Howdy

I’m building a 400/512 for the street to go in a 54 dodge pickup on a heavily modified 2wd dakota chassis. I’m shooting for low buck and fun so part of the fun is scrounging and road tripping for cheap or cool parts.

A little back story and info:

I decided to go with headers not manifolds- got some crusty NOS no name long tubes 1 7/8” I think with short 3” collectors. Unported stealths, .507/.510 cam 240°/246° @ .050, rpm intake, 750 holley, mild built 727, 2500 stall, 3.21 gear.

I was always kind of against flowmasters because not only do they never score well in dyno tests I’ve seen but every jerk in a stock f-150 around me has that sound. I always get caught looking thinking a fast car is coming then it’s just a loud truck. I know sound is super subjective but for this build I actually want that deep hollow burbling idle and a loud wot too. I don’t care too much about giving up some power or off idle torque since the second half of my gas pedal will probably feel like driving on wet leaves anyway with 500+ tq in a 3000lb front heavy pickup.

So I got a complete 3.5” used but clean welded exhaust system with a 3” H pipe and flowmasters. I think they’re 40 series? The headers have short 3” collectors I am planning to neck up to 3.5 right after them then just put downspouts in front of the axle after the muffs.

I’m thinking it should be on the loud side but hopefully a little tamer than open headers or purple hornies or something. A little drone is ok it’s not a commuter car. I’m wondering if the huge system on the mild big motor will negate the famous power robbing reputation of the flowmasters? Luckily packaging isn’t a problem in a full frame pickup truck with running boards.

Does anybody have stories to tell about the flowmaster 3.5” mufflers? 3.5” exhaust in general? Am I going to kill a ton of torque? Wake the dead? I know I won’t have the over 600hp that would call for this exhaust and bigger headers too but it was $80 delivered and cartoonishly large I couldn’t help myself!

Radar

By the way I’m posting partly out of curiosity and partly because searches didn’t turn up much on 3.5 or 3 1/2 inch exhaust stuff so hopefully the next guy searching can find this thread so comments that apply to race cars are totally welcome too- “picked up a tenth” “lost 60 foot” “perforated both eardrums” all helpful comments haha

It will sound good in my opinion...I'm in the minority here that like Flowmasters. Contrary to what you see on the internet, you'll likely not lose any power w/ them considering how mild your build is.
If they are 40 series, that's a 2 chamber. It'll definitely be noticeable, but not crazy loud.

Here's my hemi w/ 4" single chamber Flowmasters. It's definitely a lot louder than yours will be.
https://www.youtube.com/watch?v=FmOtBb4oaY8

FWIW...my old combo of a 509/292 cam, ported iron heads, 440 that ran 11.40s at 117 mph in my cuda was with 3" exhaust and 40 series flowmasters. It ran the same with or w/o the exhaust on it.

I have 3.5" exhaust on my Dart. Just a 440, Hooker headers, 3.5" collectors, and Magnaflow mufflers. I had Flowmasters, but they just were too loud. The Magnaflows quieted it down some but gave it that low note sound that the Flowmasters did not have. The Magnaflows are straight through also.

I used to have 3" H pipe exhaust, off of 3" collectors. At the time the car ran the same mph with or without the exhaust. Mufflers at the time were Hooker Aero Chamber.

Now I have 3.5" X pipe exhaust, coming off 3.5" collectors. Mufflers are Dynomax. Haven't bothered to test with/without.

Maybe both are overkill for my current power level...

I may never find out as I don't get too many chances to run with open headers.

I tried Flowmaster 40 series on my 69 Dart when I had a 440 motor and it was too loud. The exhaust dumped out in front of the rear wheels. I changed to Flowmaster 50 series and it sounded good, quiet enough not to get pulled over. I lost about 3 tenth with the 50 series mufflers over open exhaust with the car running in the high 10s. I installed a 512 stroker motor with Dynatech split flows and its quiet enough to meet noise rules at the track and so far not to get a ticket on the street. I no longer take them off on weekends at the track because the car runs into the 9s with them on and I am not allowed. I estimate that the dynatecs slow the car down about a tenth and a half. The weight is about 30 pounds.

I run 3" to the rear axle with Dynomax Ultraflows.

Pretty quiet inside the car. I do have carpet but no insulation.

I haven't tried with/without testing at the track, but I can't imagine it being very restrictive.

Are Flowmasters too loud?
WHAT???

Do it! I run 3.5 with Magnoflo. Used to run 3in 2 chamber flowmasters. Not much different. If you don't want to "neck up," I have a set of 2in primary 3.5 colector TTi headers that I'll let go for fairly cheap.

Well flowmasters are not exactly loud- more like prone to have a nasty drone on cruise. It’s the 3.5” part that would make it loud. The whole system is like half again as big as regular 2.5” stuff

469CID with 3.5" exhaust through Hooker Aero Chambers

Will run 10.90's at 4000lbs (Roadrunner)

3 1/2" for years but with Dynomax Bullets and it's loud but who cares.........

We used flowmasters on my late Bosses truck, I didn't like them but he did. I run 3-1/2" UltraFlows on my Hemi and love them.In my application they kill 117 hp, don't ask me why.

Go with a set of electric cut-outs and the rest of the questions are irrelevant. Make as much (or as little) noise as you want. And as much horsepower.

I have a set of 3.5 bullets on a set of header extension tubes with turn downs and for the street, I run a 3.0 set of Flow Masters. The bullets are really loud, and the Flow Masters are tolerable. Not much change in ET when I switched one day at the track. That's on my 605....

I ran a 3 1/2" set up on my last car for awhile. I made a unique setup by running Dyno Max Ultra flow Bullets (the short ones like 9" long) followed by a Borla XR-1 Shootout muffler right in line. It wasn't as heavy as it sounds and the XR1 dumped at the axle. I got a ton of compliments on that setup. Had a very deep clear tone and then absolutely shrieked when under full throttle.

On my sons Dart he runs the Flow Masters and when all capped up it slows the car almost 2 tenths. Just space the header collectors with a few washers and it picked up the almost 2 tenths. Its a little loud but who cares as its a hotrod.
I run the Dyno Max Ultra Flows with the full 3" exh out to the rear of the car and I really like it. Its not to loud unless you step on it pretty good. I have never uncapped my car to see if my exh slows it down any. Ron

My old pump gas Duster(518 C.I. 400 stroker motor) had a three inch system with 14x7x3.0 inch Magnaflow muffs with a side inlet and centered outlet mounted at the rear bumper. I ran it with the system on the car and ran it later with it removed, it ran 7.01 at 95.6 MPH in the 1/8 mile with it on the car and ran 6.99 at 95.8 MPH with it removed.
I swapped the heads, intake and carb.later that year and it ran a best of 9.993 in the 1/4 mile at 134.+ MPH corked up with the air cleaner on using Oregon 91 octane pump swill

I still have the 3-1/2" under my Charger with a X Pipe to 40 series 2 Chamber Flowmaster Mufflers reduced to 3" up over the axle out thru the stock tips. It has always been loud but not obnoxious & I always get a ton of compliments on how stock the car looks but idles & sounds so good. I did add some 3" cheery bombs on either side of the gas tank before the tips recently and it did quiet it down some & get rid of the drown it had around 45 MPH.

I'v had the 3" 2 chambers on my car it ran 9.49 surprising.

Just added 3.5 with x pipe to 3.5 tailpipes I am using Vibrant Mufflers Straight thru design and a couple bullets in between So 4 mufflers

Here is what it sounds like at idle

https://youtu.be/XKaz2vPYjqQ

I have 3.5" Flowmasters on Hooker fenderwell headers in my Demon. It stops just behind the doors. I have a 451" stroker.I don't find it to kill any power nor do I find it loud.

the only issue I have with the 3" system i'm running is condensation. seems like it's harder to burn the water out of the system and the mufflers rot sooner. of course there's always pro's and con's to anything and sometimes you just have to step up and try something to see how it works.

I would NOT use any Flow Master (AKA Flow Stoppers) type muffs
Get a set of straight through muffs

Time to get rid of the Flowmasters on my car. The older I get the more I feel I need to quiet it down some. As much as I drive it I seem to keep getting headaches after driving it from the noise all day. For some unknown reason the headaches seem to be worse than ever before.

Maybe it is time to go see a good Eye, Ear and Nose doctor about this
If your car was telling you it had a problem wouldn't you look into fixing it soon