2.5" exhaust vs 2.25 or even 2"

[rumblefish360]

The real estate of the car will tell you where it goes. There’s not a lot of room under there.

 

[Hamerhead]

IMO , you are giving up both horsepower and torque by going to a 2 1/4" system . I have been told by several manufacturers of exhaust headers and systems that 425 engine horsepower is the cutoff point between 21 /2" and 3" systems . If you have a low production/numbers matching car then 2 1/4" is your deal . If you are planning headers I would go 2 1/2" . If you plan on h.p. upgrades I suggest 3". whats't he harm .

Car is a numbers matching 68 Dart GTS 383 auto. I likely will never do a full blown resto. But don't want to do anything that can't be easily undone

 

[Mattax]

IIRC there is a line drawing in the '68 Plymouth FSM. I assume Dodge is probably the same.
Poke around the 'net too. There are people who have documented original exhausts.

I mentioned placement because if its really off it can cause bad harmonics. Bad being a relative thing here. The harmonics are just one factor in an exhausts flow and sound. Definately not the dominating one as far mass flow goes. But if your going through this much effort, its something to try to get ballpark correct.

 

[383Scampman]

Like I said , if you have numbers matching , low production , true muscle car , go with factory exhaust . I had a numbers matching car once , never again .

 

[Tom Swope]

Thanks for your insight. I was unaware an H pipe was standard. Another reason to ask opinions. Car at present does not have H pipe. Anyone know correct position?

A body 383 or any other factory installed dual exhaust applications were not equipped with an h-pipe. 1968 383 GTS and Barracuda 383 dual exhaust were piped the same as the 1967 models which were quite restrictive. The flange pipes were 2.25” midway back where 2” tubing was welded in to complete the routing into the 2” inlet mufflers. The tailpipes were also 2”. The exhaust tips in 1968 were 1-7/8” O.D. and only 1-5/8” I.D. for the exhaust to exit. It wasn’t until 1969 that pipe size was increased on the 383 equipped a body cars even though the exhaust tips remained the 1-7/8” restrictive size. This was true even with the 1969 M code 440 cars which used the 383 exhaust system other than the left 017 casting exhaust manifold and the right flange spacer plate.

 

[Ccas]

H-pipe - For that classic sound and low end torque
X-pipe - for a smoother turbo type sound, less drone and more high end torque.

Almost all motors being built today feature plenty of low end torque. Therefore the H-pipe is basically for that classic sound.

 

[Mattax]

Just looked in a 69 FSM. Only shows H for 426 and 440 B-body
Location is just behind the cross member.

 

[ir3333]

the H made the exhaust quieter and allowed the factory to use less restrictive mufflers for a performance gain on the big block cars.