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 New exhaust system

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91rdmastr



Posts : 62
Join date : 2020-02-13

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PostSubject: New exhaust system    New exhaust system  Icon_minitimeFri Feb 21, 2020 7:10 pm

Hey guys...I need to put a new exhaust system on my Roadmaster. I have headers on my truck and am tired of them working loose constantly so I don't want them on my longroof. My plan is to upgrade the manifolds to a pair of 350s...but what should I use? I've read there are a couple different sets that will work but one is a "higher flowing" manifold. I'm staying with the single exhaust and will get a 2 1/2" y -pipe, high flow cat and a single in to a dual out and exit my exhaust in front of each rear wheel well. Thanks for the input!
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91rdmastr



Posts : 62
Join date : 2020-02-13

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeFri Feb 21, 2020 7:13 pm

I also plan on running 3" from the y-pipe to the muffler and 2 1/2" out to Gibson tips.
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94Woody

94Woody

Posts : 1960
Join date : 2008-12-02
Age : 45
Location : Belleview,FL

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeFri Feb 21, 2020 7:56 pm

Honestly I wouldn't bother with the manifolds at all. They are not a choke point on the old TBI cars anyways. Swirl port heads only "flow" so much and it isn't much at all.
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Fred Kiehl

Fred Kiehl

Posts : 5799
Join date : 2009-11-13
Age : 72
Location : Largo, FL 33774

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeSat Feb 22, 2020 7:31 am

You have some surprises coming. You will have to use a muffler that brings the exhaust back out of the front, so you have room to turn the pipe for an "in front of the wheel" outlet. You also must get the left pipe to cross over without interfering with the drive shaft. That style muffler is available.

I use these header bolts https://www.jegs.com/i/Proform/778/66753/10002/-1 on my BBC in my 91 OCC, and my 350 in my 92 OCC. They have not loosened in about a year of driving on either car. They are 1 inch long, and depending on the thickness of the header flange, you may need the 3/4 inch length. https://www.jegs.com/i/Proform/778/66751/10002/-1

I have shorty headers on my 92, and duals. It seems to have a bit more get up, and go than the stock exhaust. I dumped the exhaust at the axle on both cars. I did have to make a hump in the trans crossmember. I also found that the cars have the holes to mount a muffler hanger on the driver's side of the crossmember in front of the axle for duals. You can use one from another 91-93. I put the O2 sensor bung on the driver's side header, and my computer seems to like the setup. If you have the correctly tuned headers, it can help with the evacuation of the exhaust gasses, and make the heads seem flow a little bit better.
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91rdmastr



Posts : 62
Join date : 2020-02-13

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeSat Feb 22, 2020 1:08 pm

I don't understand what you mean by "bring the exhaust back out of the front"
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Fred Kiehl

Fred Kiehl

Posts : 5799
Join date : 2009-11-13
Age : 72
Location : Largo, FL 33774

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeSat Feb 22, 2020 4:14 pm

There is not enough room to turn the exhaust behind the muffler and bring it out in front of the wheel opening. The standard muffler exit is about 6 inches from the axle.
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rcktpwrd

rcktpwrd

Posts : 313
Join date : 2019-03-06
Age : 46
Location : Raleigh, NC

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeSat Feb 22, 2020 4:28 pm

91rdmastr wrote:
I don't understand what you mean by "bring the exhaust back out of the front"

you can get mufflers that have the inlet and outlet on the same side...

https://www.dynomax.com/super-turbo-offset-offset-same-side.html
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Fred Kiehl

Fred Kiehl

Posts : 5799
Join date : 2009-11-13
Age : 72
Location : Largo, FL 33774

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeSat Feb 22, 2020 4:48 pm

That is the one. You will probably need oval exhaust pipes for ground clearance under the body and frame.
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91rdmastr



Posts : 62
Join date : 2020-02-13

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeMon Feb 24, 2020 2:33 pm

LOL...I've seen a lot of different mufflers but don't understand how that's supposed to work.
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Fred Kiehl

Fred Kiehl

Posts : 5799
Join date : 2009-11-13
Age : 72
Location : Largo, FL 33774

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeMon Feb 24, 2020 2:46 pm

You will have to figure it out, but it is the only way to get the exhaust to exit in front of the wheels. You need to have duals to do it.
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94Woody

94Woody

Posts : 1960
Join date : 2008-12-02
Age : 45
Location : Belleview,FL

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeMon Feb 24, 2020 7:58 pm

91rdmastr wrote:
LOL...I've seen a lot of different mufflers but don't understand how that's supposed to work.

It works the same as every other muffler. Exhaust enters through one side and exits the other. Inlet and outlet are on the same side so the pipes can be properly routed to the front of the rear wheels.

Personally, I wouldn't bother with that set up. Either dump it in front of the axle or run some tail pipes.
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91rdmastr



Posts : 62
Join date : 2020-02-13

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeTue Feb 25, 2020 12:11 am

Its been lowered a littleNew exhaust system  20200216
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91rdmastr



Posts : 62
Join date : 2020-02-13

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PostSubject: Re: New exhaust system    New exhaust system  Icon_minitimeTue Feb 25, 2020 12:12 am

There are more pics in the pic section
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