8.1L exhaust sizing

Hullie · February 20, 2003

I've decided that I'm either going to be going with Flowmaster 40s or Dynomax mufflers...probably the 40s. Anyway, what I'm wondering is if anybody knows the pipe size (pre-muffler) on the 8.1L big block. I'm going to go w/ a dual setup using 2 Flowmaster 40s and possibly an X-pipe. Just need to know what size 40s to order.

I assume it's 2.75", but it's too cold out to go measure

Brett

02 2500 Avalanche · February 21, 2003

It is 3 inch piping. I hope you like a lot of in cab resonance because the 40 series define resonance, believe me I know

Alex

Hullie · February 21, 2003

You don't happen to have a sound clip of your setup do you? Sounds like you have exactly what I'm thinking of doing. You have an X-pipe too? Also, you do have the 8.1L right? Don't see that info in your sig....or are all the 2500 avalanches 8.1?

Brett

gandolphxx · February 21, 2003

You could also go with the Magnaflow 12599 - dual 3" in and dual 3" out with the "X" built in - I have it on my 8.1L - very nice - not as load as the Flowmaster 40.

02 2500 Avalanche · February 21, 2003

Ya I have two sound clips on CMNTRX81's homepage but I have to find the links. I do not have and x pipe but I am putting one in very soon. All 2500 AV's have the 8.1L.

Alex

CMNTMXR81 · February 21, 2003

http://www.chevy4x4trucks.com/CMNTMXR81/

I cannot find my primitive artist's rendering of our exhaust system including pipe diameters.

However, I went two Magnaflow's stacked on end for a "true dual" system.

The stock muffler has dual 3" center in for both pipes but on the outlet side the driver's side pipe is 3" center out and the passenger side is 3" offset up out. I went with the two Magnaflow's (the one for the driver's side is 3" center in and 3" center out and the passenger side one is 3" center in and 3" offset up out) because at the time, I wanted to use the stock tailpipe. I later split them coming out of the mufflers to complete the true dual setup.

Those are the MPG files on the site with me in the bed recording while the G/F drove.

CMNTMXR81 · February 21, 2003

Also, on my site (well Chevy4x4trucks/ Jon's site) are two files named Race1 and Race2. These are MPG files of Gandolph's Magnaflow system.

Hullie · February 21, 2003

I like the sound of gandolph's and CMNTMXR81's exhausts. I'm very tempted to do the dual 3" in and dual 3" out that gandolph has.

Gandolph,

How's the sound inside the cabin? I have 2 dogs that I travel 300 miles with occasionally (not to mention the wife) and I don't want the interior noise at highway speeds to be unbearable. I do really like the sound and would be doing a dual rear-exit just like you did.

Thanks for all the info guys, very helpful.

Brett

Hullie · February 21, 2003

OK, I just got off the phone w/ one of my local muffler shops (magnaflow dealer) and he can do 1 of 2 things.

1) Magnaflow 12599 w/ dual rear-exit 3" piping

2) Spintech dual 3" in/dual 3" out w/ same piping

He can do either installed w/ labor and everything for $450. He actually recommends the Spintech because he thinks it sounds better. Anybody got any comments on the spintech muffler? I've heard some and they definitely have a unique sound..I've never heard one in person though, so I can't really give a judgement on it.

Also, what do you guys think of the price? I know I can get the magnaflow online for about $100. I don't know how much the pre-made 3" pipe go for. He said he'll be using pipes made for a X-cab SB and modifying them and extending them if necessary.

Brett

Bud · February 21, 2003

OK, I just got off the phone w/ one of my local muffler shops (magnaflow dealer) and he can do 1 of 2 things.

1) Magnaflow 12599 w/ dual rear-exit 3" piping

2) Spintech dual 3" in/dual 3" out w/ same piping

He can do either installed w/ labor and everything for $450. He actually recommends the Spintech because he thinks it sounds better. Anybody got any comments on the spintech muffler? I've heard some and they definitely have a unique sound..I've never heard one in person though, so I can't really give a judgement on it.

Also, what do you guys think of the price? I know I can get the magnaflow online for about $100. I don't know how much the pre-made 3" pipe go for. He said he'll be using pipes made for a X-cab SB and modifying them and extending them if necessary.

Brett

I just talked to Flowmaster. They say that the 530504 is made for the 6.0 and the 8.1. It has dual 3" in and out. It is a 50 series and they say it is "kinda" loud. Has anyone ever used this set up? Is Magnaflow better or quiter? I'm getting old and I don't want loud anymore!! ???

Bud

Hullie · February 21, 2003

Actually, the 530504 is dual 3" inlets, but dual 2 1/2" outlets.

If the 50-series big block sounds anything like the 70-series big block, then it's not that loud. They have sound clips of the 70-series on either the 5.3 or 6.0 chevy on the flowmaster website.

Brett

CMNTMXR81 · February 21, 2003

Under light to mid throttle mine has excessive resonance in the cabin. So much, you get a foot massage from the floor vibrating. I like that though.

However, at full tilt, it's actually quieter and the resonance goes away.

Those clips of mine were at no more than 3/4 throttle cause I specifically told her NOT to floor it this way it'd be a little louder.

02 2500 Avalanche · February 21, 2003

Actually thats not gandolphxx's AV , its mine in the two videos. It has the true dual set up with 2 40 series flows. Your wife is going to hate the 40 series, it is really loud going down the highway. You get tons of resonance up until about 3500rpm and after that its kinda quiet just like CM said.

Alex