zwanboy104

Has anyone ever put a glasspack muffler in place of a cat converter before? I have a flowmaster exhaust, but just hate the cat it has. It eliminates so much of the sound the car has. How would it sound having glasspack in place of it? would it make it any louder?

//<86TA>\\

iTrader: (14)

a new high flow cat will keep you legal, and eliminate the original, probably shot/plugged stock cat.

sam24th

iTrader: (1)

2x on the new high flow cat. Mines shot to hell right now so ill be swaping it out sometime this week after the engine is back in it.

remltr

iTrader: (4)

If you're worried about sound, just replace the cat with a straight piece of pipe?

norcalz28

iTrader: (13)

I used a carsound (magnaflow) cat to replace my not that old catco cat, and noticed a much better sound.

UnderCover89TBI

iTrader: (25)

Yes im a fan of the Carsound converterers too...for aftermarkets....other than that if you dont mind risking a fine you can run no converter and get all of that engines sound

Matt1821

What about back pressure? Eliminating the converter and replacing it with straight pipe you will lose significant back pressure and more than likely some power as well.

UnderCover89TBI

iTrader: (25)

oh god...not this again. you DO NOT want backpressure. you want velocity.

luvmy64

I actually did replace the cat with a glass pack on an 89 i had, and it had a flowmaster muffler. It made it A LOT QUIETER. If you want louder, go with a straight pipe.

///DAN///

iTrader: (1)

I went with the straight pipe . Living in Pa as well you will not get fined there is no one looking to bust ya , now living in California where from what i understand they have emissions check stops i wouldn't do it. I talked to my mechanic he said keep it under 5000 miles and he doesn't care talked to the owner of the exhaust shop that made my pipe and he said the person who gets in trouble is if a shop were to install the pipe , he followed that up with don't bring your car here I won't work on it like that.

UnderCover89TBI

iTrader: (25)

Yeah I could see California fining shops for not reporting a known problem with a car. Bad enough we "have" to check the tire pressure and adjust if out of specs.

50shadesofplum

previous owner of my 97 tahoe replaced the cats with glass packs, and it runs horribly due to lacking o2 sensors, and back pressure. It sounds horrible and backfires like a shotgun at highway speeds. Also went from 13/17mpg to 8/10mpg. Absolute garbage idea in my opinion.

norcalz28

iTrader: (13)

I have a car sound converter on mine, and I sometimes replace it with a Mac off-road pipe. You only really notice a sound difference at WOT. The car sound does very little to muffle the sound. I'd go that route before you put a glass pack there. I've heard LT1s with cats and GMMG, and it was loud. You can get a good highflow cat to keep the back pressure up.

Griffin92rs

I just put a pipe in place, sounds great too. And didnt effect mpg at all. my low mpg is due to my in town driving... driving good tho its 19/25 city/hw.

jay123

Im running a glasspack where the cat is usually located.. Take the cat off, throw it in the woods, put the glasspack in its place and then straight pipe the rest of the way. I have the same setup on my car and it sounds awesome!

83 Crossfire TA

iTrader: (2)

1- back pressure does nothing to make a car run better. You want as little back pressure as possible. Period. For the 2 or 3 of you that have said something like that in this thread QUIT REPEATING THAT STUPID ****!
2- modern cats don't produce significant back pressure at reasonable flows. Your typical modern (anything monolith based after the mid/early 80's) 3" cat will outflow most 3" performance mufflers.
3- cats deaden noise less than a glasspack, installing a glasspack will make a car quieter. A many glasspacks are also a bigger flow restriction than cats (it depends how the tube perforations are made and the core size- many glasspacks use louvered cores that are pretty restrictive and it's not uncommon for the core to neck down vs the inlet/outlet)
4- I haven't looked in a carsound box lately but unless they changed something they are just repackaged chevy truck cats. So are magnaflow. Dynomax are just Walker stock replacement cats...

jay123

Back pressure really only comes into play with older carbed engines. Here in Canada, if you were to run straight pipes off of headers then the exhaust would not be able to retain enough heat to keep the gas from freezing as it enters the carb.

A glass pack will make the car quieter, but just enough that you don't get the cheesy crackle and backfire from a completely straight piped system. The perforations are there for a reason, they are designed this way to allow you to install it in what I call either Loud, or really loud format.. Says so right on the box. I am yet to see one that was smaller inside on one end than the other.

-------------air-------->>> //// baffle//// = Louder

------------ air--------->>> \\\\baffle\\\\ = quieter.\\


If you can leave the converter and mount the glasspack down the line from it that would be best as you will reduce your admissions and if you get rid of it you will notice a big increase on exhaust smell.

VTSummit

I have a flowmaster exhaust from the manifolds back. Originally had a test pip in place of the cat- so 3" w/mandrel bends the whole way back. Sounded mean, lots of burble on decel and sounded really obnoxious (in a good way) at full throttle.
Have to get it compliant again, so installed a Magnaflow high flow stainless cat. Killed a lot of the noise that I loved about the car. It's nowhere near as nasty sounding. I'm a law and order kinda guy, so I'm not going to run with an illegal setup- but I miss the sound.

redneckjoe

can always take the cat out and gut it, then re-install it so the smog police can see it in place. a long pipe and hammer work good to knock the honeycomb internals out.

for glasspacks i really like the summit house brand. they have a directional, spiral, louvered, center section. nice quality. theres a video showing the inside of them in the link; https://www.summitracing.com/parts/sum-630820/overview/

Camaro-3

I hesitates too between a glasspack and a cat but not for the same reasons... The last owner installée a performance exhaust system on a shell i bought, but i installed a stock 305 in it. The car have short headers, with 2.25 duals, then 3 inch single to the muffler (probably a flow master), without a cat.

The engine sounds not so bad, but too loud and i dont want a ticket or wake up neighbours. I prefer not replacing the exhaust system, since its a Nice improvement in performance for a stock engine. But i really want to have like 5-10 décibels less if possible.

with a low budget, i hesitates between 3 choices (i keep the performance muffler and headers) :
-install the stock catalytic converter i have in the shelf
-install a 70$ new universal catalytic converter from summit
-install a long glasspack (no cat) and weld the 2 sides of an empty cat to this glasspack.

i have no emissions tests to pass. Which choice would be the quietest (at idle and part throttle) without losing too much power or gas mileage from now? Any advices on a particular type of cat or glasspack?

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redneckjoe

if your just looking to quiet the exhaust down, you can make or buy some exhaust baffle inserts. the good thing is, you pull them back out anytime you want it louder again.

83 Crossfire TA

iTrader: (2)

That makes absolutely no sense. The freezing temp of gasoline (depending on blend) is somewhere between -50 and -97*F. I don't believe that anyplace in North America gets that cold regularly (Alberta's travel site says "They can drop as low as -30 to -40°C (-22 to -40°F) for short periods of time."). Even if that wasn't a problem what do exhaust temps have to do with gas freezing? You mention headers so I'm assuming that you're not talking about a stock manifold type heat stove. Even with all that, if you're talking about using a modified muscle car on the coldest winter night... well that seems more than a bit crazy.

Even then backpressure does nothing good for an engine. If you want it to maintain exhaust heat for some reason then don't put headers on it or if you do coat/wrap them.

83 Crossfire TA

iTrader: (2)

If it's a flowmaster muffler cut that off and replace it with something like a dynomax ultraflow welded (offset offset deadens noise more, offset center or center center flows more) and it will sound just slightly louder than stock and flow more than the flowmaster or with something like a dynomax super turbo and it will sound pretty close to stock and still probably flow more than the flowmaster, or even a stock 4th gen muffler will be much quieter (4th gens were quieter stock than 3rd gens) and still flow more than a flowmaster. Typically the bigger muffler case the more it will deaden sound and the more it will flow compared to a similar smaller cased muffler.

Of your choices, either a stock or aftermarket converter in good shape will deaden some sound and flow more than most glasspacks.