The post title says it all but Ill give some more info.This is for my wifes 63 DART 170 that will be a daily driven car with 3spd manual trans and 3.55 gears.The car will be be mostly stock with the only upgrades being electronic ign. and maybe a slight head shave(.020-.025) but would like to upgrade to a Holley/Weber staged two bbl in the future.The exaust will be full length with a turbo muffler and fully mandrel bent so collapsing the diameter through the bends will not be an issue.
Thanks
HyperValiant

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1960 Hyper-Pac Valiant(rolling test-bed)
1963 Valiant V2OO(Son's summer project,- he just turned 15 )
1972 Valiant 4dr(Daughter Kelly's repair in progress)
1974 Valiant (v8) daughter Kelly's work in progress

Although I have heard that certain exhaust pipe diameters produce the best torque I have not read anything that confirms that. Pipe size and length is important to torque when sizing header pipes but after the collector, the exhaust pipe should be as large as possible to reduce backpressure. The problem with increasing exhaust pipe diameter is with bending it to clear the axle. If the pipe is too large for the bend, it will end up flattened or pinched. However, since you are having them mandrel-bent, this is not an issue

Several years ago, Tony Lewis wrote up a performance guide for slant sixes and he recommended installing a 3" pipe. This would really be the upper limit of pipe sizes to consider. Since labor is an important part of the cost, ask your muffler shop what would be the largest pipe they could reasonably install for you.

Also, if you live in a northern climate where the roads are salted, consider putting on a stainless steel system if you are planning to keep your car for any length of time. Stainless is not much more expensive than mild steel and lasts a lot longer. I prefer T304 over T409 but T304 is not commonly available. Make sure they are using the proper stainless filler wire or rod for the welds.

Let us know what you find out.

2-1/4" pipe should suit your engine well but a 2" might preserve a little more of the 170's torque.

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"Former Owner" of '65 Barracuda, 225, Auto, MP 2bbl intake, MP cam, Dutra Duals. Presently Moparless.

Thanks guys,this car is to be a mileage machine but I would like to retain as much torque as possible so I guess Ill use the 2 inch.
Frank,I would love to use stainless but that is slightly out of my budget but I have always had good luck with aluminumized pipe and I always paint the weld joints to prevent rust.
Thanks again
HyperValiant

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1960 Hyper-Pac Valiant(rolling test-bed)
1963 Valiant V2OO(Son's summer project,- he just turned 15 )
1972 Valiant 4dr(Daughter Kelly's repair in progress)
1974 Valiant (v8) daughter Kelly's work in progress

A lot of Tony Lewis' stuff was completely baseless and right out to lunch.

A 3" pipe is far too large for a street-driven \6 (170 *or* 225). It will utterly kill low-end torque. Not only that, but there's no way to fit a 3" pipe onto the stock manifold.

Turbo muffler: Poor idea. Almost all of them set up a resonant buzz/hum/boom that will slice right through you at certain engine RPMs. Murphy's Law being what it is, it always seems to happen exactly at your preferred cruising speed. The last time I messed with various turbo mufflers, the boom came in at 56 mph and stayed until 69 mph. Useful, eh?

Loud exhausts are fun for about a week, then they get old really fast.

It's not necessary to do any elaborate calculation or buy fancy mufflers to improve upon the stock system to the max "bang for buck" extent. 2¼" headpipe, stock replacement V8 A-body muffler such as the one used on the '73-'76 318 Darts and Valiants, and 1-7/8" tailpipe. This is the setup used on the Feather Duster/Dart Lite economy models in '76, and is more than plenty of exhaust flow capacity for the 170. The smaller tailpipe does not cause backpressure; remember the exhaust cools as it travels rearward, and cooler gas requires a smaller pipe for any given flow rate. What the 1-7/8" pipe does is help keep the system quiet and keep velocity up.

Compare the above to the stock specs (1¾" headpipe, tiny muffler, 1½" tailpipe).

The individual "pulses" of the cylinders also average out somewhat (never completely) as the gas goes down the pipe and become more continuous, so the size that must accomodate an entire cylinder's charge in 1 shot isn't needed when the frequency goes up and amplitude goes down.
The only reason for any restriction in size (since this is not a tuned length or collector) is to prevent back-flow (reversion), and the relatively small size of the manifold outlet already does that (the gas is travelling too fast to change direction and back up all the way to the valve). If the existing outlet is too large for the motor (no experience here), then a restriction will help.
However: the restriction is still the smallest size in the system, whatever and wherever that is. If the manifold exit is 2", using any larger size cannot change that bottleneck and will have no effect on power, but will reduce the pumping loss quite a bit. Isn't the final outlet size of any exhaust system infinite (to the atmosphere)?

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Exactly what does the V-8 muffler sound like? My D-150 has the stock exhaust (minus the cat. convertor) and it sounds pretty cool. Is a truck muffler the same as a V-8 muffler? Do flowmasters resonate at cruising speed. How about a glasspack?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

My opinion: Flowmasters and glasspacks are crazymaking on a slant-6. The V8 stock muffler doesn't really sound like anything; it keeps noise down to a tolerable level *without* any RPM-dependent loud zones.

The MagnaFlo I bought sounded awesome at idle and low speed (nice 'n' "rappy") but drove me absolutely nuts between 56 and 69 mph on the highway. VOOOOOOOOOOOOOOOOOOOOOOMMMMMMMMMMMMMM!
Adding a resonator did NOT help.

Glasspacks? Please. Only if your house is up on blocks and your fridge is on your porch and your truck has a gun rack.

On the other hand, there are http://www.pertronix.com/exhaust_products/smithy.htm Smithy's Steelpacks. If you get the 30" length, it would probably not exhibit too much RPM-dependent boominess while still sounding "cool".[/url]

Resonance caused by muffler design or RPM is tough to figure out, but sometimes it's just where it's hung. Moving a bracket a few inches, or using a longer hanger or rubber biscuit sometimes makes a big difference.

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[quote="SlantSixDan"]

Glasspacks? Please. Only if your house is up on blocks and your fridge is on your porch and your truck has a gun rack.

My F-150 has glasspacks on it and it sounds great. AND NO my house is not on blocks my fridge is not on the porch and my truck does not have a gun rack.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Count me in as a glasspack lover to. Unless you're going to build up your engine lots with 110 horsepower and a reasonably sized pipe you don't make a lot of racket, I'm betting this would hold true even up to 140 HP.

Er...there's no relationship between the amount of horsepower your engine produces and the type or amount of sound it produces.

Isn't it the case of the more horsepower you produce the more air you're sucking in and expelling(and more gas consumed). If you're building power NA style it seems like it be very true, the turbo would be different because the turbo acts like an exhaust gag.

None of this is necessarily true, no. And there's no relationship between the amount of horsepower your engine produces and the type or amount of sound it produces.

There is definitely a difference in sound as cylinder pressure increases. Making more power is usually associated with higher firing pressures.The rpm where max pressure is produced will also be important. The buzz you get at certain RPMs has more to do with where max pressure is produced than the muffler you use. Using a balance tube will broaden your torque band and help with drone or buzz.

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Yeah....Im the one who destroyed this rare, vintage automobile.....