kyleag89 Posted June 18, 2009 Share Posted June 18, 2009 Well hello everyone. I just purchased an 89 Comanche for my next project. It has the I6 with the auto tranny. My father is a member on this site and he also has an 89 Comanche that we restored together. My question is... will the motor loose most of its power due to running an open header? I drove it into work today so I could replace the brake lines on the lift and it had no power. Right now the pipe is broken clean off at the cat and I'm hoping that is why there was no power. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 18, 2009 Share Posted June 18, 2009 While the I6 needs some exhaust back pressure to run at it's peak, it should run okay (read not sick) if the engine is healthy. When I had my dual exhaust put on I ran it to the muffler shop about two miles away with nothing but the header and a short exhaust pipe. Ran fine; LOUD as he!!, but no real noticible loss of power. Link to comment Share on other sites More sharing options...
jpdocdave Posted June 18, 2009 Share Posted June 18, 2009 probably has 3.07 gears to, terrible gearing. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 18, 2009 Share Posted June 18, 2009 Most likely 3.55 w. the AW4. :D Link to comment Share on other sites More sharing options...
DirtyComanche Posted June 18, 2009 Share Posted June 18, 2009 It probably has other issues. I drove mine with an open header for a long time. The 'power loss' is over-played. The stock header even has an awesome built in restriction to help keep some back pressure anyways. Link to comment Share on other sites More sharing options...
jpdocdave Posted June 18, 2009 Share Posted June 18, 2009 Most likely 3.55 w. the AW4. :D Â my aw4, and most that i have talked to are 3.07 Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 18, 2009 Share Posted June 18, 2009 I've had three XJs and one MJ w. the AW4 and all had 3.55 gears. Just shows (again!) nothing is written in stone with these things. :D Link to comment Share on other sites More sharing options...
BJA814 Posted June 18, 2009 Share Posted June 18, 2009 AW4 and 3.55's here  And open exhaust is loud...an annoying kind of loud, but shouldn't affect power to the point where it's noticable. Link to comment Share on other sites More sharing options...
DirtyComanche Posted June 18, 2009 Share Posted June 18, 2009 Most likely 3.55 w. the AW4. :D Â my aw4, and most that i have talked to are 3.07 Â Â Â Highly doubt. If it is, I want a picture of the tags and proof that it was orig, as it does change things (for me). Â 4.0 5-speed should be 3.07 4.0 and automatic should be 3.55 Link to comment Share on other sites More sharing options...
dasbulliwagen Posted June 18, 2009 Share Posted June 18, 2009 Is the exhaust broke off before the cat or after the cat? If after, then you may want to check and see if the cat is plugged up. If it broke before the cat... well your guess is as good as mine. Just my 2 cents. Link to comment Share on other sites More sharing options...
kyleag89 Posted June 18, 2009 Author Share Posted June 18, 2009 My jeep has 3.55 gears... I am eliminating the cat because I don't need to have one in MA anymore. I am keeping it simple and just putting a strait pipe in to connect the header pipe to the muffler. Link to comment Share on other sites More sharing options...
ratrapp Posted June 18, 2009 Share Posted June 18, 2009 my 88 4.0 aw4 has 3.55s as well. Link to comment Share on other sites More sharing options...
OSHAGNASTY Posted June 18, 2009 Share Posted June 18, 2009 before i got my exhaust welded back on i had power but u had to give it extra than normal. Link to comment Share on other sites More sharing options...
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