To Flowmaster Or Not To Flowmaster...

[MountainMan]

I am wondering if anyone has used a Flowmaster 17342 on a 2003 Z71 Avalanche, and if so, have you been satisfied with it? I am a weekend bass fisherman and use the AV to tow my boat. Any thoughts? I have been reading the other posts and am still not getting the impression that people are using the entire Flowmaster Exhuast System, just bits and pieces. Any insight would be great....Thanks!

 

[RichUF]

Lots of us are changing out just the muffler for a Flowmaster. Results and opinions are as mixed as the different sounds that the different models produce. Performance change seems to be subtle without other modifications. I did mine for the sound.

Some do change the other pipes behind and/or in front of the new muffler, and some do entire change from the cat back. Depends on what you want. I'd suggest reading advice from muffman, 11H, and a few other that seem to know a lot about this topic.

Good luck

 

[tractman]

Muffman has done a lot of testing with different combinations and he has posted what has worked the best. Try the threads under Exhaust. There is a ton if info there....
I think he offers advice particularly for those who tow.. Good luck

Tractman

 

[RichUF]

Without trying to take any of muffman's thunder (I couldn't if I tried)...

The quick and dirty for Flowmaster without having to go search is: FM70 series, without resonator, single center in, dual 2.25 out, side exit. Also replace pipe in front of exhaust with 3" if you want. Oh, yeah, and have a competent, custom shop do the work. Then mod the intake to get your low-end torque back after the exhaust change.

This is just what I've read here. I'm sure I'll get scolded and corrected if this is totally or in part incorrect

 

[Billy3sticks]

Just as an example...I cut just behind the cats and went 3'' out the back to twin #40 series.

I've been more than please with not only performance, but the beautiful sound that only a Chevy can make.

GoBot

 

[txyank1]

I've been more than please with not only performance, but the beautiful sound that only a Chevy can make.
GoBot

I thought I'd never get the smile off my face when I put my 1st FM on. An '88 Chevy Sportside 350 5spd. Sounded just like a 'Vette!

 

[bonedog]

Just as an example...I cut just behind the cats and went 3'' out the back to twin #40 series.

I've been more than please with not only performance, but the beautiful sound that only a Chevy can make.

GoBot

You have true duals on DIZAM!!!!! Did you go 3" all the way? Might have to look into this as I already have 1 DF40 on

 

[Billy3sticks]

I've been more than please with not only performance, but the beautiful sound that only a Chevy can make.
GoBot

I thought I'd never get the smile off my face when I put my 1st FM on. An '88 Chevy Sportside 350 5spd. Sounded just like a 'Vette!

Txyank1,

I can only imagine

The closest I ever came to that was a "hush thrush" system on my Chevy Laguna S3...That had a 350 cid with 350hp...The only complaint was it was to quiet for me.....I needed more noise

GoBot

 

[RichUF]

I thought I'd never get the smile off my face when I put my 1st FM on. An '88 Chevy Sportside 350 5spd. Sounded just like a 'Vette!

The old 350's sounded better, IMHO

 

[Billy3sticks]

I thought I'd never get the smile off my face when I put my 1st FM on. An '88 Chevy Sportside 350 5spd. Sounded just like a 'Vette!

The old 350's sounded better, IMHO

Rich,


I totally agree....They sounded like they really had a pair...if you know what I mean

GoBot

 

[txyank1]

The old 350's sounded better, IMHO

I agree. But something I did notice with my '99 4.8.....the engine screamed like the Chevy's of old. The 5.3 never sounded like that, (still doesn't) but the first time I wound up the 4.8 I thought "dam that sounds good". Then I put an Airaid on and it was....."whoa, sounds like a 4bbl kicking in"!

 

[muffman]

Very nice Rich

No lecture for you today....heh

However, I believe what he was asking was our opinion on a particular Flowmaster kit, the #17342.

Ok, about this kit. It is the dreaded "American Thunder" kit. Take note of the "thunder" part of that name. Although they try to tame the 30 series muffler, with a resonator, this kit is still a loooooooser. It also uses 2 1/2-inch tailpipes (tooo big for a 5.3L), which will contribute to additional resonation.

Additionally, the kit you are talking about has a list price of $593.95, although you can find this cheaper most likely on the Internet, but it is still just an aluminized system.

Also, don't forget to read this thread, if you are considering rear exit tailpipes:

http://www.chevyavalanchefanclub.com/cafcna/index.php?board=107;action=display;threadid=20546;start=20 (not my spelling here...)

Cheers

 

[kwinsor]

Are you looking for sound? Performance? Both?

Dual exhaust, without an "X" pipe is a real performance killer. It may work on a huge engine at wide open throttle but on a small displacement street engine it's going to ruin our nice flat torque curve.

One key to good performance is to keep exhaust gases moving quickly. A big pipe or two big pipes seem like they would help but it's just the opposite.

A bad example would be making a pea shooter out of 1 inch diameter pipe instead of a soda straw. How about an ounce of water out of a squirt gun compared to a garden hose.

When the idea is to keep things moving quickly the pipe needs to match the pump.

Another big deal with true dual exhaust. On a small engine it's like having 2 four cylinder engines instead of an V8. Our firing order switches from left side to right. With a single or "X" pipe the exhaust pulse on one side helps move the pulse on the other side. True duals kills this and kills low end torque. To make things worse, our firing order switches from one bank to the other throughout most of the order but then has 2 firings on the same side. Without an "X" pipe, that's a long dead spot in exhaust flow at low RPM.

Do it for the sound but there may be a way to get sound and performance.

kw

 

[MountainMan]

Thanks for all your input on my output question. I have found a local custom exhaust house that has done several AV exhaust systems. The recommendation of the shop owner is similar to the repsonse that I got from muffman. I am going to put a FM 70 series and use 3" pipe to a "Y" and go with 2 1/4 tailpipes set on the side behind the rear tires. I will keep you updated once the work has been completed.

Thanks Again!