How much exhaust is too much?

1967project · Jul 18, 2007

I have a 347 and two 40 series Flowmasters, 3 inch on both ends.

Is 3 inch exhaust from the collector back going to be too loud?
If it helps I have a X303 cam.
If too loud, what are the recommendations out their?
Daily summer driver, but I wake up early for work and dont want to wake the neighborhood, but still want it to sound good.

Thanks

SadbutTrue · Jul 18, 2007

I'm not exactly sure about how pipe-size correlates to noise, but how built is your 347? 3" exhausts, are usually reserved for big blocks and crazy small blocks (which your 347 could be, just don't see any information there about it).

Either way, it'll be loud but shouldnt be too bad. My 351 with headers, 2.5" pipes, and Flow 40s has never had a noise complaint from the neighbors (or anyone else) and we live in a neighborhood that I think would crack down on it if it was at all a nuisance (we have an evil homeowners association).

Someone with experience might be able to chime in on the nosie difference with 3" pipes though and overrule me.

1967project · Jul 18, 2007

Engine Specs

Holly 750 DBL Pumper
Dual Plane Intake
Angus Racing Rockers
351 Heads w/ larger intake/ exhaust
Flat Top Forged Pistons
Polished Crank
BBK Headers

The Flowmasters I have were for a 460, but never got put on.

SadbutTrue · Jul 18, 2007

1967project said:
Holly 750 DBL Pumper
Dual Plane Intake
Angus Racing Rockers
351 Heads w/ larger intake/ exhaust
Flat Top Forged Pistons
Polished Crank
BBK Headers

The Flowmasters I have were for a 460, but never got put on.

Cam specs? How aggressive are those 351 heads done? What dual-plane intake? From what I see i think you'll be better off with a 2.5" exhaust. For a small block, a 3" exhaust will only help you if you have the intake/heads/cam to rev fairly high... without those components, the reduced backpressure will just kill your torque. With a stock cam you would almost be certainly losing a bunch of torque and going slower in the quarter (not to mention drivability issues and less gas mileage... etc) with 3" pipes as opposed to 2.5". As a matter of fact, if you have a stock cam, near-stock heads, and say a performer intake, even 2.5" might be 'technically' too much...

Noise-wise I'm still not sure, but I doubt the 2.5" would be any louder than the 3...

69gmachine · Jul 18, 2007

3" = loud

I have the 3" Magnaflow system and it might as well be an open exhaust. I'm planning to change the mufflers to something a bit quieter, but still retain the 3" pipes. The Magnaflow mufflers are a straight thru design, so I'm hoping a regular "turbo" style muffler will knock the dBs down quit a bit.

69gmachine · Jul 18, 2007

3" = loud

I have the 3" Magnaflow system and it might as well be an open exhaust. I'm planning to change the mufflers to something a bit quieter, but still retain the 3" pipes. The Magnaflow mufflers are a straight thru design, so I'm hoping a regular "turbo" style muffler will knock the dBs down quite a bit.

blown65 · Jul 18, 2007

1967project said:
Holly 750 DBL Pumper
Dual Plane Intake
Angus Racing Rockers
351 Heads w/ larger intake/ exhaust
Flat Top Forged Pistons
Polished Crank
BBK Headers

The Flowmasters I have were for a 460, but never got put on.

What size engine? Assuming 302 Id say 2 1/2 is plenty since you prob wont rev much more than 6000-6500 anyways. 351 is a toss up, 2 1/2 would prob be fine but 3 might give a little more performance.

As far as being loud, depending on the mufflers you choose, the 3" shouldn't be all that much louder than the 2 1/2.

ForceFed70 · Jul 18, 2007

The sound has more to do with muffler design than the size of the piping. Generally they are louder, but that's because people with 3" exhaust piping are generally looking for every pony they can find and don't mind a little noise.

Rusty67 · Jul 19, 2007

The size of the piping used should match the HP of the engine. If yer over 400-450HP then 3" pipe is in yer future. Otherwise use 2.5" pipe. Ditch those crappy slow masters and get some good MagnaFlows.

180 Out · Jul 19, 2007

I think 3" exhaust and Flow 40's will be super loud. A 2.5" circle has an area of 4.9 sq. in. A 3" circle is 7.1 sq in. That's a 44% increase -- almost half again as much. That x303 cam will be pretty lumpy too, and maybe a little hard to start, depending on your ignition system. All-in-all, not a good combo for making friends with the day-sleepers in your neighborhood.

BTW, I'm probably going to end up with something very similar on the roller cam 302 I'm putting in my '65.

I do not understand the suggestion that a higher flowing exhaust will hurt low end torque. The latest Car Craft has a long article on dyno testing different bolt-ons, including exhaust components, and they got increased low end torque the less restrictive the exhaust system. This was with a 383 with some pretty big heads and cam, but I would expect the same result regardless of engine size.

Cyclone · Jul 19, 2007

Just an FYI, 2 1/2" would be best as you would maintain great bottom end, mid range and top end Horse Power, with 3" exhaust you will lose bottom end, your power range will not start to work until around 2,700 RPM.

I have a 308CID with AFR 2.02 Valved Heads, Comp Roller Cam 2.84 Dur. with 5.36 Lift and a 110 degree lobe center, with a Holley 750 HP Double Pumper, 9" rear-End, 3.70 Posi, and a world class trans. with 2 1/2" mandrel bent X-Pipe Exhuast with Magna Flow Mufflers.

I produced 428 on the engine dyno and 348HP on the Chassis Dyno at the rear wheels.

Note: I had 3 chamber flow masters, But They Drove me Deaf!

SadbutTrue · Jul 20, 2007

180 Out said:
I think 3" exhaust and Flow 40's will be super loud. A 2.5" circle has an area of 4.9 sq. in. A 3" circle is 7.1 sq in. That's a 44% increase -- almost half again as much. That x303 cam will be pretty lumpy too, and maybe a little hard to start, depending on your ignition system. All-in-all, not a good combo for making friends with the day-sleepers in your neighborhood.

BTW, I'm probably going to end up with something very similar on the roller cam 302 I'm putting in my '65.

I do not understand the suggestion that a higher flowing exhaust will hurt low end torque. The latest Car Craft has a long article on dyno testing different bolt-ons, including exhaust components, and they got increased low end torque the less restrictive the exhaust system. This was with a 383 with some pretty big heads and cam, but I would expect the same result regardless of engine size.

Peak torque might have gone up, but I'd be willing to bet the off-idle and really low end torque dropped. When i swapped my exhaust/headers on i noticed a loss of lowend, and thats with a 351 and 2.5" exhaust. I also noticed the top end gains.

Cyclone · Jul 20, 2007

This Is What I Have done too my Mustang, Dynoed 348HP and 416 Torque RWHP

308CID, with AFR 185 Heads ( 2.02 intake valves ) Comp Roller Cam 2.84 Duration / 5.36 Lift / 110 Lobe Center, JBA Shortie Headers, 2 1/2" Mandrel Bent X-Pie Exhaust Edelbrock RPM Air Gap Intake, 750 HP Series Carb, World Class T-5 Trans, 3.70 Posi 9" Rear-End
Front: 17" X 8" Chrome Bullitt Wheels with 225/45 Tires, Rear: 17" X 9" Bullitt Wheels with 275/40 Tires.
Baer 13" Front Brakes, and 12" Rear Brakes

Hello everyone, I am Marlon, Owner & Operator of Marlo's Frame & Alignment/Fly-Ford Racing, http://www.Fly-Ford.com I have upper control arms available that do not use Bearings Or Threads, and My Coil Spring Perches are made the same way, The car will drive like silk, because the suspension has Very Limited Friction, With NO Bind, I make these arms here at my shop, None of it is from china or some other 3rd world country which you cannot pronounce, LOL.
By The Way, My lower control arms are complete with polyurethane bushings, and both upper and lower arms come with polyurethane ball joint boots, And NO They Do Not Squeak!

The Same Control Arm & Spring Saddle Perch is Great addtion for Street Driving, 1/4 Mile Drag Racing and Road Racing as well.

Note: I have my 1966 Mustang with this same system as well as my 1969 Ford Ranchero.

My Mustang has 620lb 1" drop springs, 1 1/8" front Sway Bar, KYB Heavy Duty Gas Shocks, Global West Sub-Frame Connectors, 5 leaf mid-eye springs, 3/4" rear Sway Bar, Traction Master Bars, KYB Heavy Duty Gas Shocks.

The Ranchero has the same Suspension, except it has a 351W AFR 185 Heads & Automatic AOD Trans, and it has
Front: 17" X 9" Cobra "R" Wheels with 255/40 Tires, Rear: 17" X 10 1/2" Cobra "R" Wheels with 315/35 Tires
Wilwood 13" Front & Rear Brake System

There is an article all about them in the October 2007 Issue of "Mustang Monthly"
Marlon@Fly-Ford.com <<< E-Mail

Cyclone · Jul 24, 2007

Here is an article that I did for Mustang & Fords Magazine, Click on the link
http://www.fly-ford.com/MustangFords0404-SoundsRight.html

p0prcksandc0ke · Jul 24, 2007

too loud? no such thing

How much exhaust is too much?

1967project

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SadbutTrue

1967project

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69gmachine

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blown65

ForceFed70

That's why they call it "dope"

Rusty67

180 Out

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Cyclone

SadbutTrue

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p0prcksandc0ke

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