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Old 07-18-2009, 06:24 AM
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My Exhaust Sounds Like a Popcorn Machine

Had my new exhaust installed and it sounds like total crap!
I have a fairly stout SBC (452hp) with Headman ceramic coated long headers (1-5/8) with 3" collectors. I had 2-1/2" reducers put on with 2-1/2" dual pipes all the way to the back where we installed a pair of Flowmaster Super 44's.. Now based on all the videos I watched, which helped me decide on this system, I would think it should have a fairly deep/loud rumble/tone, especially with the large cam and idleing at 1000rpm but instead its more like a high pitch popcorn machine. ***? If I stand about 2ft behind the tailpipes they seem to blow out pretty hard and hit you in the leg with some pretty good force so is it possible I am still somewhat restricted, which is causing the higher pitch? There is no low tone at all. I did not have a H or crosspipe installed so the 2 sides are completely separate from each other.. However, I would think that 2-1/2" duals would still allow plenty of breathing room. I don't have a problem gong back and having an H-pipe installed but will this really make that much of a difference? Just don't want to waist the money if it may not be the problem. I called Flowmaster and they said its probably due to the location of the mufflers (in the very rear in a Corvette) but I have witnessed videos of other corvettes with mufflers in the rear and they don't sound this crappy.. By the way, its even worse when the motor is cold but I know its not a tuning issue because the car runs great and there are no extreme or tight bends in the pipe. The pipes are straight until they get to the rear where they go under the rear end, which doesnt require any extreme bends like going over it which is the case with most other cars.

Any thoughts?
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Old 07-18-2009, 06:33 AM
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if mufflers are on bacwards it will sound off
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Old 07-18-2009, 06:37 AM
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Quote:
Originally Posted by dawg
if mufflers are on bacwards it will sound off
The orange "inlet" stickers are still on the Flowmaster mufflers so I know they are installed the right way..
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Old 07-18-2009, 06:41 AM
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Here is a sound clip I just made.. I couldnt load just the sound so I had to add a picture and make a video out of it.. When I recorded the sound, I was actually standing behind the car and it was idling a little fast but you will get the general idea.

Popcorn anyone?
http://smg.photobucket.com/albums/v3...vetteSound.flv
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Old 07-18-2009, 07:13 AM
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Sounds about like I would expect from your description of the installation, but I did not hear any thing like popcorn popping. I I were going to put those headers on my motor, I would not choke them down into 2 1/2 inch pipes and mufflers. It would be 3 inch all the way, but I realize the challenges of doing that on a Vette.

Trees
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Old 07-18-2009, 07:39 AM
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Quote:
Originally Posted by trees
Sounds about like I would expect from your description of the installation, but I did not hear any thing like popcorn popping. I I were going to put those headers on my motor, I would not choke them down into 2 1/2 inch pipes and mufflers. It would be 3 inch all the way, but I realize the challenges of doing that on a Vette.

Trees
Here is a sound clip of a camaro with a very similar motor (SBC 355), same cam, same 2-1/2" duals, same Flowmaster Super 44's and the only difference I can find is that he has an H-pipe installed and his mufflers are located about 2ft farther from the tailpipes.. I was hoping mine would sound somewhat similar but as you will hear, there is a world of difference.. Can an H-Pipe or muffler location really make that much of a difference? Does it sound like I'm getting to much backpressure, which is causing the higher pitch popping/muffle sound?

My Car
http://smg.photobucket.com/albums/v3...vetteSound.flv

Camaro
http://smg.photobucket.com/albums/v3...t=Camaro-1.flv
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Old 07-18-2009, 09:12 AM
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Without even listening to the sound clips you`ve already found the problem. You need a X or H pipe installed. Without it, the exhaust tone is out of sync with the other, adding a H pipe balances the pressure and the sound. Also if you can lower the idle RPM it would be of help also, the nice rumble tone of idle usually comes in around 600 to 800 RPM idle. However if you wanted a real rumbly idle and a good blast while getting on it but with a lower cruise speed tone you could have dynomax super turbo`s installed and sell the flowmasters. I used to run flowmasters and got tired of the drone after a while, ever since all I use is turbo`s. Have a H pipe installed and give your flowmasters time to break in and I think you`ll be very pleased, they sound like crap when there new.
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Old 07-18-2009, 09:26 AM
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Quote:
Originally Posted by DoubleVision
. . . Have a H pipe installed and give your flowmasters time to break in and I think you`ll be very pleased, they sound like crap when there new.
that is true-i have a super 44 and it was installed about 2-3 months ago, i have noticed a change in the sound from when i bought them-much deeper now. and they dont sound quite right till the get up to temp eather.
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Old 07-18-2009, 09:29 AM
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I'm sure I'll get flamed for this but it sounds like typical Blowbastards to me! Everybody and their brother with a Mustang has them. Placement makes a difference and so does having an H or an X pipe system. Each will make a different sound and so does the size of the pipe and how many bends are in the system. How close is the system on the Camaro to yours? Are the headers exactly the same and the size and length of the pipe exactly the same too? I've been running straight pipes for years and quit spending good money on crappy mufflers that don't last and sound like crap. You CAN make straights sound good if you are willing to experiment with it a bit to find out what it takes to do it....think out of the box. Many years ago a buddy showed me his straight system on a Corvette just like yours and that's what got me into it. I was amazed at how good it sounded!
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Old 07-18-2009, 10:51 AM
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Just wondering why a 40.00 balance tube is wasting money ?

If you prefer the tin sounding idle on the Camaro.

Both videos sound very good in my opinion.
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Old 07-18-2009, 11:31 AM
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Quote:
Originally Posted by seven up
Just wondering why a 40.00 balance tube is wasting money ?

If you prefer the tin sounding idle on the Camaro.

Both videos sound very good in my opinion.
The reason I didnt have an H-pipe installed was because of the below video sound.. Its an 86 Monte Carlo with the exact same cam, heads, intake and comp ratio. He isnt running an H-pipe at all because he said he likes the sound of the individual pulses coming out at different times, which he claims makes the cam lope sound much better.. He is also running 2-1/2 pipes and FM 44's.. As you can tell, it doesnt sound that much different than the camaro sound clip I posted. I was just hoping to get more of a tin can sound like the other cars that have very similar set-ups.. If you ask me, mine sounds more like a tin can under water and much more muffled, even when the idle is down to 900-1000.. The idle on the below Monte sound clip was ideling at exactly 1000rpm.

The other reason I didnt mount an H-pipe is room.. On a Corvette with auto trans there isnt room to put any type of cosspipe until you get past the trans cross member, which actually puts it closer to the rear end (would look really weird mounting it that far back).

86 Monte
http://smg.photobucket.com/albums/v3...rent=Monte.flv
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Old 07-18-2009, 01:37 PM
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Old ears never work very well but assuming the three clips were made with the same camera at the same distance from the rear of the car, I would pick your Vette as the best sounding one but I think you are going apples and oranges in you r comparison. The length of the tubes from header and muffler must be near identical as well as the length of the tube aft of the muffler to get any where near the same sound. An H pipe just put where is the easiest to install can be a total waste of time and money. Ideally, it would be installed at the point the exhaust goes subsonic, which of course varies with RPM. An elongated X pipe provides a variable RPM range compared to an H pipe. But for your purposes an H pipe would only help you with a bad resonance problem and it normally will only change the speed (RPM) range that it occurs.

Trees
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Old 07-18-2009, 03:28 PM
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Idle speed is too high, needs and x or h pipe, believe it or not the pipes might be too straight a good mandrel bend, lateral or horizontal can make a big difference and not restrict the flow.

Just my .02
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Old 07-18-2009, 03:55 PM
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The other cars have the mufflers under/near the rear axle surrounded by a steel floor pan. Your mufflers are at the back of the car body which is made of fiberglass.

It's not going to sound the same.
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Old 07-18-2009, 04:06 PM
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You need that H pipe. Google some of the exhaust experts...Dynomax, Borla,etc..they usually have tech reports that will illustrate how different pipe sizes and mufflers will affect sound and performance....it will usually help the power curve a little too.

Straight pipes are just obnoxious and stupid....unless you have a turbo.
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