It kind of makes me wonder when you hear stationwagons with alot less HP but same cubics make much more sound. Why is this?

 

i think its the restrictive stock exhaust and muffler. But then again no pro when it comes to these cars so i cant say thats the definitive answer. But i do agree with you, the only time my car sounds like a v8 is when you first start it up, but after that intial startup it drops down to like v6 quietness.

I'll be getting a new exhaust system soon to correc that problem!

 

You need to come to the midwest in America. 9 out of 10 f-bodys has no exhaust here. They had nature remove it for them over time. It is now an angry, loud and obnoxious dissaster that you have to listen to and grimice at the fact that they damage the f-body image. Also, not many people want to hear the full exhaust roar of the weak iron duke, V6, LO3 and LG4 cars.

 

Why are they so quiet? Laws, rules, and regulations. They aren't allowed to make them loud. From the factory, that is.

Many states have laws saying replacement systems cannot be louder than the original system. Some states actually try to enforce that. Most ignore it.

GM opted not to put louder exhaust systems on export vehicles, saving themselves the expense required to design and procure a different system for the few vehicles they exported. So, yours is quiet, too.

 

Well, I removed my muffler and cut a [ in the top. I removed all the baffels and welded it up. The welding was a problem so if anyone wants to try this you had better have a friend that is a welder. Man what a sound!! It is fantastic!! The best part is at hwy. speeds its nice and quite. Unbeliveable.

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Mine isn't so quiet no more actually. The cat is removed because it's not required by law on such old cars here. And I did a similar thing with the muffler. I cut it open and removed parts of the pipes inside. It was REALLY loud when I drove it then!! I also had some problem with the welding. Had to make it really thick to seal it up again. the sound is as you say quiet.... until you really step on the pedal

 

Exactely. Mine looked simler to that only I did open heart from the top so it wouldn't show. Great sound though.

Auggie

 

Not to disagree with Shifty, and I'm sure it's relative, but when my muffler fell off a few weeks ago, my LO3 car actually sounded pretty good with an open cat, a bit ragged at idle but really nice on the road, kind of like a (hate to say it) Mustang Cobra with good exhaust. Gotta hand it to the Stangs, their exhaust sounds pretty good. Didn't leave it like that, of course, but I wouldn't compare the sound of my beloved and perfectly running LO3 to a non mufflered Iron Duke four banger. I forgive you, Shifty.

 

right now im rollin with only a cat on the car...its loud. And i dont drive it too much, im in the middle of finishing my exhaust...soon i will have 3 inch cat, 3 inch flowmaster, and edelbrock coated or hooker jet hot coated headers

driving it with only the cat on is really loud but it doesnt seem so loud after the first 5 times driving it

 

My 2.8L v6 has always been loud and sounds really good. (purrs) After the muffler all but fell off I replaced it with a flowmaster 80s series cat-back and it sounds even better but not too much different.

 

I had this guy swear to me that if you make your exhaust too easyflowing that it would loose backpressure or something and then loose hp:s and use more gas? Is there some truth to this? ...Then why is everyone talking about getting more flow??? He even went so far as to say I should "strangle" the pipe right before it hits the muffler....? Wouldn't this just make it worse?

 

Sometime last year (I think) I removed everything behind the cat to test for an exhaust obstruction. The cat had been hollowed out long before this, but I did not know it until that day. At idle...kinda good sound, but tap the gas at all and it was way too much.

I took it for a test drive on a tool road and came to an interesting discovery: I looked down @ the speedometer and was surprised to see I was going much, much faster than I thought. The extra-loud exhaust tricked me into thinking I was moving at a much slower pace.

And as far as your question: backpressure is always a bad thing. That's a myth that's been passed around for at least 20 years here in the States. The "bad exhaust no-no" is in reference to scavenging. Basically, the design of the exhaust can help pull some of the burnt fuel/air/etc out of the cylinders while the piston is on the exhaust stroke. An exhaust that is completely open and not designed with scavenging in mind could hinder the effect. Do a search for scavenging if you want more info.

 

He doesn't know what he's talking about, that's what haha

From a performance standpoint, backpressure is bad, flow is good! After a certain point, backpressure will start to hurt you and decrease power tremendously, but SOME backpressure will move the powerband down and make it "feel" like you have more power.

I run wide open and it's a BIG difference from the flowmasters/cat setup that was on there when I got it. It doesn't feel like it has as much down low, but as soon as it gets above 2500 or so, she PULLS!

 

Referring to the backpressure:

Heres another thought, YES, you will lose power at lower rpms, BUT, you gain it at a higher rpms.

Factory cars are built for drivability, just like the 305 engine. Small bore big stroke, getting that low rpm torque and part throttle accelleration. The low RPM torque is enhanced by the small runners, small valves, and small exhaust because making the right velocities at the lower rpms.

 

so stock these cars don't come with a loud exhaust... that's weird because muffler on my car looks 100% stock and has a loud agressive V8 tone. People get suprised when I tell them it's a V6 under the hood lol

 

I checked the back pressure on my Z28 after I had it for about a year. Here's what I did. I drilled a hole just in front of the cat and attched a brass fitting and a piece of copper tubing that reached just past the pass. side door. To that I connected a plastic line used for an oil pressure gauge. I ran that line to a combo vacuum/fuel pump pressure gauge inside the car. I ran the engine to 5800 rpm and the gauge read 7.0psi. I then mounted the line between the cat and the muffler and the gauge read 1.5psi. I removed the cat and the gauge read 3.0psi.

Auggie

 

Wow! That's alot of difference. Nicely done ....But that makes me wonder why my car isn't faster than 8+ seconds 0-60mph when I have no cat either and muffler is gutted...? Could it be the bad valve seals (blue smoke at startup) that cause this sag in acceleration?

 

Yah, I had the valve seal problem too. It would start to smoke if I let it idle for awaile. Kinda embarssing. It did not however cause a loss of power but it did use oil. I installed the postive type seals on both the Int and exh valves about (4) years ago. Cured my smoking and oil loss problems compleatly. By removing the cat and gutting the muffler it did cause a lean cond. at WOT and cruising speeds. I have a air/fuel monitor and it showed a lean cond., so I richened up both the Pri's and Sec's in the 750 cfm Q-Jet. Is your engine carbed or injected??

Auggie

 

Info says LB9.

 

Was that a stock or aftermarket cat? What year car?

 

I'm sorry but I'm not much of a guru at machines.... What does this mean "a lean cond. at WOT" and "Pri's and Sec's in the 750 cfm Q-Jet"???
My engine has the TPI with MAF setup.
Does anyone know what stock horspower and 0-60 accel was reported on this kind of car?

 

Phess11, that was a stock (4) bolt cat that came on my 1984 Z28 L69.

Liquid_Metal, I guess your car is fuel injected so you won't need to know all that stuff.

Auggie

 

I am very surprised that a stock L69 cat would have that much restriction. Wonder if yours was plugged.

 

Well, you know it was only a little over a year old and when I held it up to the lite I could see a faint light and it looked good

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