new 392 but old exhaust

[rebel65]

hey all.


so i know this must have been answered but i tried searching for it and i just ended up with a bunch of searches that had nothing to do with what i searched for.

anywhoo. got a new 351w stroked to 392 with the prettiest things possible that no one will ever see ( hopefully ) lots of cam, AFR 185 heads with the big valves. and some killer headers.

what i want to know is is there a reason to go 3". because i'm not revving over 6500 on the engine and i can't find 3" mandrel bent tail pipes lol.

is 2.5 for a 500 hp engine that doesn't rev too high good? or is 3" actually going to help performance wise?

thanks and sorry if it's been answered to death take care.

 

[stonecoldtx]

hey all.


so i know this must have been answered but i tried searching for it and i just ended up with a bunch of searches that had nothing to do with what i searched for.

anywhoo. got a new 351w stroked to 392 with the prettiest things possible that no one will ever see ( hopefully ) lots of cam, AFR 185 heads with the big valves. and some killer headers.

what i want to know is is there a reason to go 3". because i'm not revving over 6500 on the engine and i can't find 3" mandrel bent tail pipes lol.

is 2.5 for a 500 hp engine that doesn't rev too high good? or is 3" actually going to help performance wise?

thanks and sorry if it's been answered to death take care.

Magnaflow has a complete 3" "Header Back" mandrel bent kit with an "X" pipe that includes 3" mandrel bent tailpipes . . . you might want to check them out . . .

 

[rebel65]

yea, and it's also absurdly expensive. $655 + shipping is way more than i want to spend on a kit. although it is stainless which is nice.
the summit universal kit is 90 bucks.

i can get the summit 3"universal kit,summit cutouts with summit electric cutouts, flowmaster mufflers, some glass pack resonators, and still have money to get it welded before i even get to $600.

but what i am mainly asking is if 3" pipe the whole way is too big. + i don't like the magnaflow mufflers as much as flows..

 

[stonecoldtx]

yea, and it's also absurdly expensive. $655 + shipping is way more than i want to spend on a kit. although it is stainless which is nice.
the summit universal kit is 90 bucks.

i can get the summit 3"universal kit,summit cutouts with summit electric cutouts, flowmaster mufflers, some glass pack resonators, and still have money to get it welded before i even get to $600.

but what i am mainly asking is if 3" pipe the whole way is too big. + i don't like the magnaflow mufflers as much as flows..

I think you can get the 3" Magnaflow kit from Performancepeddler.com for something like $498 shipped . . .

Also, it's my understanding that the Magnaflow mufflers are quieter than the Flowmasters

I'm using the 2-1/2" Magnaflow kit, but I'm replacing the "X-pipe" with a dual inlet/dual outlet Magnaflow "X-Flow" muffler, and am using a set of 20" body, 2-1/2" offset inlet--2-1/2" center outlet DynoMax Super Turbo mufflers, and am adding a pair of DynoMax 12" X 2-1/2" Race Bullets to the upper portion of the tailpipe as resonators, and a set of resonated 2-1/2" oval tips (I have a '70 Mustang, and they used oval tips that year).

I am using a set of Patriot Ceramic Coated shorty "Clippster" headers that have the collectors located at about the same place as the original exhaust system.

I've got a pair of 90-degree pipes welded on each side of the inlets of the Magnaflow muffler in an "S" shape toward the front of the car.

I've finished welding up the pipe from the header to the Magnaflow muffler on the right side, and have to finish the left side now.

Once I get the left side done, then I'll mount the muffler, tack the pipes to the "S" curve pipes I've welded onto the muffler, and then place hangers at the rear of it to support it, pull it off the car and weld it all up.

The connection between the Magnaflow dual inlet/dual outlet and the pipes to the SuperTurbo mufflers are Flowmaster ball joint connectors, for ease of pulling the exhaust to remove the trans if needed. I've already welded one portion of these connectors to the outlet side of the Magnaflow muffler, and will weld the other side to the pipe that will go to the SuperTurbos.

I will be cutting the original muffler hanger mounts from the reproduction mufflers, and welding them onto the back of the SuperTurbo mufflers, and since the difference between them and the original mufflers was only 1", they should fit right up with no problems.

I'll probably just clamp the tailpipes to the SuperTurbos, but I'll weld in the Race Bullets in the location where the original resonators on these cars went, and then probably clamp on the tips at the rear.

By the time I get done, it should be relatively quiet, but still have great flow and a good tone to it.

You might be able to do the same thing with the 3" Magnaflow kit, get a 14" long dual inlet/dual outlet "X-Flow" with 3" Inlets and Outlets, and use a set of DynoMax 3" inlet/outlet SuperTurbo mufflers like I am to quiet it down.

At least it would flow really well, and it would be as quiet as you could possibly get it with 3" pipe, especially if you put a set of 3" DynoMax Race Bullets in the tailpipes and get a set of resonated tips like I am . . .

However--it ain't cheap! I will have something like around $830 including a set of new collector adapters after selling off the two Magnaflow mufflers that came with the kit.

I already had the dual inlet/dual outlet Magnaflow, but I bought it several years ago and just had it laying around, but I think I paid something like $85 for it, and it's included in the price I listed above.

If you want it quiet, you're probably going to have to do it similarly to what I have done, but if you like a little louder, then you can eliminate some of the steps I have taken . . . maybe just add the SuperTurbo mufflers--it might be quiet enough for your taste with those on there, and you could get it done for around $500 after selling off the mufflers that come with the kit like I did, and whatever it will cost to get it welded up.

 

[htwheelz67]

you arent going to see a huge difference in a good high flow 2.5 system and a 3" system except a huge difference in noise. You may see 10hp at extreme top end. I have a 408 and I am going to use FRPP dual mode muffs, I have borlas now, I may add some electric cutouts for when I wanna really draw attention.

 

[rebel65]

stonecold, thanks for your thoroughness lol. i'm not such a granny really.. : ) the main reason that i want a somewhat quiet ride is so i can put cutouts and later invest in electric cutouts to go on em, and have every note under the sun. i want to roll up to a light sounding stock and make a vette **** himself when i hit the cutouts.

plus i want to take it out of the garage without waking the whole block... well i only have 1 neighbor but that isn't the point.

that seems like quite the amount of resonators tho in your exhaust i would totally love to hear it sometime. it makes me being worried about having too many myself trivial.


the whole setup i was thinking of was my headmans to a resonator, x pipe, cutouts, flowmaster delta 50's, then to the out in case i want some extra quieting. don't get me wrong i ran around town in my 289 with flows cut off after the muffler, no turn downs or anything:| I LOVED IT.. ears rang after a while tho .

btw, aren't magnaflows just fiberglass packed? every time i heard a flow 40 next to a magnaflow they always seemed so much louder than the flows.. i donno tho.

what i really wanted was some flowmaster deltaflow 50 bigblocks. but those fers are HUGE sound so damn good tho..



so what i got away from this thread. 3" for louder, 2.5 gives me tons more options on doing stuff cheaper lol.

 

[Rusty67]

2.5" exhaust starts to become a bottleneck somewhere around 450hp. That being said, it depends on your power curve. If you are never making it to 6000+ RPMs then I don't think you need to step it up to 3".

Magnaflows flow WAY more then Flowmasters. I would definately go with the Magnaflows, especially if you plan on going with cutouts at some point. The Magnaflows will come alive at higher RPMs tho, trust me.

 

[rebel65]

i would be putting the cutouts before the magnaflows or flowmasters would be, after a resonator so i don't think i would really be concerned about flow too much at least for the cutouts.

 

[zookeeper]

I may be wrong, but doesn't cubic inches play more of a role in deciding exhaust size? It's still under 400 cubes, so although I'm sure it's a stout motor, I would think the 2.5" would be fine. Having said that, lots of new trucks seem to have huge exhaust, so maybe bigger would be better if you have the money.

 

[Rusty67]

I've seen motors that are 3.0 with Turbos pick up 50HP when going from 2.5" to 3" exhaust. A small block V8 will usually only need 2.5" but if it is heavily modified, 3" could definately be a benifit. Forced induction can easily put the need over the top for 3".

 

[bnickel]

for the system on my cougar with a mild 351w i plan on using either 2.25" with dynomax "hemi" super turbos or going to a 2.5" system with a set if hi-flo universal cats, a set of 24" or 30" glass packs (resonators) before the "hemi" turbo muffs. both systems will use a rolled lip quad exhaust tip like the 69 GT and Mach 1 used. i'll probably use the univ. cats on either setup actually just to keep down the exhaust smell old cars usually have. in fact i may do the systems identical regardless of whether i go with 2.25" or 2.5" exhaust. i have 2.5" with regular dynomax super turbos on my mustang right now and it's just a little too loud for my tastes, really. i like to be able to sneak up on people from behind without alerting them to my presence from 1/2 a mile away..... i also haven't decided between stock manifolds or shorty headers either, for now i'll probably stick with the manifolds and decide on whether or not to use shorties later on.

i've also considered using the 2.25" system with some of the patriot variable flow glass packs (as the resonators) and cutouts after them running to a 2.5" or 3" system that dumps in front of the diff. that way i could vary the sound of the smaller system and also be able to bypass the small system completely. if i go this route i'll run 2.5" up front until the patriot muffs and then 2.25" the rest of the way out.

 

[Justin01]

2.5" exhaust starts to become a bottleneck somewhere around 450hp. That being said, it depends on your power curve. If you are never making it to 6000+ RPMs then I don't think you need to step it up to 3".

Ditto. Unless you put a blower on it, a 2.5" will take you up to about 500 bhp.

A blower motor is a different ball game too. I had a 1.8L turbo VW and jumped to 3" exhaust and saw about a 20-25 gain aside from the tune.

 

[stonecoldtx]

for the system on my cougar with a mild 351w i plan on using either 2.25" with dynomax "hemi" super turbos or going to a 2.5" system with a set if hi-flo universal cats, a set of 24" or 30" glass packs (resonators) before the "hemi" turbo muffs. both systems will use a rolled lip quad exhaust tip like the 69 GT and Mach 1 used. i'll probably use the univ. cats on either setup actually just to keep down the exhaust smell old cars usually have. in fact i may do the systems identical regardless of whether i go with 2.25" or 2.5" exhaust. i have 2.5" with regular dynomax super turbos on my mustang right now and it's just a little too loud for my tastes, really. i like to be able to sneak up on people from behind without alerting them to my presence from 1/2 a mile away..... i also haven't decided between stock manifolds or shorty headers either, for now i'll probably stick with the manifolds and decide on whether or not to use shorties later on.

i've also considered using the 2.25" system with some of the patriot variable flow glass packs (as the resonators) and cutouts after them running to a 2.5" or 3" system that dumps in front of the diff. that way i could vary the sound of the smaller system and also be able to bypass the small system completely. if i go this route i'll run 2.5" up front until the patriot muffs and then 2.25" the rest of the way out.

bnickel, I've got the same philosophy! I understand and can appreciate a nice sounding engine, but I don't feel like it necessarily has to be LOUD to accomplish that!

The setup you describe doesn't sound that much different than the one I'm working on right now, except instead of using 24" or 30" glasspacks, I'm using a pair of 12" Race bullets and a Magnaflow "X-Flow" muffler in the center; I'm using a set of 12" resonated tips and you're using a pair of catalytic converters.

It would seem that both of our goals are pretty close--to have as good of flowing system as possible, and have it be as quiet as possible.

Stealth is GOOD!!

 

[Rusty67]

If you are going to run cats then go 2.5" all the way out and convert down at the very end where the tips are. With a set of magnaflows, cats and 2.5" exhaust, it should be rather quiet until you hit 3500 rpm.

 

[rebel65]

yea that's what i am looking for in this 392, i want a good flow, but not excessively loud. i mean i like how the car sounds loud from 20 feet away, but when sitting in it all i am doing is vibrating lol. hear all the parts of the car vibrate that no one outside that says "Hey that sounds awesome!" hear lol. plan to dynomat but i figure ditch the old 2.25 that is really just a hack job that's been hacked up.

so i think i'm going to do this 2.5 inch all the way, resonators either before or after the summit X pipe, to cutouts before the flowmaster delta 50's then the 2.5" flowmaster mandrel bent tail pipes.. those things look sweet. i might add some resonators somewhere.. maybe those bullet ones after the muffler since i don't really care if it gets even quieter. i just want to hear the sound of the engine. : )