Is there a stock dual exhaust system for a 78 GP with 301

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lonewolf

Not-quite-so-new-guy
Looking for a supplier for a dual exhaust system for a 78 GP with a 301.
First choice would be a true dual system.
Second choice would be a single system up front with 2 outlet pipes, in other words appears to be duals.
As close to original sound as possible.
 

fleming442

Captain Tenneal
Dec 26, 2013
13,046
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I made one out of 2.5" mandrel bent, Chinese parts and a 4th gen F-body muffler. Shouldn't any G-body, cat back system work? I know the one muffler guy I went to really didn't want to do it because of the complexity of the over axle bends.
 
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565bbchevy

Geezer
Aug 8, 2011
9,591
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Michigan
When I replaced the exhaust on my 86' Regal with a 307 I was looking at the Monte replacement cat back system but the convertor flange was different from my Olds flange and won't bolt up so I am guessing there will be an issue with the 301 also
 
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spidereyes455

G-Body Guru
Mar 6, 2013
776
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Northeastern PA
The Hurst Olds and 442 vin 9 exhaust should work with your original converter ,that is if you can find it anymore. It seems to have been discontinued from Walker in the past year or so. Might still be able to piece one together if you search around enough.
It used to be a really popular upgrade for lots of g bodys before aftermarket kits were widely available .
 
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lonewolf

Not-quite-so-new-guy
Re Summit system " a rich throaty tone that can not be ignored "
Sorry looking for as close to original as possible in other words ...silence.

I live in Ontario, Canada but can source from American suppliers quite easily ( if this virus scare is uver come and travel is permitted)
 

oldsmobile joe

Royal Smart Person
Nov 12, 2015
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When I replaced the exhaust on my 86' Regal with a 307 I was looking at the Monte replacement cat back system but the convertor flange was different from my Olds flange and won't bolt up so I am guessing there will be an issue with the 301 also
your converter is a honey comb style. his is the old pellet style (its large, like a snapping turtle). there was no factory dual exhaust for his year gp or even a dual outlet muffler. some other early g body cars came with dual outlet mufflers, but have been discontinued. there is the summit kit, jegs has one as well as pypes and holley have options to choose from.
a good exhaust shop should be able to weld one up like FLEMMING442 mentioned in his post. the camaro dual outlet muffler does cross reference with the early g body muffler.
 
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383_GrandPrix

G-Body Guru
Sep 9, 2016
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You could buy the Pypes cat-back w/o mufflers and buy a quieter set of mufflers of your choice. As far as using a F body muffler, I tried to do that on my GP using exhaust parts that were laying around and it didn't work so well as the muffler was larger then the G body muffler. If you were to have an exhaust shop fabricate an exhaust I'm sure they could make the F body muffler work but I don't know what price point you'll be at.
 
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pontiac guy

G-Body Guru
Oct 28, 2016
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Royse City, TX
I am doing duals on my 78 GP SJ with a 301 right now. It had the original exhaust all the way back to the factory dual outlet muffler. First, yes you can use a third or 4 gen muffler but it isn't easy or exceptionally clean. The muffler inlet (drivers side for this car) and driver's tailpipe are flipped on the f body muffler vs the factory g body dual outlet because the f body mounts in a different orientation. A muffler shop could overcome this but if you are trying to do it with auto parts store stuff it's not so easy. The f body tail pipes are also larger and won't fit so you have to make them or modify/adapt the smaller gbody stuff. This is not a bad route to go. I will warn you that the f body stuff is stupid quiet on a g body. So quiet people commented on it to me. That sums up the dual outlet f body exhaust. Which wasn't really your question.
It's been stated correctly there is no factory dual exhaust for this car. But you obviously want duals, and the factory y pipe and exhaust are a whopping 2 inches AND has more kinks than R Kelly. This is my answer to that problem.

I am using a dual system from a SBC car that is hedder back. So that gets you over the axles and tailpipes. From the motor you need to be creative. First do you want to retain the heat riser on the driver's side? Are you OK with just leaving it in and stuck open? If not you need a drivers manifold from a 68-72 A body (there may be others but that's what I had). It is rear exit. Most Pontiacs are center exit. Maybe you can make that work I didn't want to try it, especially with my clutch linkage. Next the 301 uses the triangular 3 bolt flange. No one offers those (that I can find). So order 2 walker 41475 exhaust adapters from your favorite auto parts supplier. They come with 2 bolt flanges. Cut the pipe in half in the middle and slide them off. Save them for another job. Move your original flanges over. Weld the exhaust adapter back together. Now you have the correct flanges and a 2 1/4 exhaust stub. Fabricate from there using the appropriate parts from your favorite source to connect to the SBC system you are using. I recommend starting from the rear and working forward.

An alternative to cutting the pipe in half to change flanges is to cut the 2 bolt flange off and get a repair 3 piece flange. Autone has them. They look like a box of Lincoln logs but it will work. They aren't cheap either.

Good luck. If you come up with a better way fill me in. I hate doing exhaust. Love shirt cuts and cheat codes
 
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