whats the best way to get more power out of a 4.0 - JeepForum.com
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post #1 of 34 Old 12-17-2008, 02:38 AM Thread Starter
Goobersbro
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whats the best way to get more power out of a 4.0

okay excluding the throttle body spacer air intake and exhaust what other under 200 dollar mods can i make to increase power out of my 4.0

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post #2 of 34 Old 12-17-2008, 04:26 AM
Richmond88yj
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Good tune up, air filter etc.

And loose weight. Carrying all that extra stuff, hi-lifts, winches, 200lb's of tools, really impact daily driving. Loosing weight is almost the same as adding HP, and it's cheaper.
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post #3 of 34 Old 12-17-2008, 05:38 AM
jeepwrnglr92
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swap the motor out... LOL

mine is a wimp with the 3spd auto. I have tried several things but still wimpy.. Its a Jeep thing

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post #4 of 34 Old 12-17-2008, 06:34 AM
Champion
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put in a crank shaft from a 4.2 (258). it will give you 60 hp. makes it a 4.5L stroker
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post #5 of 34 Old 12-17-2008, 07:09 AM
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Change the cam out for a high performance one. Right around $200 for a Compition cam and lifters.

93 YJ SOA 2" springs front, XJ springs rear w/main leaf added, High pinon 9 inch rear detroit locker front Dana 44 ARB 4.56 Gears, 36 inch Irok tires too much to list. www.mijc.org
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post #6 of 34 Old 12-17-2008, 08:59 AM
jeepster93
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You could try an electric fan.
Easily under $200 in cost.
Will not yield a mess of power, but will give a bit. Perhaps 10-15%(5 to 15 hp).
Also yields some gas saving. Again about 10-15%(1.5 to 3 mpg).
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post #7 of 34 Old 12-17-2008, 10:28 AM
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Quote:
Originally Posted by Champion View Post
put in a crank shaft from a 4.2 (258). it will give you 60 hp. makes it a 4.5L stroker
crank and rods from the 4.2 + the pistons from a 4.0 = 4.5L
Get a bored throttle body from ebay! Bored to 63mm all the way through, Your stock 4.0L throttle body necks down to 55mm http://cgi.ebay.com/ebaymotors/Jeep-...Q5fAccessories


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post #8 of 34 Old 09-27-2009, 12:21 AM
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ttt ttt ttt ttt
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post #9 of 34 Old 09-27-2009, 01:12 AM Thread Starter
Goobersbro
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what the crap this is a post of mine back in my lad days haha
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post #10 of 34 Old 09-27-2009, 10:37 AM
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Quote:
Originally Posted by jeepster93 View Post
You could try an electric fan.
Easily under $200 in cost.
Will not yield a mess of power, but will give a bit. Perhaps 10-15%(5 to 15 hp).
Also yields some gas saving. Again about 10-15%(1.5 to 3 mpg).
Isn't this just a BIT ambitious? What do you all think? Seems like an easy mod HOWEVER, I like the reliability of a clutch fan (plus it sounds good in first gear lol).

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Originally Posted by Goobersbro View Post
what the crap this is a post of mine back in my lad days haha
Yup, newbie here and just excited about making a little more HP and this seems like a good thread. I've done some searches and unfortunately, it seems like the only "no compromise" power increase is a supercharger (of course that requires premium fuel and it does add weight and compromise reliability some due to risk of detonation....so it's not ultimately "no compromise" but seems to be the most desirable alternative barring cost). Also it seems they are too new to get a shot at finding a nice used one ....arghhh. I wish the FIPK was a good mod but it seems too controversial and I doubt you really get the advertised 12 HP increase, not to mention poorer filtration. I do wonder about the cowl intake homemade mod though ...but again, some say the engine doesn't flow enough air itself to take advantage of a better intake design. Here's the catch though, I would imagine a cowl intake really would draw in cooler air ...which makes at least some difference, and the location's pretty good concerning water intake (hell I'm not going to be fording 4ft deep streams anyway).

Arrghh ...so who's done what and how did it work out for you? I want to do something to up the HP but not sure what. Doubt I'd want to do cam because that compromises reliability some and off idle torque. From what they say heads flow pretty well stock and can't be improved very significantly (my rig has 38K miles so I really don't want to pop a valvecover anyway). Barring an aftermarket head that's like 2K LOL yeah right. Rather fab up a homemade SC or turbo kit than do that.

Bottom line, I'd like to somehow see ~210 HP or so with simple bolt on's that won't negatively affect reliability/MPG/etc ....suggestions? Maybe underdrive pulleys and an electric fan, lose the rear seat most of the time and maybe even the spare (for street driving anyway) and see how it feels? I wish the FIPK was a good mod because it's so easy but I don't want to risk getting mud/dirt in the system and it's not worth it for ~5 HP at RPM's I rarely drive at for $250+ ...ok newbie will shut up now but someone please chime in lol.
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post #11 of 34 Old 09-27-2009, 10:37 AM
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Get more power by adding stick-on hood vents from auto zone, everyone swears by them in Va
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post #12 of 34 Old 09-27-2009, 10:41 AM
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Nitrous!

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Originally Posted by mrblaine View Post
I'm a huge fan of body lifts. In fact were I in your shoes, I would have gone for the 4" body lift and some 2" spacers on stock springs.
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post #13 of 34 Old 09-27-2009, 11:03 AM
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One important question is.... Do you want horsepower, or do you want torque? They are not the same.

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post #14 of 34 Old 09-27-2009, 11:21 AM
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Quote:
Originally Posted by tclaremont View Post
One important question is.... Do you want horsepower, or do you want torque? They are not the same.
Actually horsepower is an equation of torque and RPM. LOL didn't you know you were about to open a big can of worms with that statement? Honestly I want BOTH, and that is why an FIPK that would actually deliver as advertised WOULD be nice ...but from what I've read in here (esp the FAQ on cold air intakes) sounds like it's not worth it (unless a homemade cowl setup has been dyno proven to be worthwhile ..doubtful). Many mods increase both, like headers and increased lift rocker arms, cam/head upgrades that aren't too wild (not so high on duration and lift, combustion chamber size, etc). Underdrive pulleys are a compromise to cooling/charging systems at low RPM and don't actually increase HP/TQ but allow more of both to make it to the wheels. Also that's why I say a supercharger is kind of a no compromise solution ....more low end and more top end (esp top end if centrifugal ...which is really what these 4.0's need ...more top end). I assume there is no roots style blower due to clearance issues. lol I'd love to swap my L67 from my Riviera into it (supercharged 3.8).

I know a decent bit about performance mods (have a built/supercharged LT1 Z28) but I'm a newbie to how much the little bolt on's help the 4.0 ...which is really what I'm getting at. So far it looks disappointing, anyone have data otherwise? No fuzzy SOTP data please lol....unless you know of a certain gear you used to take on a hill at a certain speed and now you no longer have to downshift due to a mod or something like that. Thanks, sorry to be so chatty, just trying to be thorough.

I feel like it's probably an issue I should give up on ... unless someone has a nice used SC setup they want to dump for about a grand lol. Probably more efficient to just remove weight from it and call it a day.
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post #15 of 34 Old 09-27-2009, 01:39 PM
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I usually put flames on things I want to go faster.

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