I Have had a 1978 F-150 custom for about 10 years now. I has had a 300-6 in it and it finally went out on me. 288,xxx miles on it. Man can ford build an engine. well anyways, I bought another 300 and am rebuilding the motor. I'm just about done, and was wondering how this truck might sound with a glasspack muffler on it. My friend has a 99 Jeep, with a 4cyl. and I thought it sounded sweet. It made me want to put one on my truck. First, can anyone explain to me just how a glasspack works. What are the pros and cons. and what do you think of me putting them on my truck. Thanks allot!

 

I personally don't like a six with a glasspack. They sound like a honda or other foreign car with one of those chrome things they stick on the end of the exhaust pipe. If you want somethng unique, and don't have inspections in your area, get a header with a dual outlet and run duals out the back. You may be able to retro fit a fuel injected six exhaust manifolds on it, since these where dual outlet too. This would make it stand out in a crowd. Glasspacks are basically straight thru and provide very little noise reduction to the exhaust.

 

i had glass packs on my 89 f-150 and my 83 bronco both with the 300 in-line in em. i think it sounded good. not like a v-8 but a heck of a lot better than those japanese peices of crap with coffee cans for exhaust sound. i personaly would go for it. they may smell for a while but that is just the smell of the fiberglass burning out of it for the first couple months. then once it is burned out you will get the true sound of the glass pack.
'75 F-100 4x4, 4" lift
16x38.5x15 super swamper TSL
mini-spooled 9" rear end
390 w/ cam,headers,
and 4 barrell edelbrock

TRIED TRUE and FORD BLUE

 

Glasspacks are JUNK :-X23 get you a flowmaster

 

Is the truck a 4x4 and do you use it for hunting? If so, don't get glass...get a flowmaster.

If you are more interested in performance than sound, get a flowmaster.

If you want the truck to sound like a race car, get the glass.

 

How it works, Packing it with glass.

Glass packs came onto their own in the early 60s. These "Cheery Bombs" have been popular with the hotrod crowd for there deep almost straight through sound, and the police that love writing noise ordinance tickets. Glass packs come in a range of sizes from 1.5" to 3.5" sewer pipes, and in lengths from 18 to 36 inches to fit under almost any car.

There are three basic design used in the manufacture of the standard cigar shaped tube. You can’t tell a book by reading its cover, and you can’t tell what design a glass pack is by looking at the outside. To see how one is made we need to cut one open and peer deep down inside.

Slicing through the outer steel casing (by the way some casings are up to an 1/16th of an inch thick which is why you never hear of an glass pack “rusting out”) the first thing you run into is the packing that gives the (cough, cough) muffler its name. This packing is made from course inlaid 1500* high temperature glass strands, or fiberglass. It’s the coarseness (or air space) in between the fibers of the glass packing that provides the “sound deading” quality of the muffler.

FYI… Did you know that not only glass packs but many aftermarket and factory equipped multi-chambered mufflers also use this high temperature fiberglass because of its sound deading qualities?

Once you get pass the fiberglass you come to the chamber. This is the true business side of the muffler. In the straight threw design of the glass pack there are, generally speaking, three different chamber designs. The first is what is called the louvered designed chamber. Looking down the muffler and seeing pumps rising from the pipe walls identify this style of chamber.

A little note on the physics of sound; Sound travels as a wave, just like the waves in the ocean. The higher pitched the sound is, the tighter (or closer together) the wave peaks are. The deeper the tone the father apart the wave peaks are. The louvered design is meant to trap these higher sound waves, just like you use your hand to trap wind out the window, and dissipate them in the course fiberglass.

The other two chamber designs use holes in the chamber instead of louvers to allow the higher pitched waves into the fiberglass. The only difference beings that one uses thousands of little holes and the other uses wide elongated holes running in sections down the length of the chamber.

I got to clear up one more urban legend-fiberglass cannot burn. What it can do is melt but this is uncommon in glass packed mufflers because of the high heat needed to do this would also burn through the casing. Instead what robs the fiberglass of its sound deading qualities is the impurities (carbon, oil and moisture to name a few) that get trapped in the fiberglass. What does happen is that after long periods of exposure to un-burnt hydrofluorocarbons (dare ya to say that three times fast while drinking a beer) the fiberglass begins to breakdown and is literally blown out the tailpipe.

Ok so there ya have it. The complete where to’s and how for’s of the making design and workings of the famous Glass Pack muffler.

 

If you want a good sound, try splitting the exhaust with headers or a split exhaust manifold and run turbo mufflers. This will give you a nice sound, but not too loud, and will be much less expensive than Flowmasters. Glasspacks are usually too loud after the fiberglass has settled. Turbo mufflers give you good performance and you will still be able to hear your stereo.

 

I have a 1976 F-150 w/a 390 and 32" long glasspacks. It sounds great, even when get on her hard coming off the line. But the only bad part is I gotta crank up my stero to 17 volume just to hear it depending on speed. I love them but wether a glasspack or a Flowmaster sounds better is your choice. I like them both!

 

I had a buddy with a 78 4x4 300 4spd. he put a glasspack on it with 2 1/4 inch tail pipe,,,,It sounded good,,,,and i hate glasspacks. It didn't sound like a foreign junk, And flowmasters are great sounding mufflers, but they sound like ##### on a 300. Go with the glasspacks!

 

Vettelover ---

Wah ha ha ha....I LOVE the 48" thrush mufflers on my 472.....heh heh heh...people KNOW when I womp on this baby and usually back off the pedal if they're trying to beat me to that next red light....

Other than that, they're pleasant to listen to at a stop sign with a 500/500 cam. Georgia State Patrol leaves me alone....but then again they haven't been BEHIND me when I womp on the thing at 65+ mph and I stick my foot into the 780CFM Street Avenger.

 

So, would it be sugguested I get Glasspacks? I've considerd them before but I'm not sure. I'd be using my truck for some 4 Wheeling and driving around on the street. I want a deep throaty sound but not too loud. Cause I wanna still be able to drive at night. Although I do wanna show those ricers I mean business

 

I think it's Clifford that makes the straight 6 headers. I have heard a 300 I6 with headers and dual exhaust, and it was a sweet sounding truck. It was built to about 300 horsepower, and had a type of flowmaster muffler on it. It sounded like a drag racing car, only quiet enough to drive.
I will never again doubt what these motors are capable of; soundwise OR powerwise!
I had an I-6 in my 95 F150. It pulled a car on a dolly for 6 hours at 70 mph IN OVERDRIVE, with no sweat.

Mark
Ford started it; Ford will finish it!

 

No matter how you slice it, a glass pack sounds like a glass pack, and on a 6, well...
On the performance side, stay away from glass packs. A cheap turbo muffler is better, and a good flow master is the best.