1. #1
    Mudjunky's Avatar
    Mudjunky is offline Junior Member
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    4.0L high output?

    Just wanting to know what was the difference between a regular 4.0 and a high output 4.0?

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    phall92139's Avatar
    phall92139 is offline Senior Member
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    Re: 4.0L high output?

    Quote Originally Posted by Mudjunky View Post
    Just wanting to know what was the difference between a regular 4.0 and a high output 4.0?
    To my understanding the 173 hp, 220 lb.ft., 242 cubic inch 4.0L straight-six introduced by Jeep in 1987 went along pretty well until 1991 when Chrysler redesigned the RENIX engine control computer, intake ports, enlarged the throttle body, redesigned the intake and exhaust manifolds, and added higher output fuel injectors. They also gave it a new camshaft profile. The outcome of all this was an engine that cranked-out 190 hp and 225 lb.ft., earning the designation "4.0L HIGH OUTPUT."
    -Phil

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    Mudjunky's Avatar
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    Ok thanks !! Helps out a lot!!

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    frhrwa's Avatar
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    Re: 4.0L high output?

    seems ashamed they did so much and got so little..

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    Re: 4.0L high output?

    By today's standards, maybe. However, according to an article at Jeep 4.0 liter six cylinder engine, "In 1990, when the 4.0 still had 177 hp, the GM 4.3L V6 only made 160 hp, the Ford 4.9L I6 (used in the F150 and Econoline) only made 145 hp, the Ford 4.0 V6 made 155 hp, the Chrysler 5.2L made 170 hp, the Jeep/AMC 2bbl 360 V8 made 144 hp, and the Nissan 3.0 V6 (used in the Pathfinder) made 153 hp."

    Furthermore, the article goes on to state that "... the Eagle, Concord and Grand Wagoneer, which came with the four-barrel 360 V8, making just 144 hp. The 4.0 I6 made more power than the Ford 302 V8, Chevy 305, Chrysler 318, and AMC 360, as well as any of the 6 cylinder engines the Japanese were putting in their trucks... and it had comparable or better fuel economy."

    Sure, given today's technology I'd love to swap in a Burnsville OffRoad 5.7 or 6.1 Hemi V-8, but our much mis-maligned 4.0's have stood the test of time providing strong performance, great reliability and decent fuel economy (until we start adding on hundreds of pounds of steel and rubber). The biggest problem we have with the modern 4.0 isn't the engine but being locked out of the Powertrain Control Module to affect any real performance enhancements. I think several companies have been successful with various work-arounds and partial "flashes" but for the average offroader, it's an expensive proposition.

    Bottom line...I would much rather have my trusty ol' 4.0 than the V-6 that replaced it. I'll just have to keep on dreaming about those Hemi's.
    Last edited by phall92139; 02-12-2011 at 09:06 AM.
    -Phil

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    superj's Avatar
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    Re: 4.0L high output?

    preach on brother
    I love my old jeep.

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