the whole adventure.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[john r. lebetski]

Just finished install and they sound great nice and quiet. The dual walls really cut the tinny resonance up front when standing next to coach. I will
contact my supplier for pricing and build time and maybe can bring sets to Amana.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Matt Colie]

> Matt I have 2 beautiful take off mufflers and head pipes and a tail pipe. (Spout in GM speak). I sourced the mufflers to be an exact length and
> oval profile shape. If I can find a good Y I can have these all reproduced in alluminized USA pipe. The 2 long pipes are easy!!! I know there are
> aftermarket solutions but I hope to be able to provide pieces parts a la carte or as a stock replacement system. My cheapo PO mufflers had heat
> discoloration probably not long from burnout. I had noticed less than expected power on the secondaries compared to all the other Qjet vehicles I
> have driven over the years and bet it was these old restrictive mufflers. My springbolts were cake to remove. But the head pipe to manifold angle
> was wrong and kept blowing the Fed Mogul packings. That is what started the whole adventure.

John,

Let me look at the Y pipe that is on my scrap pile. If you are interested, I could drag it to Amana.

Matt

--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[john r. lebetski]

Excellent. What I found is the drivers leg is the continuation of the main pipe and accepts 2.25 pipe internally. The passenger leg is welded on as
a "tributary" and is actual 2.25 pipe (smaller than drivers side) the muffler slips over. So drivers side required about a 6" section of straight 2.25
as a coupler. This finally squared up the head pipe to the casting and places the drivers muffler slightly fore of the passenger's side. In looking at
the chassis picture in the GMC History article I found this to be correct! Things on underbodies are not always symmetrical though we in our minds
think they should be. I found in the Regals the rear foot well stampings do not line up fore and aft which explains the asymmetry in their factory Y
pipe. Also certain GTOs used a shorter and longer muffler combination as built.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[les burt]

Looking at the photo Dennis provided, it appears as though the driver’s side of the exhaust Y pipe is 2.5”, necked down to 2.25” so it will slip into the muffler. The old rusty Y From my coach is made the same way, but I have no way of telling if it is an original TZE part or a jobber replacement since it is beyond rusty.

Les Burt
Montreal
'75 Eleganza 26'

>
> Excellent. What I found is the drivers leg is the continuation of the main pipe and accepts 2.25 pipe internally. The passenger leg is welded on as
> a "tributary" and is actual 2.25 pipe (smaller than drivers side) the muffler slips over. So drivers side required about a 6" section of straight 2.25
> as a coupler. This finally squared up the head pipe to the casting and places the drivers muffler slightly fore of the passenger's side. In looking at
> the chassis picture in the GMC History article I found this to be correct! Things on underbodies are not always symmetrical though we in our minds
> think they should be. I found in the Regals the rear foot well stampings do not line up fore and aft which explains the asymmetry in their factory Y
> pipe. Also certain GTOs used a shorter and longer muffler combination as built.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
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