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Custom Exhaust Questions
https://www.slantsix.org/forum/viewtopic.php?t=46012		 Page 1 of 3
Author:  jrdoj [ Fri Aug 19, 2011 10:49 am ]
Post subject:  Custom Exhaust Questions
I recently installed a 2bbl intake (and exhaust - off the same super six engine) on my '68 Dart 270. I wasn't even sure if the factory exhaust pipe would mount to the new manifold, but it does, so I bolted it up temporarily until I could get it in for a custom exhaust. This week I took it in for an estimate on the custom exhaust job and they quoted me $300 - this included the 2 1/4" pipe and a Flowmaster muffler.

Today, I read this thread...

http://slantsix.org/forum/viewtopic.php ... ics#115191

...which provided some insight, but made me wonder about a few things.

1. When I was underneath the car with them during the estimate, I asked how they would go about mounting the exhaust pipe to the manifold. (I thought maybe they would hack off the exhaust pipe mounting flange, bore it out slightly, and weld the 2 1/4" pipe on.) But she told me they would have to leave a short sleeve of the current pipe on and mount the 2 1/4" pipe to that. That struck me as shoddy, and after Dan broke down the "physics" of the acceptable pipe diameters as they relate to what point on the system (in the above link), I had to wonder what the point of this job would be if they went about it in such a way. I mentioned that I had upgraded to the 2 bbl system, but maybe I didn't make clear that the exhaust manifold was of a larger diameter (it is, right?), making this response partially my fault.

2. The Flowmaster muffler. Is this a good choice for someone (me) who wants a little 'sound', but doesn't want to be obnoxious? It's like a cocktail - I don't want the taste of my liquor to be overwhelming, but I like to know it's there. Or will this produce the unwanted freeway noise? What might be a better choice?

3. Is $300 a fair price? It's a locally owned shop.

Thanks for the input.
Author:  SlantSixDan [ Fri Aug 19, 2011 12:02 pm ]
Post subject:  Re: Custom Exhaust Questions
Quote:
she told me they would have to leave a short sleeve of the current pipe on and mount the 2 1/4" pipe to that. That struck me as shoddy
Yup. Shoddy and lazy and schlock. Don't use that shop. New 2-bolt flanges to accept whatever pipe diameter are utterly standard custom-exhaust pieces.
Quote:
I didn't make clear that the exhaust manifold was of a larger diameter (it is, right?)
No. All slant-6 exhaust manifolds have a 2" outlet. There is nothing such as a "2bbl exhaust manifold".
Quote:
The Flowmaster muffler. Is this a good choice
I wouldn't pick it! Loud exhausts are fun for a week, then they get really old in a big hurry. See various thoughts and opinions on the matter here.
Quote:
Is $300 a fair price?
Not for the halfassed work they propose to do, no. Go elsewhere.
Author:  Joshie225 [ Fri Aug 19, 2011 12:11 pm ]
Post subject: 
If the shop won't get a new manifold flange and build off that I'd go somewhere else. You really want and need the flange and pipe to be slightly larger than the manifold outlet. This was not the case in 1968.

The exhaust manifold outlet on a Super Six isn't any larger than the older manifold, but the Super Six exhaust pipe and many truck/van pipes is larger. You need the larger pipe.

There are several different Flowmaster mufflers. Most do not provide for quiet, relaxed cruising. How do you want the car to sound?

Here is my old '67 Valiant with full 2 1/4" single exhaust and a Walker Dynomax Super Turbo muffler. http://www.youtube.com/watch?v=g4fv0N3LvAw
Author:  jrdoj [ Mon Aug 22, 2011 10:48 pm ]
Post subject: 
Just as I suspected. Thanks for the input. I'm going to look around for another shop.

Selecting a muffler, just looking at Flowmaster, I'm leaning toward the 40 series (with "Delta Flow", I guess). But I'm going to investigate other brands. I want a nice putter from the outside, but don't need/care to hear it while in the cab.

I thought I'd seen prices for this job at or below $200, so I'll assume $300 is the ceiling.

Josh, you've helped me out before, which I appreciate. Dan, I've followed your advice in other threads many times before, so it was nice to hear from you firsthand. Enjoy the rest of your summer, gentlemen.
Author:  raPoM [ Mon Aug 22, 2011 11:00 pm ]
Post subject: 
If you dont want to hear the muffler in the cab, do not get a 40's series flowmaster. If you have to have a flowmaster,go with a 50's series. I have had a 40's flow,and it is not a tame muffler,I have not tried a 50's series,but I hear good things. I am prob. going with a stock type replacement to cut down on noise.
Author:  slantsixbob [ Mon Aug 22, 2011 11:48 pm ]
Post subject: 
I've had both the 40 and 50 series flow master, the 40 isn't too awful loud, i like it myself. the 50 series has a really subtle rumble to it, you wont hear it going down the road unless you get into it a little. as far as price goes i paid 300 for custom work, he made the whole set up for me. made a custom connection (lack of a better word because im tired) to hook up to the manifold did mandrill bends as well, brand new hangers all around as well. sounded great, no clearance issues and i was happy with it. guess i got lucky. also fully agree with josh and dan. good luck on it
Author:  Jljde [ Tue Aug 23, 2011 5:14 am ]
Post subject:  Re: Custom Exhaust Questions
Quote:
No. All slant-6 exhaust manifolds have a 2" outlet. There is nothing such as a "2bbl exhaust manifold".
So would it be feasible to just run it as 2" from the front to back with a 2" i/o muffler near the end?
Author:  SlantSixDan [ Tue Aug 23, 2011 9:23 am ]
Post subject: 
The muffler needs to go in the stock location. There's no space on an A-body for an end-of-tailpipe muffler placement.
Author:  Old Car Scott [ Tue Aug 23, 2011 11:47 am ]
Post subject: 
I've always wondered but never asked, what is the best muffler for performance vs. noise?

Like the OP said in his original post "It's like a cocktail - I don't want the taste of my liquor to be overwhelming, but I like to know it's there"...

I do realize this question is somewhat like asking "What is the best flavor of ice cream?" but maybe someone could point out something that is a nice compromise. 8)
Author:  Jljde [ Tue Aug 23, 2011 11:47 am ]
Post subject: 
Quote:
The muffler needs to go in the stock location. There's no space on an A-body for an end-of-tailpipe muffler placement.
Understood. I meant "near the end" as in wherever it is now, but I'm a bit vague sometimes.

My uncle has a lift, so I think I should be able to do the exhaust stuff myself. :)
Author:  SlantSixDan [ Tue Aug 23, 2011 12:11 pm ]
Post subject: 
Quote:
I've always wondered but never asked, what is the best muffler for performance vs. noise?
As you already understand, that question cannot be answered with other than opinions. If what you're trying to do is to reduce exhaust flow restriction to a practical minimum cost-effectively without creating a noise nuisance for yourself or others, the answer is a stock-type muffler, but a larger-than-stock one. The stock slant-6 muffler and headpipe were much smaller than optimal for the simple reason that smaller pipe and mufflers cost Chrysler less than bigger ones. See thread I previously linked for discussion of muffler selection.

The key phrase is "practical minimum". By picking a "performance" muffler sold as such -- a Magnaflo or a Dynomax or a Flowmaster, etc. -- it is certainly possible to reduce exhaust flow restriction below levels attainable with a larger stock-type muffler. But unless you are racing and turning very high RPMs, the extra flow capacity will be of no practical importance because you'll never use it, but you will have paid for it in extra dollars and/or extra noise.
Author:  olafla [ Tue Aug 23, 2011 4:19 pm ]
Post subject: 
Hi Jljde. The subject has been discussed several times, you could use the search function to find many opinions on muffler choice.

One post on flowmasters, from this thread:
Quote:
I work at a muffler shop and before that, i thought that all flowmasters were loud and obnoxious. that was until i was educated on how flowmasters work and how they are supposed to built. the FM is a "scavenger" muffler, so if the exhaust is built right, the muffler will actually start to pull the exhaust out of the engine resulting in better economy and power. the secret to making a FM work is to put a tailpipe that is at least 18" long and to use one size smaller pipe for the tailpipe. for example, if you have a 2.5" pipe from the header/manifold, run a 2.25" tailpipe to the bumper. the resonation and the drone will not happen. the reason the smaller tailpipe works is Physics. as the exhaust gas gets further from the engine, it cools and contracts. in order to maintain gas velocity through the system, you have to go to a smaller pipe, which also helps keep the exhaust flowing through the pipe and not tumbling out.
I put a FM 50 on my wife's Subaru Impreza and was amazed by the difference in how the engine ran and how the car drove. it is no louder than stock, picked up 1-2 mpg, and made a big improvement in bottom end. what i did was to upgrade the pipe from the cat to 2.25" and put a 2" tailpipe on it. the exhaust does not resonate and there is no drone whatsoever. all this is what i have learned from my boss who was educated and trained by FM in the 80's.
Olaf.
Author:  SlantSixDan [ Tue Aug 23, 2011 4:29 pm ]
Post subject: 
Testimonials involving cars that don't have slant-6 engines (or at least some kind of inline-6) are not really relevant; inline-6s have particular exhaust noise characteristics that are more difficult to silence than other kinds of engines. Also, every Subaru Impreza ever made has a catalytic converter, which itself substantially quiets the exhaust before it even gets to the muffler, making that testimonial even less relevant to the Dart in question.

Moreover, the notion that "the muffler pulls exhaust out of the engine" is, ummmm...let me try and think of some diplomatic terms. "Imaginative", "creative", "certainly a good effort at marketeering". It's nice handwaving, and it sounds cool, and I'm sure it sells Flowmaster mufflers, but I also doubt it's the slightest bit true unless the Flowmaster people have figured out a way to sidestep the laws of physics. There is certainly such a thing as scavenging, but TTBOMK mufflers don't do it.
Author:  slantsixbob [ Wed Aug 24, 2011 2:21 am ]
Post subject: 
IIRC, mufflers are do exactly what they are called, they muffle the sound of the engine, the interior design of one is made to pretty much cancel out the excessive noise an engine makes naturally. (if you've heard an engine off the headers you can appreciate this).

as dan said they dont "pull" exhaust from the engine. although they do help flow better once the exhaust makes it there.
Author:  wjajr [ Wed Aug 24, 2011 5:14 am ]
Post subject: 
At best a muffler won’t obstruct flow, at worse it can greatly restrict flow. Flowmaster’s, unlike their name, are not the best flowing muffler on the market. Give this article a read top to bottom for an explanation of exhaust system theory, I think you will find it interesting.

As for Dan’s statement inline sixes have special needs in the muffling department, he is correct. The wrong muffler, will make an I6 grate on one’s ear, and be unbearable after a short time. Currently I am living with such a beast equipped with twin twenty year old Sonic Turbo mufflers… They are gaud awful on the ear, well my ear anyway.

Currently I’m looking for a Sonic replacement; without being able to hear most manufacture’s mufflers behind an I6 is making selection of a new muffler difficult.
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