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540" BBC Alum. BMP Merlin X, F-1R Procharger, 12-rib [email protected], 11psi, AFR 357 heads, E-85 '86 Camaro
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Discussion Starter · #1 ·
I have the headers built and have the oval tube for the side tail pipes pretty much planned out. Based on the room available for mufflers (about the same on both sides), what would you make the internals look like to get some noise reduction, even if it meant sacrificing some HP? I see factory muffler cutaways focus on sending the exhaust into and out of perforated tubes, sometimes with roughly divided chambers without any packing. I've had Flowmasters on the car and have cut them open to look at the 'delta' design and have seen Spin Tech cutaways as well. So far I'm thinking the shape leans towards 2 chambers with a connecting tube (2nd picture) to get a few sudden velocity/pressure changes to occur, then maybe add some obstacles in each of the chambers or pockets of perforated stainless with stainless packing behind them. All guessing though!

The engine is a BBC 540, Procharger F1-R, 2.25 primaries to 3.5 merge to 4" secondary. (What looks like bullet mufflers in the CAD below are just the flex couplers.)
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Have you ever done back to back passes from open headers to with the mufflers? Think they cost you any power?
Yes sir I have .15 is the cost. Some due to the weight, these are a little heavy. When I called SpinTech I told them I wanted something with a good sound and minimal HP loss. I really am happy with em. Only If I knew how to post a video 🤷🏻‍♂️
 

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540" BBC Alum. BMP Merlin X, F-1R Procharger, 12-rib [email protected], 11psi, AFR 357 heads, E-85 '86 Camaro
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Discussion Starter · #6 ·
Define ‘noise’. If you want to eliminate drone, look at resonator design. Mufflers change the tone.
Good question, I'd say I'm most interested in reducing the volume overall as opposed to drone concerns. So if sound level meter 50 feet away would record a lower dbA number, that is the goal. I'm not necessarily trying to get under any specific track noise level limits, but would like to attract a little less attention while idling and cruising.

I’m very happy with my 4” oval spin techs. I think they sound pretty damn good. My exhaust setup is similar to yours. 600” NA street/strip 1040hp.
Chevelle-Guy, that looks like about a 9" x 13" muffler, is that about the size?
 

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Good question, I'd say I'm most interested in reducing the volume overall as opposed to drone concerns. So if sound level meter 50 feet away would record a lower dbA number, that is the goal. I'm not necessarily trying to get under any specific track noise level limits, but would like to attract a little less attention while idling and cruising.



Chevelle-Guy, that looks like about a 9" x 13" muffler, is that about the size?
Dang close to that. These are 8.5” x 14.5”
 

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For most sound reduction youre going to need a offset muffler with packing in it that redirects exhaust as it travel through the muffler. Any straight through design whether perforated or not will still be loud. The issue is with high horsepower stuff is that the packing seems to burn our quickly. I have a pair of Borla Pro XS on my car and went with 3" to try and quiet it down since I do drive it a lot. What Ive noticed is they have got progressively louder as the packing has burned out. My car will shoot flames on the two step and that has accelerated the packing materials death. I also was limited on room under my car so I couldnt go with a big muffler, but youll want to get the biggest you can possibly fit in there for the most volume reduction as well. All said and done when driving on the street a lot like I do in a car with 1000hp, you wont even notice a 50hp difference on the street. Unless youre doing some sort of street racing on a road that actually hooks. From about the point of 750rwhp all I notice is my car spins more the more I turn it up where I have less useful power . Because of that Im redesigning my exhaust system to try and get a bigger muffler or possibly 2 small mufflers on each pipe.
 

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I am not a spintech fan, but exhaust sounds are purely subjective. What some people like, others hate, so no matter what route you chose, there is no sure fire way to ensure you'll be happy. Flowmaster also makes a slimline designed muffler, and i have actually cut the backplate off the muffler, and water jet cut a new back plate with a round outlet, as rotating a flat exhaust tube is pretty much impossible. I only needed the flat tube in front of the muffler. I also made the header exit oval, so there was no transition required. Both ST and FM's are restrictive, but if you look at the designs, ST is more restrictive, but as said, on the street, you're not going to feel the difference. I prefer the FM sound over the ST sound.
 

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I am not a spintech fan, but exhaust sounds are purely subjective. What some people like, others hate, so no matter what route you chose, there is no sure fire way to ensure you'll be happy. Flowmaster also makes a slimline designed muffler, and i have actually cut the backplate off the muffler, and water jet cut a new back plate with a round outlet, as rotating a flat exhaust tube is pretty much impossible. I only needed the flat tube in front of the muffler. I also made the header exit oval, so there was no transition required. Both ST and FM's are restrictive, but if you look at the designs, ST is more restrictive, but as said, on the street, you're not going to feel the difference. I prefer the FM sound over the ST sound.

Accurate and well said.
 
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