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Discussion Starter · #1 ·
I've had Flowmasters on four different Chevelles, now, and never thought I'd use anything else - until now.

My last three cars were all 396 BB cars, and all had headers with 2.5" exhaust. On the first two, we installed 2-chamber Flowmasters with no crossover. On the last car, we installed 3-chamber Flowmasters with a crossover, and I thought it was a bit quieter than the first two cars.

Now, I've just finished my resto on my '71 SS 454 and we installed the same 2.5" exhaust and 3-chamber Flows with crossover, however this car has exhaust manifolds - not headers.

At a certain RPM range it resonates so loud that it is quite annoying. I never experienced this before on the other cars!

What determines how loud it is? Am I pushing that much more air thru the 454 versus the 396 that there should be a difference? Or is there something about the exhaust manifolds that changes the resonance?

I've always been puzzled by Team Chevelle members who characterized Flowmasters as too loud, but now I'm beginning to understand there may be other variables which enter into the picture. Your feedback is appreciated!

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Stan Hanek
'71 SS - 454 4 sp.
http://www.chevelles.com/showroom/stan71delivery.jpg
 

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Sorry to hear that your ears are starting to bleed Stan.
I've been where you're at right now and wound up taking them off and putting my old set of Terminators back on. My resonance problem is from turndowns before the axle. Can't run full exhaust bc of fuel system proximity to tail pipes. I'm assuming that you've got a complete exhaust system with tails, right?

They are supposed to be the LOUDEST street mufflers out there.

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502 Rat Infested 1970 Malibu - Gold Member #39
Keep America Beautiful - Drive A Brute Force Chevelle!

http://homepages.about.com/wescolby/1970bruteforcechevelle

[This message has been edited by Wes Colby (edited 03-23-2001).]
 

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Discussion Starter · #3 ·
Yes, Wes. Full exhaust with tails. Just can't figure out why this car sounds so much different.
 

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I maybe all wet with this observation but I think Compresion ratio has alot to do with the "noise" level. A freind of a freind I have gone to a few shows and hung with has a 67 SS chevelle with a 427 13:1 Compression (solid lifters to I think) motor w/headers into 2.5" pipes through single chamber Flow Masters and stock 2" tail pipes. This thing is so so so loud. His freind has the same basic exhaust sytem on his Stock 454 (maybe 9:1 compression)1971 Monte Carlo and the noise difference is like night and day

I have Flowmaster muffler on my high compression (11:1?) little 302 mouse motor and it is damn loud too.

just food for thought

Mytmouse

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67 SS396 350HP 4 sp 3:55 Posi Butternut Yellow w/Black Vinyl
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
70 SS396 350HP 4 sp 3:55 Posi, Black on Black

Mytmouse A.K.A. Robert Stacho
ACES Member # 04359
 

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Mytmouse, are you sure both cars had single chamber flows. the single chamber is like a glass pack with out the glass in it, they are stright through.
Stan, i always wondered the same thing about people thinking that flows are two loud. i have 2 chamber flows on my 355 monte, and i never though they were that loud?
 

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Yea, mine got really annoying cruzin around town. Sounded good when you got on it, and set off alarms in parking garages
, but REALLY tiresome just rollin around. Finally went back to Dynomax Super Turbos. Really like those... I think i had the 42553 FM's

FWIW, 350 w/Trick Flows, Performer cam, Stealth Intake, headers, AFB, FM Force II exh pipes

-Rich
 

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May be the exhaust manifolds.
When I had first put my new exhaust on my 65 I ran an old pair of 2 chamber flowmasters(early 90's style) that were burnt through.(headers into 2.5 inch straight pipes into those mufflers, no turn downs or tails just bare muffler ends) Before too long the local cops had busted me for noise pollution. I went down to a well respected muffler guy who does beautiful work and had my manifolds in the trunk. I said I wanted to put the manifolds back on with 2.5 inch pipes into the existing mufflers with 2.25 inch tailpipes. He said "Son, that will make your car even louder then it already is." I truly respect his opinion and went with his suggestion.(drop the flows, add super turbos, crossover and 2.25 inch tails) I don't think he was lying to me beacuse he lost money going on it that way.(switching to manifolds was 75 plus 175 for making the bends up to the manifolds adding the tails and rehanging the whole system total- 250 and the crossover mufflers and tails out the door I was at $135)
Between the fact he lost money telling me to do something else rather then what I was wanting to do and the experience and respect he has for his exhaust systems in the area makes me believe he was telling the god honest truth.
Thats why I suggest that it may very well be the fact you left manifolds on the new car rather then swapping over to headers.

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Steve
64SS-327-4spd-sold to Original owner!
65 Malibu 283/PG (Homepage)
Team Chevelle Member #71

[This message has been edited by Steve D 64 SS (edited 03-24-2001).]
 

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65SS327,

Yes I know for a fact they are single chamber flows. The guy in the 67 wanted the least restriction as possible and as much noise as possible so he made a point to show me and made me look under the car. He told me the same thing you said, that they are virtually straight through design. The other thing that I noticed is that they are smaller (in "length"...if that is what you want to call it). When his buddy in the Monte Carlo came and parked next to us later, I was gone. Later when I came back, we started talking about how loud the the 67 was after he fired it up for somebody to prove the point. The guy in the Monte tells me he wanted his to sound that way so he put them on his but it didn't sound the same. He fired his Monte up for me to prove it and he was right. It was like night and day. The Monte still was pretty loud but the 67 blew him away on the decible meter. Ever since then, I have concluded (at least in my own rookie gear head) that engine compression has a bearing in exhaust sound level. I have mentioned this in the past and expect to get challenged here on this board (and maybe help me change this conclusion) by more knowledgeable people than me, but knowbody has stepped up to the plate yet.

Another example is my 68Z with a moderately high compression 302 in it. My neighbor has a 69 Camaro with a 454 stock compression motor. We both have the Camaro Flowmaster tucked up in front of the gas tank (2in/2out pipes) with headers and 2" exhaust and people have said that mine sounds louder and different than his (can't be the judge because I am driving mine) In this case we have BBC vs SBC so maybe that has a bearing on the tone but according to others mine is louder and I then, attribute that to compresssion. As I prefaced my original post, I may be all wet but it at least sounds logical to me at this point.

Mytmouse


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67 SS396 350HP 4 sp 3:55 Posi Butternut Yellow w/Black Vinyl
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
70 SS396 350HP 4 sp 3:55 Posi, Black on Black

Mytmouse A.K.A. Robert Stacho
ACES Member # 04359
 

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i know most of you guys r older but being a younger guy thats into cars not sure if its just young but i love em loud so i went with 2 1 chamber and 3 inch exhaust.

 

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steveD, i think its intresting what you said. i was always told that headers will make your car louder. On my monte i have the factory manifolds with true duals and 2 chamber flows and its loud but its not that loud. Having no tail pipes on your car is most likely what made it so loud, because the exhaust resonates of the street and your car, and you get the echo effect. i think mytmouse has a good point and im starting to beleive thats what makes the Db difference.
 

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Mine are loud as ****. Interior noise is probably the worst at about 3000-3500 rpm. I have a 355 with around 400-450hp and 3 chamber flowmasters, the exaust exits in front of the rear axle.
 
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