branj70

If i ever get my car running right again I'm going to get rid of the silent stock muffler for a Pypes M80 bullet. (Pypes makes some sick exhaust, i got em on my 'velle)

I know that after the headers, it has a 3" ORY with a cat welded on the end. But completely stock past that. The only way i can get a bullet to work, is to weld it on after the S, and before the axle. Then weld a Y just after the axle into duels and stock tips.


What size are the stock pipes? I've tried looking it up and i'm hearing every single size with no confirmations on which it is. I know it looks like a fat pipe going into the muffler, and tiny pipes coming out.

The thing is, the bullet only comes in 2.5" in/out and 3" in/out. How can this work.

RamAir95TA

iTrader: (2)

The stock intermediate pipe is 2.75". Any exhaust shop can mate 2.75" pipe to a 3" inlet.

I'd recommend getting a full cat-back system though. Might be cheaper in the long run too. You aren't doing yourself hardly any performance favors by just switching the muffler.

branj70

And all i'm looking at cost wise, is $50 for the bullet, $20 for the Y and around $100 for labor. Also I'm not looking for performance out of it, i just love hearing a v8. Plus, its only a N/A 5.7, it really doesn't need a full 3" cat back, thats too big despite what some people think. Hell, i have 2.5" true duels from headers back to Pypes Race Pros on my Chevelle and even that is plenty large

So i should go with the 3"?

RamAir95TA

iTrader: (2)

A 3" cat-back exhaust is a dyno-proven 10HP. Here is a dyno of stock exhaust versus a Borla cat-back (compliments of Keith @ WS6.com):



You do realize that dual 2.5" pipes has more flow capacity than a single 3" right? So unfortunately your logic doesn't make much sense.

Dual 2.5" = 9.81in^2
Single 3" = 7.06in^2

hitmanws6

iTrader: (20)

Used Magnaflows are going for under $200, new they are just over $300. It makes no sense to do what you plan to do. And im going with 3 inch duals on my N/A 355 so no a 3 inch catback is not too big.

branj70

I know that, i was just getting at pipe sizes in general. I'm fairly new to the F body world. I'm used to the Chevelle forums, where its either TD, X or H, and no emissions. lol.

I'm not a fan of Magnaflow. Too tame for my taste.

Most of the time going to 3" doesn't hurt, its just that you won't be pushing enough exhaust to benefit a lot from it. If you run nitrous, TC, or SC then i'd go with 3" or even 3.5" depending on your #s. A lot of the Chevelle guys won't run 3" unless they're pushing 400hp

hitmanws6

iTrader: (20)

For a y pipe setup a single 3 inch should be the minimum. And I gave Magnaflow as an example. Stay away from the Flowmaster catback. Everything else will show around the same gains you just choose based on sound.

branj70

Yea i had Flowmaster 40 series on my Chevelle and they made every single piece of trim vibrate and rattle so freakin bad at idle and at cruise. Swapped them for Pypes Race Pros dumped at the axle, and instantly 95% of the noise vanished.

RamAir95TA

iTrader: (2)

You know how to read a dyno graph, I assume?

And it's kind of funny, you mention that a 3" exhaust wouldn't be worth it, except you have a descreened MAF and underdrive pulleys.

branj70

That dynograph doesn't completely back it up; Thats showing stock exhaust vs Borla, which is a free flowing muffler.

It might be worth it on an F body or V8 with a Y pipe, however its really not with true duels. And i bought the car with those mods on it. I haven't done a thing to it except a K&N filter.

RamAir95TA

iTrader: (2)

You aren't making any sense...of course Borla is a free flowing muffler! Isn't that the point? 10HP is huge!

Then you say it might be worth it on an f-body with a y-pipe...isn't that what your original thread is about? An f-body? And modifying the stock exhaust? We're not talking about true duals for your f-body...so what does a full cat back have to do with true duals?

This thread is going nowhere, fast.

hitmanws6

iTrader: (20)

You are arguing 2 different topics. Yes 2.5 TDs will support a lot of power. But for a single system 2.75 becomes a restriction at the stock level, thats why a catback shows gains

Spiers

iTrader: (7)

Just cut your muffler off then it will sound cool

branj70

lmao, i got on to TDs now i'm all mixed up here. SO ANYWAY back on topic, thanks for the stock diameter RamAir95. And yes, i understand that 3" is worth it for an F body. It just never occurred to me that its going into one pipe instead of TDs.