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Old 05-06-2022, 08:50 PM
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Originally Posted by Captain Obvious View Post
One not mentioned is spin tech. Can’t speak to back pressure but they sound pretty good and don’t have any drone. That’s what RARE suggested for my system.



I can't say the source of the data, but there's this floating around the internet.

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Old 05-07-2022, 07:57 AM
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That is some of our data as well Mike. . Substitute Magnaflow for the Straightline Performance data. This is data that shipped with the CDs.
The early Spin Techs were pretty loud.

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Old 05-07-2022, 09:43 PM
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Thanks for all the replies, it helps a lot.

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Old 05-07-2022, 11:02 PM
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JMHO!83 decibel at 2200 is not acceptable for me.Tom

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Old 05-07-2022, 11:40 PM
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How were the dB measurements in that spreadsheet taken? Are those dB numbers from an engine dyno? Or inside a car with full interior? Full-length exhaust tubing? Headers?

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Old 05-08-2022, 09:42 AM
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Here is how we did it. This is the sheet we included with the CD back then. Background was controlled to the point that we got accurate measurements. We repeated the recording and testing if anything was out of place or different.
Tom Hand

Thank you for purchasing “Silent Power, the CD”.

Before you buy exhaust components, we know you would like to hear what they sound like. The sound depends upon the engine and the type of modifications done to it and the type and size of muffler and pipes used. What sounds one way on a Ford or Chevrolet may not be representative of what it sounds like on a Pontiac. Now, because of the generosity of many, this CD of Muffler sounds is possible.

We would like to share a few details about the engine, the mufflers, the exhaust system, and the recording configuration.

The engine is a 1975, 455 cubic inch Pontiac with 7K3 heads, a cast iron intake, a 750 Quadrajet, an HEI ignition, a Pontiac Ram Air Four camshaft, and three-tube aluminum coated headers.

Seventeen popular 2 1/2” inlet and outlet mufflers to fit GM A-body cars, like GTOs and Chevelles, were selected. Some of the mufflers also fit Firebirds and Camaros. Four 3” mufflers that also fit A-bodies were selected. Specifically for the Firebirds and Camaros, four cross-flow mufflers were chosen. Three of these had 2 1/2” inlet and outlet bushings and one had 2 ¼” inlet and outlet diameter bushings. Additionally, two OEM replacement mufflers were used as “references”. One is the true “Turbo-Muffler” and it is from the 1965 turbocharged Corvair. The other is a long body, aftermarket replacement muffler to fit big-bodied Pontiacs.

The engine was mounted on a fully instrumented test stand. Attached to the engine was either a pair of 3” front exhaust pipes or a Dr. Gas 3” X-crossover equipped system. Reducers were used to allow the 2 1/2” mufflers to fit on the 3” front systems. When 2 1/2” mufflers were attached, mandrel bent 2 1/2” tailpipes were used. When the 3” mufflers were being run, 3” mandrel bent tailpipes were used. For the cross-flows, special adapter pipes were made to let them fit the front systems. For crossflow tailpipes, Dynomax supplied mandrel bent, 2 1/2” Firebird tailpipes.

The microphones and sound level meter were located ten feet from the tailpipe outlet. Sound levels were measured at 750, 2200, and 3500 RPMs. Even though the sound level may sound similar on the CD, refer to the data sheets for the actual measured sound levels. On the data sheet, you will also find suggested (2001) retail prices for the mufflers, their physical dimensions, and flow ratings of them relative to open pipes of the same length and diameter as the mufflers.

We hope this CD proves useful for your future exhaust purchases.

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Old 05-08-2022, 08:23 PM
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Tom, you guys are Hands down awesome! :-) Thanks.

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Old 05-08-2022, 08:42 PM
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The Hand family has been a literal fountain of knowledge in the Pontiac world. Thanks Tom for providing this info to those of us still following in your dad's giant footsteps in making quick Pontiacs with a combination of affordable parts and diligant attention to detail.

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Old 05-09-2022, 02:18 PM
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So would it be safe to assume that the dB levels listed in the table above would be considerably lower when measured inside the cabin of a car versus 10 feet behind the tailpipes? Of course it would depend on the car, how much interior sound deadening was in it, etc.

With regard to Tom S's comment above and acceptable dB levels, I interpret the readings above to mean that 83dB at 2200rpm (for example) is not what you'd actually experience when driving the vehicle. Those are tailpipe measurements.

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Old 05-10-2022, 07:59 AM
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Quote:
Originally Posted by Tom Hand View Post
That is some of our data as well Mike. . Substitute Magnaflow for the Straightline Performance data. This is data that shipped with the CDs.
The early Spin Techs were pretty loud.

Tom, any plans for updated testing? Many new options since the "Silent Power" production, yet very little accurate/reliable testing data out there since then.

The testing you and your father have performed over the years is VERY highly regarded and appreciated by many of us.

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'67 Firebird [sold], ; 11.27 @ 119.61, 7.167 @ 96.07, with UD 280/280 (108LSA/ 109 ICL)solid cam. [1.537, 7.233 @93.61, 11.46 @ 115.4 w/ old UD 288/296 108 hydraulic cam] Feb '05 HPP, home-ported "16" D-ports, dished pistons (pump gas only), 3.42 gears, 275/60 DR's, 750DP, T2, full exhaust

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Old 10-19-2022, 07:58 PM
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On my 1968 Firebird I have Flowmaster Delta Flow 50's. These are 3-chambered with a thicker long case to help minimize drone. Here is an older video before I had the car restored:

https://youtu.be/LB1y6jtuKlU

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  #32  
Old 10-22-2022, 08:46 AM
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I had heard and read so many good things about the Dynomax large case mufflers that I had settled on a pair for my 62 Catalina. Unfortunately, they are not available in the large case, double offset inlet/outlet. I searched every brand I could think of and NONE of the common manufacturers made this case design except for the AP Xlerator stainless case mufflers. I was skeptical but ordered a pair because the size was correct. They were also reasonably priced for a stainless steel muffler. Much to my surprise after installing them yesterday and driving around for 100 miles, I really like these mufflers. System is 2.5" front to rear and it is a tight fit. Car is quiet at cruise, not raspy under power like almost all chambered mufflers and deep/throaty/but muffled at idle. Engine dyno'd just under 500 HP, solid lifter cam, 251/259 duration @.050. Idle 1000 RPM. I recommend these for street use if you don't want a really loud/raspy exhaust note.

  #33  
Old 10-26-2022, 03:12 PM
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Here are a few pics from the shop where I had the system made. I have since dressed the ends of the tailpipes and removed the stickers. This was my first time using this small old school shop. I have over the past 30+ years only used two shops. Both of them unfortunately, have either closed or the guys who were real craftsmen, have retired. This little place, called the Exhaust Warehouse in Fairborn, OH did a nice careful job and made sure everything was symmetrical and fit. He made the over the axle pipes in 3 pieces to avoid crushing them. The entire system is welded, end to end, which looks great but will be hard to deal with if repairs are needed. PM me if you want more info about the shop and could use their services. System was a super tight fit for such a huge car. Head pipes over the crossmember as stock. Very close fit to the driveshaft, very close to the speedo cable on the right and shift linkage on the left. Close everywhere over the axle to the control arms and shocks. Clears everywhere. No idea why the p;ictures are turned or how to fix them. Help?
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Old 10-26-2022, 08:27 PM
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Maybe it's an optical illusion, but the passenger side off the exhaust manifold on top looks crushed or kinked.

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Old 10-27-2022, 10:03 AM
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I see the area your looking at, I think. It looks much like the driver side which you can see better. It's where the pipe is clamped and stretched making that tight bend. Yes it is mis-shapped a little. Probably lose 1/4" effective diameter. Not allot of options there. It is not crushed. If you or someone else can turn the pics, that would be greatly appreciated. I just don't know how to do it on this forum.

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Old 10-27-2022, 10:42 AM
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It appears to be crush-bent tubing, which I'd imagine is typical of what most small exhaust shops would do. You can see similar (though less pronounced) indentations just behind the mufflers and right where the tailpipes turn down before terminating. Not the end of the world.




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  #37  
Old 10-27-2022, 11:14 AM
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Quote:
Originally Posted by ZeGermanHam View Post
It appears to be crush-bent tubing, which I'd imagine is typical of what most small exhaust shops would do. You can see similar (though less pronounced) indentations just behind the mufflers and right where the tailpipes turn down before terminating. Not the end of the world.



First, thank you for turning the pictures! Yes the pipes begin as 10' straight pipe sections. A typical exhaust pipe bender holds the pipe in a fixed position and a movable die stretches the tube using hydraulic pressure. A bender in good condition can make a 45-60 degree bend without kinking it and retain a smooth path inside the pipe. More than that, you get an inside protrusion, (kink). A typical shop or pre-bent pipes from a supplier generally don't care and the pipes are kinked internally. This gentleman, Todd, was willing to use some mandrel bent pieces I provided to get over the axle, and weld them in 3 pieces to fit properly with no kinked tubes. Is it perfect?, no. It is also mild steel vs stainless which is even harder to bend without kinking. It also cost about 1/3 of what a full mandrel bent, stainless system would have cost. I couldn't find anyone in a 100 mile radius willing to build a complete welded mandrel bent stainless system for ANY price. Pretty happy with this for an occasional use street car.

  #38  
Old 10-27-2022, 11:40 AM
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I am curious how loading affects the sound measurements. I expect the exhaust system of an unloaded engine running at constant rpm to be quieter than when accelerating.

How do these "quiet" mufflers compare when accelerating? Do some get "relatively" louder than others?

My car has glass-packs that were welded in when I bought it. If I get it running and driving, they will have to go so I'm curious. I would like it to be quiet until I wanted it to be noisy...

  #39  
Old 11-03-2022, 04:01 PM
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I've had experience with Flowmaster Delta 40's and Super 40's on my 2016 Challenger SRT392. Both mufflers had similar "quietness" at idle. But cruise, part throttle, heavy throttle and WOT were different between them. The Delta 40's cancelled out drone at cruise and part throttle acceleration, but was TOO quiet at heavy and WOT. Completely took away the car's personality. Inevitably I switched to the Super 40's. I could hear the exhaust at cruise but still without any droning. And under heavy or wide open throttle the exhaust had a deep throaty rumble.

The difference between the two products was that the Delta 40's had a smaller case and more baffles within. Whereas the Super 40 had a larger case made with thicker metal and less baffles.

The decibel level of the muffler will be influenced by the amount of noise cancellation factored into its design.

Sent from my SM-G986U1 using Tapatalk

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Old 11-19-2022, 01:44 PM
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I’m looking at muffler options for my 70 TA. I’ve heard these Black Widow Venom 250’s on Autotopia and they sound great. Very unique sound. Has there been any outside testing on them? It’s similar to a spintech or flowmaster since it’s chambered.

I’m considering the Venom 250 in 3”. My current engine makes around 660hp. Next year when it’s turbo’d it will be in the neighborhood of 1200hp-1300hp

https://youtu.be/NPhCFPeLTjQ

https://blackwidowexhaust.com/mufflers/


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