i have a 75 dart /6, 225, holley 1945 1bbl and i recently got out a hacksaw and cut off the catalytic converter and just for fun dropped everything and tossed it.
im going to take her to a muffler place, what should i have them put on so i can get maximum power out of her? she is my everyday car, back and forth to school, work etc, no racing.
i have heard a few people talk about 2 1/4" pipe, is that the optimum size? what about muffler types?
thanks

If you're keeping that set-up I'd just bump up to 2-1/4 pipes and a flowmaster or other free flow muffler. Otherwise, I'd take the opportunity to slap on Dutra Duals and have them fabricate a 2-1/4 single pipe union or go all the way and have a dual exhaust all the way back.

You will get several opinions on this around here, all of them with their own merit....and cost....

OH NO!! You sawed up and tossed the exhaust pipe from your 1975 Dart? Shame on you! Do you realize the 1975 cars are the only year A-body that came with a stainless steel exhaust pipe from the manifold to the muffler?????

I tried a 2-1/4" pipe on my 1975 Valiant. It was too noisy/ resonated. Maybe a 2" would be quieter?

The 1974 exhaust pipe is one piece from manifold to muffler. The exhaust shop that made the 2-1/4" pipe for me (20 years ago!) used the bend card for the 1974 pipe but used 2-1/4" pipe instead. Some of the bends were too close together for the larger pipe and the guy was skilled enough to know how to reposition the pipe in the bender to make the bends come out right.

I took the pipe home and bolted it into the car. It fit! Many years later when I installed a manual transmission in the car in place of the automatic I found that the clutch linkage would not clear the 2-1/4" pipe.
I had to reinstall the original pipe.

Pretty sure Craig is kidding about the stainless headpipe; the factory parts books show no different P/N for the '75 vs. '76 headpipe and I've never seen a headpipe, even on a '75, that a magnet wouldn't stick to.

There's no such thing as "the" optimal exhaust setup. Each and every car is different, and everyone's priorities are likewise different.

Not sure why Craig got abnormal noise with the 2-1/4" pipe he tried; lots of factory installations have 2-1/4" headpipes and even more aftermarket systems have that pipe size without abnormal noises. Muffler selection is just as critical as proper pipe placement and anchorage in avoiding undue noise.

The factory high-flow exhaust used in the '76 Dart Lite/Feather Duster (and in the 225-2bbl cars starting in '76) consisted of a 2-1/4" headpipe leading into the same muffler used with the 318 V8 models, and out the back via a 1-7/8" tailpipe. Stepping down in pipe diameter after the muffler is not the gross performance-killing no-no that it might seem to be; remember, exhaust cools significantly as it moves rearward in the system, especially as it goes through the muffler. Cooler gas occupies less volume for any given mass flow, so for any desired flowrate, hotter gas needs a larger pipe than cooler gas. Smaller endpipes also greatly reduce noise and resonance.

I haven't tried every muffler out there, and there have been some developments in the field, but my experience with "high performance" mufflers has generally been that they sound fun for a week and then the fun wears off and they become annoying...especially when they have a resonant drone that'll cut right through you at 55 to 65 mph. I tend more towards the philosophy of using a stock type muffler, but in a higher-capacity version intended for an engine larger than mine. This closely follows the factory prescription for greater exhaust flow without irritating noise.

Dutra Duals are a fantastic idea, especially in a post-'67 "wide body" car in which there's lots of room to put together a nice system.

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Too many people who were born on third base actually believe they've hit a triple.

Nope, Craig is NOT kidding about the stainless head pipe. I still have the pipes from my 1975 Valiant. The pipes are perfect after all these years of Minnesota winter road salt. The hangers and the flange things (don't know the proper name) where the head pipe and cat pipe connect to each other are rotten because they are made out of plain old steel.

Here is scan from 1975 factory service manual.....



Remember, 400 series stainless steel IS magnetic and will get a brown rusty looking surface color to it and fool you to think it is not stainless steel. 300 series stainless steel is not magnetic and stays shiney unless it is in contact with other iron which will make a rust stain on it.

Now on my 1976 Valiant the head pipe is aluminized steel and rusted through where the hanger touches it by the rear transmission crossmember. I brazed that hole shut for now but in the future may need to install the stainless steel pipe from my 1975 Val.

Right, I don't understand why I had the noise problem either. I am aware that the Feather Duster/Dart Lite and certain Volaré/Aspen models used a 2-1/4" pipe. I do know that the muffler I tried for a 360 Volaré/Aspen was a definate NO NO, it had mega resonation/droan at highway cruise speed. That 360 muffer had 2-1/4" in and out and I stepped down to the stock tail pipe.

Having just completed my super six upgrade. I also went with larger pipes after having read many posts in the Slant Six.org

I did not want to be loud, just kind of nice as my 69 GTX was back in the old days....

So I found this place called Accurate Exhaust products at the Chrysler Nationals in Carlisle, Pa last year. Over the winter I ordered the 2.25" left side of the exhaust for a 340 Dart from the muffler back including the chrome tip. I had my local garage cut my original pipe off just under the drivers front bucket seat. From there the guy custom bent a 2" pipe pretty close to the path of the original pipe was. It was fit into the 340 muffler and from there back it is 2.25" and out the tip.

When I purchased my stuff, I also included the original hangers in stainless. I am pretty happy with the results so far.

At an idle it has quite a rumble to it. Not loudness but tone. It makes people turn and look to see what it is.

When driving the car it has a nice rumble under 35 mph. over that it quiets out and you don't have to turn up the stereo or yell at your passengers...

At a local show in Bath, Pa for fathers day I was parked next to a 69 340 Dart and as I was leaving the lot, you couldn't tell what I had under the hood.

My first long trip will be to Harrisburg for this years Chrysler show at Carlisle. I will let you know how loud it is at 60 -65mph

Here is the web site address if you are interested
http://www.accurateltd.com/

Matt

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67 Dart GT convertible
"225 Slant 6"
Super 6 and 2.25" exhaust.