how do glass packs work and whats inside them? a friend told me if i hit them with a hammer to break the insides, they get nice and loud with out havign to break them in over time, is this true?

I think overtime they get crappier by the day and the sound is not to good, just going by assumption though :?

i wouldnt use a hammer on the glasspacks, they will burn out eventually, i dont know how long but they will, now if you wanna burn the fiberglass out of em now you can do somethin ive done before and thats spray the inside of em with wd40 or somethin similar and it will smoke a little but will burn the fiberglass out, exhaust not loud enough for ya, is that why you wanna do this? :?

I thought it sounded really good, no need to change. Let em get louder over time.

The glass-packs I had on my Chevelle a long while back were just a straight through design with a 4" OD and a 2.5" straight shot through the main body. The 2.5" 'tube' was perforated with scallops that penetrated the 2.5" ID by about an sixteenth of an inch. These scallops were open towards the engine side of the exhaust and directed some of the exhaust flow into the fiberGLASS filling between the ID & OD. Here'* a pic I found online:


You really won't gain anything by hitting the outside of the glass-pack as the sound deadening material is just fiberglass packed between the outer shell and the perforated inner liner. The reason why they get louder over time is because the more you use your car, the more fiberglass gets broken up and blown out the tail pipe until sooner or later, you've got nothing in there to deaden the sound.

Like I said, I had them on my Chevelle. My parents could hear that thing coming from over 5 miles away on a clear day. Once I got a warning for excessive noise, I switched to Thrush Turbo'* and will NEVER go back to glasspacks again. The exhaust note from the turbo'* was amazing and didn't have any of the popping on deceleration like the glasspacks did. There was also enough bass to set off car alarms at my high school when I'd stab the throttle clear the carb before shutting it down!!!

My advice, unless you want your car to be loud and obnoxious, DO NOT get glasspacks.

What'* your opinion on adding a glasspac or turbo muffler in addition to the stock muffler to act as a resonator?

No idea what the result would be. It would probably be more quiet than just the muffler alone, but as a resonator... It probably wouldn't give the desired effect.

Glasspacks are made to be used as a muffler where one doesn't want to wake the dead with straight pipes, but doesn't want to choke off the exhaust flow with a muffler. With all of the performance mufflers available that really don't cut down on the flow all that much, glasspacks are loosing their purpose.

"Turbo mufflers" are generally just straight-through mufflers, if I'm not mistaken.

The Thrush Turbo mufflers that I have on my Chevelle (circa 1994) were just a performance oval shaped muffler with the inlet offset on one end and the exit offset to the opposite side on the other end.

But I will agree that 'turbo' mufflers now do refer to straight through muffler designs.

That makes sense. I had a turbo muffler on my '88 mustang (4 popper) and it set off car alarms it was so loud.