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Wednesday, October 31, 2012

Are glasspacks even legal?

i live in oklahoma where we do NOT have emissions law. since we dont have the law would i be legal to do exhaust work and putting a glasspack on my s10? are glasspacks even legal to use due to the sound? if not what muffler would you recommend for a 6 cylinder engine for a good deep rumbling sound?


  1. You might check with your motor vehicle department or bearo of automotive repair. Here in California we have the toughest smog laws going. As far as glass packs are concerned, here the maximun noise level is 95 dB and I had glass packs on my 1977 Suburban (with crossover pipe to mellow it down a bit). BTW, any vehicle 1975 and older are exempt from smog regulations. I want to put a true exhaust system on my 1995 GMC K2500 Suburban and the law forbids this. As it came with one catalytic [pellet] converter I cannot have two cats installed - sucks bigtime...

  2. I love glasspacks.

    Most people turn their nose up at them and recommend Flowmasters instead.

    You can hear comparisons on Youtube. But the problem with most of the videos I've seen on there is they either compare on different vehicles, or admittedly don't mic the two the same so one gets trumped by the other without things really being even.

  3. if not what muffler would you recommend for a 6 cylinder engine for a good deep rumbling sound?

    Split the manifold and put dual straights on it.

  4. I've been considering putting one of those exhaust cutouts going through a glasspack on my truck, for use on country roads.

  5. I always go for the lowest amount of noise possible myself (and it may make it easier to sell later on), but if you like the loud sound of glasspacks and your state doesn't have emission laws, you could just cut the catalytic converter out and add a glasspack. You may need to do some customizing by cutting some pipe and using some adapters, but you should be able to do it. Check the noise laws, though. You may have problems with that.

    If you want a rough measurement of noise level and have an Android phone or tablet PC, buy the "Smart Tools" application. It has several useful tools, and one of them is a sound level meter that reads in decibels. It doesn't have the advanced settings of a real decibel sound level meter, like A-weighting and such, but it will get you in the ballpark. I would take a reading about 25 feet away.

    Keep in mind that you may be violating federal emissions laws when you do this. But I haven't seen any federal enforcers checking automobiles for proper emissions equipment. :-)

    If you do the swap, or even just add a low restriction muffler in place of what you have now, try to keep the oxygen sensors in about the same place as they are now. Those feed back to the engine control module to make adjustments in fuel mixture.

    Someone else here who has done modifications to their exhaust system may know more about what you can get away with as far as the oxygen sensors go. You may be able to substitute something like a resistor to give a false reading of the exhaust. .

    While you're at it, consider installing a K&N filter in your air intake system. Or, if you have the money, consider a low restriction intake system. You can find some DIY instructions and videos for the S-10 on how to do this, or you can buy a prepackaged system that will install in a short period of time. I think these cost around $200 and get you about a 10% increase in horsepower for a 4-cylinder S-10 (that's what I have). It should give you a decent improvement on the 6 cylinder version also.

  6. oklahoma doesnt have emissions law. i called autozone they said check with city for ordinance for sounds. city says im out of city limits which i am by 4 miles and they call sheriff to check. sheriff says its state. state says modifying exhaust muffler or anything is illegal but they wont pull you over for it.

    also this is first one ive ever done. is the longer or shorter glasspack loud? i want something midways. whats shortest size? 12 or 16 inches i think and 30 is longest.

  7. Excellent post. Please keep up the great work.