68350hp

I am toying with the idea of replacing my stock mufflers one my '74 with Flowmaster 40 series mufflers when the stock ones wear out (which will probably be sooner than I would like). I was wondering if you guys that have them are happy with 'em. Also what size do I need to fit the stock pipes. It's a '74 L48/ 4 spd.

12stepvette

I have Flowmaster 40`s on my `74....side input, center outs...I love em!! sound great and have had quite a few compliments...the only complaint I have is at exactly 1500 RPM, There is an annoying resonance that I`m sure could be cured by using a crossover pipe...I just avoid that RPM !!!

AndreG

I love my flowmaster 40's. With the convertible top up or down I don't experience the resonance, however, with the hardtop on at about 1700 RPM's I expericence severe resonance. I like 12stepvette just avoid the RPM level. Car sounds tough without being too loud. I had actually expected it to be noisier than it is.

I also do have a cross over tube but not an X pipe.

Schmucker

I keep hearing the Flowmasters don't flow well.

Stoge

I think I'm going with Borla ProXS when I decide to do exhaust work. I have heard good things about them. I have never cared for the Flowmaster sound.


[Modified by Stoge, 11:08 PM 7/4/2004]

Gordonm

I have the Delta Flow 50s on mine. I picked up 2 tenths and 4 mph in the 1/4 mile just by going to mandrel bend pipes over stock 2 1/2 and the Flowmaster mufflers. There are some that flow a few more CFM but they flow well enough for about 95% of the motors. If your up there maxing out the flow of the 40 or 50s you are making some serious HP. I like the sound, not everybody does. That is why they make different mufflers. Try to listen to many different ones before buying if you are unsure.

Sigforty

I say the only reason to by them is for the sound. They have a unique sound that alot of people like and are loud at idle, but they are not a real good performance muffler since they do not flow the best. If you are looking for a good flowing muffler I suggest dynomax, ultraflows, or hookers. I personally am running Hooker max flows on my car.

CGGorman

Ditto that on Dynomax. I'd add in Magnaflow as well.

Karfever

Hooker Areo flows...the right price and sound. Use a crossover or x pipe to give some balance to the sound and maybe a little bottom end torque!

69427

I had the same (painful!) 1500 RPM resonance with the Flowmasters. I tried the crossover thing (one by the trans crossmember, and even one under the spring before the mufflers). No change. After fifty miles I took them out and welded in some turbo mufflers. The sound quality and volume is much better. (I didn't care for that tin can sound of the Flowmasters.) The first and last time I'll buy Flowmasters.
Listen to one before you spend your money.

80TexasC3

I was hearing the same thing about the Flowmasters but I liked the sound/tone. Did my research and picked up some Delta Flow 40s which are suppose to have an enhanced technology for scavaging the exhaust. Not real sure if this works...but they sound good!

vetteonr

Flowmaster Deltaflow 40's are the way to go

norvalwilhelm

The 73 that I was changing the transmission in last week had flowmaster and they were way toooooo loud. Flowmasters require long tail pipes to sound good.
I have them on the mustang and they have that typical mustang sound, not loud, no resonance.
Use them without tail pipes and they are too loud.

LemansBlue68

The Flow master rep warned me that 40's would be loud in my Vette. He recommended the Delta 50's. I ended up just going with OEM style for now as any Flowmaster muffler will require some fabricating to get it to fit properly. I'd be interested in seeing any muffler flow data if anyone knows of a site that would have some comparison data.

Mpls Funk

Many of you have suggested listening to various mufflers before purchasing...are there places you can go to actually listen to them before purchasing? Or do U need to find someone with them installed on their car?

1970 Dave

You almost need to find someone and listen to their cars--other factors such as size motor, cam, tailpipe size, RPM, can affect the sound out the tailpipe. Would make a muffler" sound tape "a little hard. I have Dynomax Super Turbos and they are kind of a middle of the road muffler. Very nice 60's rumble to them, yet are nice inside the cabin for conversation etc. Will be coming to the Cities next month--would be more than willing to give you a listen. You can even touch her--she ain't a shy gal

SEMPER FI--1970 Dave

SuprJames

I have Dynomax on my Vette and Flowmaster 40's on my truck. The Flowmasters really sound aggressive, and that is probably the way I'm going on my '77.

Tiredol74

Flowmaster has sound clips on their website for several different combinations of cars n mufflers. I imagine others do likewise.

CGGorman

Yes, they do! It's hard to tell from a recording, though. Best bet is to try and find some examples in real-life or just start swappin'.

Around here, flowmasters are THE thing for 'Stangers and Ram drivers. Popular on Camaros, too As a Corvette owner, I'd just as soon separate myself from that crowd a bit.... Just my opinion.

AndreG

Hi folks,

Apologies for the novel but given my level of frustration and magnitude of the problems I don't think it possible to keep it much shorter;-) Reading this thread I'm starting to question some past decisions made and would really appreciate some practical experienced advice. I know enough to understand the danger of putting the words "practical" and "corvette" so close together within the same sentance.

I put flowmaster 40's on my 69 427 a couple years ago given strong recommendations from a few trusted sources which included pals, a couple muffler shops and from some reading I did on the Web attempting to better understand the concept of how scavenging works etc. I unfortunately didn't know of the forum back then and was a newbie when it came to vettes. I still read a post every once in a while such as this one on the forum and feel pretty nieve all over again. Pretty much the only thing I have been happy with since the exhaust was all redone (stock before with 2" rusty rattling pipes) was the muffler choice given I believed I had a system with very good flow characteristics and I love the loud raspy idle and exhaust sound. I am now reconsidering all this as well given comments above which is pretty much the last straw for me.

It seems anything and everything exhaust related on a C3 with a performance BB is a PITA and perhaps particularly so on my own 69. Being heavily performance orientated I expect my exhaust system to help the motor not hinder it for which I am willing to make some sacrifices others wouldn't be they monetary, resonance or clearance related given it is a toy and not a daily driver. I have ceramic coated Hooker Super Comp headers which to my present understanding should still be the best thing I can get from a performance perspective but they have SERIOUS issues with heat and clearance to the road (2.5") and the floor (.25-.75") given the 3.5" collectors right under my burning sweaty feet. I would like to drop the front suspension another inch or so but as it is the collectors already scrape all the time and I could never let anyone else ever drive the car (wife included which actually is a bummer) in the event serious damage may potentially occur. Also, they burned a hole in my floor once already which necessitated a repair and has the potential to continue ruining the floor and even burn the car to the ground. Extinguisher is always close at hand and the collector bolt flanges had to be cut off for clearance reasons with the pipes welded directly to the headers. Still is WAY TO HOT and there is no adequate space to insert any effective heat shielding. My new heads (Brodix) do not have the raised ports which would further exacerbate the problem, it is simply that I have this sewer pipe sized collector which I think is a requirement for breathing capabilities and particularly so now as I just bumped it to a 496 with the motor pushing hopefully 550 plus horsepower. The 2.5 pipe from the collector under the floor is also really tight. To not interfere with the cross member pass through on the drivers side it had to be flattened on the top to also not burn a whole in the floor. Despite how it all sounds the muffler shop actually did a good job. It all looks symmetrical, is perfectly bent and welded, there is simply not enough room for anything of necessary volume!

So, while living with this pain in the butt clearance and heat problem, I consoled myself with the thought that at least the system breathes very effectively and after all that is really very important to me. Now I'm following along on this post and I'm hearing the 40's (I think they are the Deltas? Were supposed the be THE ones to get) may actually be less than adequate performance mufflers that could be hindering flow!!! AAAARRRGGHHH!

So, off rant now. What the %^%$$# should I do with this thing? I want a kick butt exhaust system on the car, she deserves it and the new motor (15K invested) requires it. Do I just have to resign myself to spending the big bucks on hooker side exhaust for a clearance performance compromise. I'm guessing it would have to give me more clearance given the collector isn't under the floor. I heard they even with the JCL's don't flow as well as the existing full length headers with a good set of mufflers which I believed I had all along. Alternatively, is there another set of headers I can run with shorter tubes so the collector is at an angle still within the engine bay area rather than underneath the car, put in the biggest oval shaped exhaust tubes I can find that will still give me less the 3" overall tube height (even if it means being Bubba-like flattening the pipes more with a big hammer), put in a real Xpipe and different higher flowing mufflers to help compromise for the likely compromised suckier breathing headers?

Thanks all in advance!