Alright, after viewing a few posts about running an open pipe in place of the muffler i have a few questions.

In recent posts ive read that (Yes, no muffler is bad on the car and then other posts say no its not bad)

Basically 10,000 miles ago my muffler was removed because it was no good. after 7-8 years of wear and tare it had a nasty hole in it some how. so i removed it with the intention of replacing. after a day of driving i just put a straight pipe on to dampen the noise.

alot of you are saying that given the loss of back pressure and low end torque eventually i risk the chance of exhaust valves being burnt up.

Anyone who is considering running an Open pipe. do yourself a favor and dont. you're jeep will suffer getting up to speed and your MPG's will drop. not to mention that if you live in a suburb (which i do not) you'll piss alot of people off.


my question is how long does would you reckon it takes for issues to arise if i were to keep driving like this

if i dont have to replace the muffler asap i won't because its getting to darn cold for it and ive got other projects to tend to such as replacing tires and POSSIBLY diggerizing the jeep before to long (i'll be doing that in a shop with heat and climate control)
Plus the reason i want to diggerize the jeep is because living in the country and doing farm work on the side your car gets dinged up and scratched

if the question i asked has been discussed else where im sorry but i could not really find it.

Dont really know the answer about the valves but the way i see it 50 dollar muffler or few hundered dollar vavles.

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lol

im just asking whether or not it could cause a problem within 10-20k miles.

yes a 50 dollar muffler is cheaper than new valves but ive got enough on my plate as it is. i suppose i could replace the muffler when the jeeps on the lift getting new tires put on :\.

i STILL wanna know the answer though lol

I don't know if anyone could answer that question since nobody has really had to do it. Hopefully one of the resident mechanics can chime in with a few cents worth, but if you're already suffering in MPG's & performance then it may end up costing you more in gas alone.

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Mike D.
2011 Brilliant Black KK Renegade 4x4 (New addition)


2003 Atlantic Blue KJ 2WD

You wont see any real damage from running a straight pipe. The magnaflow and dynomax mufflers used on these jeeps are basically a straight pipe. The only difference is the tiny perforated holes for sound dampening. Now I didnt notice any loss in torque from my straight through muffler(infact my jeep feels stronger), and Im 100% sure it wont damage my engine or yours. Will it sound less tame or bad? Probably. Honestly I would get a nice muffler just to make the vehicle sound better. But then again thats up to you. As for me this is the first vehicle I actually kept a muffler on for an extended period of time in 10+ years and I have had zero engine problems related to it.

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Fran:2002 Jeep Grand Cherokee Limited 4.7 quadra drive. 31in General Grabber AT2, OME HD, bilstein, IRO sway links, addco rear sway. Kolak 3in cat back flowmaster SUV 50, magnaflow 3in cat, airaid JR kit, ram air, P.I.E. aux adapter, surco 45x50, husky liners.http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=6&t=65276&p=719908#p719908

You will have a loss of power and mileage with a straight pipe
another member had his cat go bad, ran it quite a while and when he replaced it mileage went up asnd with it power. The 3.7s need some back pressure to let them run right.
For what a say Thrush Turbo muffler cost( 20-25 bucks ) I am not sure why you would want to wait. The other things are not as important as have a good running KJ!

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MUDD'S MOTORSPORT'S We do IFS lift installs ,
03 OVERLAND EDITION /Kilby-Skidrow-Mopar-4XGuard skids/ 2.5 inch TOTAL CONTROL JBA coilovers -JBA Arms/MOABS-31 FALKEN WILDPEAK AT3W / 4.10's etc, 04 Kilimanjaro Edition loaded, plus 05 KJ limited

Nothing happen to the exhuast valves. Ran open headers on my camro over the summer to my part time job done the street all the time. Only issue was between exhuast pules would suck in outside air and throw off the o2s. Now have 4 inch and runs great. Typical a vehical can pick up around 2mpg. With. Header install so not running a muffler will not hurt anything.

Big difference,and every engine is different and it takes alot of dyno time to actually gain any power or mpg's from headers with the exhuast system you plan on running.Just adding headers does not in any way add more power or mpg's,there is alot more to it.

The 3.7 likes some back pressure.

Oh and just removing just the muffler is not straight piping it as you still have the cats in place.You will loose mpg's and power but with the cats and all the bends before the muffler you should not burn the valves as long as you keep out of the throttle.I would not run it for very long.It takes less then 15mins to replace the muffler on a KJ,regardless if it's cold outside it's not a big job and a $25 muffler will make things all better.

100% agree

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2004 3.7L sport standard 5 speed transmition
ome lift
Dynomax exhaust
k&n cold air intake
Rage roof rack
ultra 16in rims


To come:wheel spacers ,window tint, and off road lights on roof rack, last thing is a arb bumper and wintch
words of wisdom> If she aint 280 she aint a lady haha

I ran open headers on my street/strip 1983 Camaro with an 88-350 in it and never had any problems. Felt like it gained some off the line power. Ran open headers on my 1978 Bronco with a 460....same no problems. Couldn't tell a power diff with it though

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2005 Jeep Liberty.....SOLD =(

1995 Jeep Wrangler YJ





http://www.cardomain.com/ride/3897619/2005-jeep-liberty-sport-sport-utility-4d

Those old school engines respond very different then the 3.7. The powertech series are tuned from the factory at or near their peak (without severly modifying the internals and using forced induction) hence why we don't get huge power gains from power adds. Basically this means any large deviation from the system design and you're looking at a loss instead of a gain. Granted if done right there is a little to be gained, but that's also why you don't see any gasser kjs running larger then 2.5in exhaust.

Sent from my SPH-D700 using Tapatalk

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Fran:2002 Jeep Grand Cherokee Limited 4.7 quadra drive. 31in General Grabber AT2, OME HD, bilstein, IRO sway links, addco rear sway. Kolak 3in cat back flowmaster SUV 50, magnaflow 3in cat, airaid JR kit, ram air, P.I.E. aux adapter, surco 45x50, husky liners.http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=6&t=65276&p=719908#p719908

Generally speaking, the reason exhaust valves are damaged from running without mufflers is that when the motor is shut off, cold air runs up the pipes and cools the valves too quickly. Over time, they get brittle and the head can snap off. However, this is a problem experienced with engines having very short header/exhaust systems.

I used to run a VW drag car. VW headers are really short, even with a stinger... so I just stuck a tennis ball in the end of the stinger to prevent the rush of cold air, allowing the heads to cool slowly.

If you're running stock, cast iron manifolds and a full length system, I doubt you're going to have any problems with the exhaust valves.

If the convertor is still there, you shouldn't have any major problems. My Tahoe has dual exhaust with no mufflers, but retained the cats, it actually runs better being opened up some. The 3.7's though sounds like they need little more back pressure to run good, back pressure helps in the torque dept or low end grunt.... true open exhaust helps with higher rpms with Horsepower

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'99 Tahoe, 3" BL, 285/75/16's , MT II's.
'05 Liberty Sport, -wifey's
'98 Poncho Fireturd, 3.8L, .....the purple pig!