Shortly after I get my Duster, I'm planning on having the Feather Duster (2 1/4" pipe) exhaust done up with a Flowmaster 50 series muffler, and at some point in the near future I intend to install a Super Six setup. Will the Feather Duster exhaust be sufficient for a Super Six, or should it be larger?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Feather duster exhaust = 318 V8 exhaust = Super Six exhaust: A 2¼" headpipe, a 4¼" x 9¼" oval muffler with 2¼" inlet and 1-7/8" outlet, and a 1-7/8" tailpipe.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Woops forgot about the 1 7/8" tailpipe.

So I guess it'll serve me just fine then

Edit: d'oh, can't find any mufflers with a smaller outlet (unless it's a dual outlet) than the inlet. OH well, I figure a 2.25" outlet ain't going to hurt anything...

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Feather Duster Exhaust is NOT V-8 exhaust (in fact the last 318 A-body I pulled the mill out of had some pretty small pipes - almost like the stock 1 barrel slant pipe)...it's pretty close to what Dan lists as the 'Super Six' pipe...except he forgot the mandatory catalytic convertor... The larger outlet will kinda make things a bit 'raspy' in the upper end (but not really any louder than the local Honda crowds' fart cans...)

You might see about a 2.5" pipe (if they are 'bending it' with a forming machine the bends will knock off/restrict the pipe 1/4" due to the dies used), and necking it down to 2" at the muffler....(that might be more common...).

-D.Idiot

I'd go with a 2.25" in and a 2" out muffler.

The muffler might do that, or just get a 2.25"/2" reducer.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

My Super 6ed Valaint has 2.25 from end to end with a turbo type muffler....no "buzz" and plenty o flow. The 2.25 in/out turbo muffler was the cheapest option.

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

Yeah, it is. Same muffler (2¼" in, 1-7/8" out, with same part number), same tailpipe (with same part number)...only difference is, obviously, a Y-pipe for the V8 and a headpipe for the slant-6.
Given that the last 318 A-body was made 31 years ago, who knows what aftermarket pipework you could've been looking at?
...which was changed to the 2¼" headpipe, 1-7/8" tailpipe configuration for 1976...
...which was not factory-installed on all 225-equipped cars in North America until 1979...

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thought I would tell you what we did on our 63 Valiant.It has the 2 1/4 head pipe, then it splits to a Y pipe after the trans.It has duel flowmasters. and duel stainless tips that are 2 1/2. It gets loud from 55 to 65, but the noise drops off before and after that.Besides, the 40 series just sound great at an idle.
Just my 2 cents-Kidd

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Wife's: 64 Valiant
My: 70 Road Runner, 67 Barracuda, AND the 62 Valiant drag car!!

How are the 40 series for interior noise? I've got a single 50 series Flowmaster on my truck, which has just a slightly larger L6 in it (and 2.5" pipes with no catalytic converter), and on the highway I can hear it fairly well. I'd like to have something that flows well but stays pretty quiet on the road. I will also be Dynamat-ing and Lytherm-ing the snot outta the car, so maybe a couple 50 series would be best for what I want?

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Just remember, Dynamat is heavy. You will be adding significant weight to the car when you do that. If you don't mind that, it's good stuff for sure.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

You ain't lyin'. I put two bulk packs in my truck and when they came to my folks' place via UPS it was a grunt for me to carry them into the garage! I have no plans to race the car though, so the extra weight won't bother me. I do want a clean, comfortable, quiet ride though.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

Also, beware of generic substitutes for Dynamat. Some of the cheaper stuff has a tar-like material instead of the stuff Dynamat uses and it will melt and run when it gets really hot. Real Dynamat won't. That's probably not as big a concern in the Northwest but it would be a real problem in the Southwest.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Another reason I'll only use Dynamat or Lytherm. Lytherm's Zero Clearance stuff is great for dealing with engine and exhaust (even catalytic converter) heat.

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'74 Duster w/ HEI ignition, beat to snot suspension, A904, 8.25" 3.55 SG rear, still being tuned up and gets 17 MPG

Know how they always build a better idiot? That's me

The Walker super dynomax hemi mufflers work pretty good and are reasonably quiet with a nice sound. They list them as a "Super Turbo", just look for the longer case. They last a long time and have a lifetime warranty. I have used 2" mufflers and had the shop swage them up to 2.25" for 2.25" pipes on v-8 cars. It is quieter than a 2.25" muffler and still flows real well. You could just open up the inlet to 2.25" and run a 2" tailpipe for the slant. This is the exhaust I plan on putting in our swinger. I may try a Hooker Aero chamber as well. I had them on my GN and for an open chambered muffler they were amazingly quiet with no drone. Louder but sounded good, not like an open exhaust dumping into a 55 gallon drum in the trunk. Best performing mufflers I ever had on that car. Nothing like the noise of a flowmaster on one of those cars.