vortech305

My friends 355 chevy motor is pumping in the vicinity of 420 hp at the crank, Where proud of what we accomplished doing it together. The motor is already in a 91' camaro and everything is done except for a change of rear gears and a exhaust system. My friend had heddman headers custom y pipe no cat, and a flowmaster 3 inch delta force II system and it sounded awful, he didnt like the way the guy welded the exhaust system so he litteraly ripped it off, He wants to get the mufflex system is the 4 inch mufflex system too big for a 420 hp 355 motor, im sure with that system he should have really low back pressure should he install a free flowing 3-4 inch catalytic converter to add some backpressure for some power(i heard low backpressure is not too good) what do u guys think??????????

Z28Express

If he has no plans for running a power adder, then he doesn't need the 4" Mufflex.

vortech305

so what system is best??? i mean isnt 420 hp good enough to support the mufflex system?

vortech305

anyone else??????????????????????????????????????????????

evilho7810

A 4 inch exhuast wouldn't hurt the cars performance, not with 420 horse power anyways. The only problem is with the big exhuast systems like that is you start to get a drone.

vortech305

DRONE??? could u be more specific

breathment

drone (dron)
n.
1. A continuous low humming or buzzing sound

v.
1. To make a continuous low dull humming sound: “Somewhere an electric fan droned without end”



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88' GTA 350 MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT

dhirocz

iTrader: (2)

The design of the exhaust on F bodies makes it pretty hard to get too low backpressure. Think of the 5.0 Mustang...Aftermarket kits can be 2.5" each side or more, easy. But those are duals...With both sides of the engine breathing through the same Y-pipe, I think you'll be OK. I agree with the 'droning' noise...besides that and clearance, my 3" Borla takes up alotta room!

Just run a 3" pipe and be done with it. With a 4" pipe, your restriction will still be up in the cat/ headers at that size. Would make for one hell of a low-pitched sounding engine though! 383 simulator! Lotsa rodders thought my 305 TPI was a 383 first time they heard me drive by!

jijiandfarmgang

Dual 3 inch is exhaust is plenty. Especially if you drive it on the street.
The only way to support the dual 4 would be at w.o.t.

Jim85IROC

iTrader: (2)

I don't think they were discussing a dual 4" exhaust. The Mufflex is a single 4" exhaust.


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87tpi420

i saw somewhere on this board a link to a site that breaks down the inside size of pipes in cubic inches. and dual 2.5 is actually smaller than single 4". actually 3" single is very close to dual 2.5" . as least that is how i read and understood it.
anyone else know what im talkin about?????

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87 z28 bowtie aluminum 420small block dry sump crower lt. wt. knife edged crank oliver lt wt rods brodix track 1's super ram intake slp 1 3/4 headers accel dfi art carr 700 r4 3.42 gears ssm sub frame/ladder bars.....other parts on the way ,soon to be finished!! couple more weeks!!!

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3rdgenownersoon

Mufflex also has an exhaust system that has a 3.5" diameter intermediate pipe w/ dual 3" diameter tailpipes exiting in the OEM locations. I think that would be perfect for your application. Just go to www.mufflex-performance.com and find out what you're looking for.

vortech305

well forget the mufflex system my friend ordered a single 3 inch system with a single 3 inch outlet from flowmaster, we'll have to see how that does?

88IROCs

Whatever comparisons you make regarding a large single pipe vs two smaller pipes, keep in mind the restrictions(backpressure and loss of flow) caused by the typical thirdgen exhaust. I'd be willing to bet that a single 3" exhaust is more restrictive than a dual 2" system with less bends. For the sake of ground clearance(if this a concern) you'll probably want to go with a single pipe. I'd recommend going BIG!! The myth of losing low-end grunt with a big pipe is just that,... a myth.

Probably started by someone who couldn't afford the big pipe he really wanted. Probably started the myth about an engine needing backpressure.

Backpressure is a positive pressure that opposes(slows down) the flow of exhaust gases(a bad thing).

A lot of folks confuse backpressure with the scavenging pulse(a negative pressure pulse that helps to draw exhaust out of the cylinder and helps to draw fresh air/fuel into the cylinder).

Beyond the y-pipe, the exhaust will not create any significant scavenging effects, but it will encounter significant backpressure. Go big and eliminate as much backpressure as you can.

NTChrist

Why do I run faster, consistently, with my cut-out plate on then?

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No guts, no glory.

88IROCs

Hmmm, think sniffin CO for two years might have had some effect on your cognitive abilities?

Posted by NTChrist:
It's probably not that great for him, but I had the same setup for almost 2 years. The exhaust just rusted right off the end of the cat. I can still move my limbs, remember my name, and walk a straight line. I know that CO is bad for you, but there isn't much coming in the car. After almost 2 years, I didn't smell exhaust once. Make sure there isn't a way for the exhaust to enter the cabin.

CO is odorless, and it's effects(notably memory-loss and brain damage) are cumulative over time. What amount of CO do you consider not much(prolonged exposure to small amounts for an extended period of time will have a cumulative effect) and just how did you make sure no CO was entering your cabin. By the time you smell the exhaust inside the car, you're swimming in CO.


Thinking you can break the laws of physics will not make you any faster. The fact is that increased backpressure leads to decreased exhaust flow, which leads to more burnt gases left in the cylinder, which leads to less air being drawn into the cylinder, which leads to a decrease in low-end torque, mid-range torque, high-end torque. The negative effects of backpressure increase as rpms increase(duh!).

[This message has been edited by 88IROCs (edited September 08, 2001).]

NTChrist

Alrighty. I can't argue with physics. But, this argument reminds me of the one that raged about tire size.
There was two camps in this argument. The physists that argued that because a smaller (width) tire had less footprint, it put more force on the ground, and therefore made up the difference for being a smaller tire. They even had the math to prove it, and I think we had quotes from text books flying around, too. The other camp (we'll call them "the uneducated") stated that a larger (width) tire will give you more grip.
It's unbelievable that this arguement went as long as it did. Fortunately, it was ended when some good soul pointed out that the math assummed that the tire and surface where both completely solid, and smooth (with a very low coefficient of friction). Therefore, the real world differed from the math because the tire conforms to the ground, and "the uneducated" prevailed.
I'm not 100% sure on this one. It just is odd that my car has been slightly faster while running throught the cat and muffler. I've seen a few bench racing examples that support this too.
BTW, I'm starting to doubt my first impressions on the lack of side effects from the CO. I'm starting to seriously forget things. My mom was "what's her face" the other day, because I couldn't remember "mom". I've since had the exhaust replaced.

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No guts, no glory.

[This message has been edited by NTChrist (edited September 08, 2001).]

88IROCs

NT,

Maybe I came down a bit hard on ya. But last summer when the front of the cat dropped on one of my IROCs I could smell exhaust at the first light I had to stop at. And that was with the windows up and the A/C and fan full-on. And I'd been under that car enough times, when it was on a lift, to know there weren't any non-factory opening on it. I'm thinking the fumes could have made their way in thru the shifter opening or under the bottoms of the door.