Chevy Astro and GMC Safari Forum banner
1 - 7 of 7 Posts

·
Registered
1997 GMC Safari SLX - AWD
Joined
·
58 Posts
Discussion Starter · #1 ·
I have a bit of a head scratcher here.

I have always wanted a tad more sound from my vehicles. So when I bought my Safari months ago, I thought about the muffler right away haha. I don't want anything TOO loud (I had a Thrush 2 chamber 17651 on my Jeep 4.0, a copy of the flowmaster 40, and it was too much haha), so I thought it would be nice to get something like a Flowmaster 50 Series. It is shorter and lighter than that stock lead weight under there, so for offroad, a bit better too!

My question is as follows.... I know that the factory muffler goes from 3inches, to a 2.5 inch tail pipe, which I assume is for back pressure (?). I have read on here that it would be stupid to run a full 3 inch exhaust, as you would lose torque.... the Jeep XJ I owned was the same concept.

So here is the headscratcher: Would you run:

1. A 3" inlet / 3"outlet muffler, with a 3" --> 2.5" step down after the muffler

OR

2
. A 3" --> 2.5" step down on the pipe in front of the muffler, and then run a 2.5" / 2.5" muffler?


I am fairly certain each one gives a different result due to muffler volume, gasses going in/out, and back pressures.... or am I nuts, and it's a case of "6 of one, half dozen of the other"?

Anyone who has done a flowmaster or similar welded performance muffler... which route did you take?

Thanks !
 

·
Registered
1997 GMC Safari SLX - AWD
Joined
·
58 Posts
Discussion Starter · #4 ·
Thanks for the input folks! Alright, so I suppose get the 3" muffler, and then drop down to the tail pipe section. The reason I was confused is that the OEM boat anchor muffler has the 3" inlet and the 2.5" outlet.... so I was curious where the restriction happens. Just on the outlet, or somewhere internally.
 

·
Registered
1997 GMC Safari SLX - AWD
Joined
·
58 Posts
Discussion Starter · #10 ·
All very interesting and knowledgeable replies! Thanks folks!

One thing I did not quite get from all the tech talk ...... and forgive me if it all went over my head a bit, but a stock 4.3 in my van.... that would NOT benefit from a full 3" exhaust right? A 2.5" pipe after the muffler should suffice?

I only ask because I have a bunch of 3" mandrel bent pipe from a silverado laying about that could easily be turned into a muffler-back tail pipe for the Safari but that may be totally pointless (and may drone anyway). Cheap isn't always the answer, just because I have it on hand doesn't mean I need to use it!

And agreed on the comment about Flowmasters.... No thank you, to a welded muffler on a daily. Had one on my Jeep XJ.... holy drone.
 

·
Registered
1997 GMC Safari SLX - AWD
Joined
·
58 Posts
Discussion Starter · #12 ·
these are inexpensive better flowing then stock and sound decent no drone: Exhaust Muffler-Soundfx Direct Fit Muffler Walker 18274 | eBay They come in other sizes but this is for the idea just search sizes
Thanks! Appreciate it. My main idea for the muffler isn't sound, that's for sure. I am OK with a quiet/moderate system... I just want to get rid of that Trash Bin sized OEM muffler underneath haha. It's a hazard off road and just so HUGE. Just tidy up the underside of the Astro a bit
 

·
Registered
1997 GMC Safari SLX - AWD
Joined
·
58 Posts
Discussion Starter · #21 ·
Sorry to be bringing this thread back to life but...... I have been scouring mufflers and I scored a deal recently on a muffler for about 75% off the shelf price (clearance).

My issue is that the muffler is an OFFSET IN/OFFSET OUT set up. And from crawling under the van, seems my 1997 Safari is Offset IN/Centre OUT

Would it be that far of a stretch to think I can use the one I bought on my van with the factory pipes? I mean obviously only I can determine this by measuring/doing that mathemagics..... BUT has anyone run that setup?

Thanks!
 

·
Registered
1997 GMC Safari SLX - AWD
Joined
·
58 Posts
Discussion Starter · #23 ·
Plenty of room under these vans.. the offset is irrelevant.
Any muffler shop can make it work.. you should be able to as well.
Appreciate the reply ! I figured there is "wiggle room" under there, but I just wanted to make sure I won't be encountering any problems others may have run into.

Seems like the ol sawzall will be putting in work soon! haha
 
1 - 7 of 7 Posts
Top