[69-CHVL]

We'll, since I gained about 100hp, my "just right" 3"x18" Magnflows have now become officially stupid loud. Its tolerable when driving around, but at WOT they get this unbelievably loud "rap" or crackle that is just ear-splitting. Draws way too much attention.

What's my options? I don't wanna spend too much $$$ - this will be the 3rd set of muffs in 3k miles. Does the Hemi turbo come in 3" off/off?

 

[Shawn Gilbert]

Hooker Maximum flows were the quietest all around muffler that i tried on my 600HP SBC and they flow very good.

Give a set a try i think you might like them, they are relatively cheap as well

 

[vrooom3440]

One thing to keep mind is the larger the muffler the more noise attenuation in general. Which is why rather than the recommended 14" basic muffler length I went with the longer 22" Hooker Aerochambers. Costs more but...

You can also consider adding a second muffler/resonator back in the tailpipe on each side for more sound attenuation. I figure this is a good spot and application for a glasspack if mine is too loud.

 

[GRN69CHV]

Pretty sure Dynomax does have the large case turbos in a 3 x 3 configuration. I take it the driveshaft came in, will have to hear it this weekend. Funny thing, you've commented that my car is loud from a mile away, it has the 2.5" HEMI turbos. What you are experiencing is a combination of a lot more cam, exhaust port flow and the biggie in sound, a full point of compression. Getting the compression upwards of 10/1 makes a huge difference in a motor.

 

[69-CHVL]

Joe,

I was thinking about your situation too. I just saw on the Summit sight that Dynomax has a 3" x 20" super turbo. Wondering if that's quiet enough.

Thanks for the Hooker suggestion.

The quieter the better AFAIC.

 

[mr 4 speed]

Those 20" case super turbos and 2.5" tails would make it quiet.
Whats another $100 for Flowmaster tails

 

[GRN69CHV]

Got the DYnomax sheet in front of me. I have the 2.5x2.5 20" case #17748 side/center on there now. Best fit it really side/side. 3" is part # 17770. Maybe I should look into these myself for the new 3" head pipes I have here. I was planning on keeping the 2.5" tails. Here's what is interesting. Dynomax lists the HP rating for the muffs. My current side/center 2.5" muffs are rated 378HP / pair based on a flow of 415CFM each. The 3" 17770's are rated 512HP / pair based on a flow of 563CFM each. Not to get off the topic, but Vince has been with me on several WOT runs with my new motor. Motor pulls incredibly hard in the midrange and although it revs to 6K, it kind of goes flat. Have to wonder if the 2.5" exhaust system is really choking it? There may be a good 50+ HP waiting in the exhaust system.

 

[69-CHVL]

Joe, if your car is that loud w/20" case muffs, were going to be in trouble w/the 3"x20" case. Are you sure the 20" is the case and not the overall measurement?

 

[RATtyCamino]

For what it's worth guys, the quietest exhaust I've heard in an application like that is the hemi turbos w/2.5 tail pipes. I'll be using the Super turbos with mandrel bent 3" all the way...but I like the noise.

 

[69-CHVL]

When Joe had the 2.5 system/dynomax hemi's w/the 396, you couldn't hear his car. Put a 500HP 454 in there and that same exhaust system is now too loud, which means it will be defeaning in the 3" version.

 

[RATtyCamino]

When Joe had the 2.5 system/dynomax hemi's w/the 396, you couldn't hear his car. Put a 500HP 454 in there and that same exhaust system is now too loud, which means it will be defeaning in the 3" version.

Yeah, I know what you are saying. That's why I said quietest. I don't know if you are going to get any of these beasts really quiet. My last malibu had mandrel bent head pipes into two flowmaster 2 chambers dumped before the axle. I guess one man's loud is another man's rediculous!! Another option you have is using a primary set of mufflers and just adding an additional set of true Helmholtz resonators like all the factory cars have now.

While not a true resonator, these would probably work:

http://store.summitracing.com/partd...&N=700+4294922711+4294804382+115&autoview=sku

Good Luck,
Bill

 

[vrooom3440]

If you would like some interesting reading... you could look for the timeless book "Scientific Design of Intake and Exhaust Systems". I discovered this book back in high school and it was old then, being originally published in 1962.

It suggests that sound attenuation drops significantly when the muffler chamber volume is too small compared to the cylinder size. Considering the general use of 14" small case mufflers on performance exhaust systems it is probably not a surprise that they get loud. The muffler volume is being overcome by the BB cylinder size. Didn't Chevy originally use a much longer (and thus higher volume) muffler on these cars?

Another interesting tidbit of info was that a glasspack type muffler gave a 26% sound reduction but two glasspack type mufflers in series gave a 61% reduction. This supports my previous suggestion of an after muffler.

The book also supports the use of smaller tail pipes for sound reduction.

 

[GRN69CHV]

Mine are the 20" case.

 

[69-CHVL]

Kjett came to the rescue with a set of 22" case straight-through jobs - look like Magnaflows. Hopefully this will get things under control. I just took my car for a drive and boy do my ears hurt!

 

[69bu]

Kjett came to the rescue with a set of 22" case straight-through jobs - look like Magnaflows. Hopefully this will get things under control. I just took my car for a drive and boy do my ears hurt!

How does it run? Any full-throttle blasts yet?

 

[69-CHVL]

Low end feels the same so far...I guess that's good since I added 20* of intake duration. I stood on it once briefly and it felt like the car lifted up the power hit so hard. But I need to get about 500 miles on this clutch and trans before I can do full blown WOT blasts.

We'll see.

 

[Guest]

You can add hollow shoe-boxes in front of the mufflers just off the collectors that work like expansion chambers that will help kill the sound..

Or as Steve said run short glassspacks for use as before and even after muffler resonators too!

And the '73 Duece and Quarter Q-Ship guys have even been known to "Y" each side and run DUAL stock Hemi mufflers side-by-side w/ full big tailpipes to make one almost whisper quiet for going out on Sat. night and running for say $500/drag...............

I've said many time's that I figure installing as MUCH W/D/T smooth perforated inner pipe glasspack bodies down each side butted end-to-end will quiet one AND it will be 100 percent STRAIGHT-THROUGH!! For almost ZERO backpressure!!

pdq67

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[69-CHVL]

I was thinking about adding additonal muffs, but there's no way anything would fit AFTER the muff, these pipes are too tight as it is. Some glasspacks in front of the muffs may be an idea though.

 

[Chief fat nutz]

I have around 450-475hp with my little 355 or maybe more with the addtions of last month but Im running 3" into Aerochambers with 3" tails. Not the quietest............but I just bought Hooker Maxflow mufflers that are 3" but 22" long! I remember having their maxflow style 14" case mufflers on my 455 pontiac and it was very quiet for 400+hp. Ran mid 12's and was very quiet.....sounded like it ran high 14's by the tone of it idling with these mufflers:thumbsup:

I want quiet so I bought those 22" long case Maxflow mufflers,I'll post a clip if I can of before and after.

 

[3pedals]

if your car does not have full tail pipes and a H pipe, or X pipe I would start there. theese both substantially reduce noise. I run Ultraflows and they seem very reasonable nois wise.