[DeTomaso] Glass Pack Mufflers

[Tony DiGiovanna]

I've got a set of Byars 180 deg exhaust on my Pcar.  The "mufflers" are
constructed like a glass pack:  There a 3" inner pipe with radial holes and
a 4" outer pipe over it.  There is no packing.  They are quite loud.  I have
adapted a set of super-trapps to the ends for street use, which are
removable for track days.  I'm just wondering what packing them would do.
Thanks for the incredibly-thorough answer.  It was exactly what I had hoped
for.  Not sure if I'm going act on any of it at the moment...I'm still
putting the whole car back together first.

-----Original Message-----
From: DeTomaso [mailto:detomaso-bounces at poca.com] On Behalf Of Mike Drew via
DeTomaso
Sent: Wednesday, March 04, 2015 9:34 PM
To: tonydigi at optonline.net; detomaso at poca.com
Subject: Re: [DeTomaso] Glass Pack Mufflers


In a message dated 3/4/15 17 04 51, tonydigi at optonline.net writes:


> So, what, exactly, is packed in a glass pack muffler, and where do I 
> get some?
> 

>>>Glass-pack mufflers are the most simple, crude kind of muffler there is. 
  They consist of an outer body, and an inner core of perforated tubing.   
The core is wrapped with fiberglass matting and then inserted into the outer
body.

Traditional automotive glass-pack mufflers (such as Cherry Bomb)

http://www.autoaccessoriesgarage.com/Exhaust/Cherry-Bomb-Glass-Pack-Muffler

are cheap, and disposable.   They cannot be serviced, and in a relatively 
short amount of time, the fiberglass packing material breaks down and the
muffler becomes nothing more than a swollen-looking straight pipe, with
comparatively little noise attenuation.

Dirt bikes and quads rely on this same technology, except for some reason 
most of them come with mufflers that are designed to be serviced.   People 
seem to think that muffler packing only lasts 40-50 hours or so, and
repacking 
dirt bike mufflers is a common thing.   Aftermarket street bike mufflers 
are supposedly good for 7000-10000 miles.   Thus, you can go to any
motorcycle 
dealership or accessories store and find fiberglass muffler packing material
for sale.

Here is a link with several representative products of the type:

http://www.motorcycle-superstore.com/motorcycle/Exhaust%20Packing

Note that most motorcycle muffler repacking kits lack sufficient material to
pack an automotive muffler, which is much larger, so you would have to buy
several packages.

Fiberglass packing material is cheap and basically disposable, making it not
particularly well-suited for use in an automotive muffler that is welded 
together.   When I gutted my ANSA GTS muffler cans, replacing the complex
and 
restrictive series of baffles and perforated tubing with a simple Y-shaped
perforated tube, I chose to use stainless steel muffler packing material, 
which is substantially more expensive and has much greater longevity.   I
got 
mine from Howe Racing, a major supplier for Trans-Am and circle-track 
racing.   It's not shown, but instead is referenced at the bottom of this
page:

https://www.howeracing.com/p-7693-2-into-1.aspx

After spending the big bucks buying from this source, I thought about it 
and decided I probably hadn't bought enough.   I then went on Amazon and
found 
this:

http://www.amazon.com/Two-Brothers-Racing-Stainless-005-10038S/dp/B000WKFNY6
/

So I bought some of that too.   I wound up using everything I had.   The 
results were quite good--my gutted exhausts are no louder than the stock
setup even though they flow measurably better.

Here is another source I just found:

http://steelwooldirect.com/muffler-packing/

So, I have to ask, what prompts this question?   I'm interested in your 
project, whatever it might be?

Mike