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Unread 01-16-2005, 01:24 PM   #1
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Join Date: Dec 2004
Location: Westminster, CO
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Want more power for 4.0

I have an '04 TJ with the 4.0 liter six and want to know what really works - defined as measurable power increase. For example, Airaid advertises 11 hp and 14 lb-ft of torque when added to a stock motor. Is this real? What are the best HP for the dollar adds. And which ones are a waste of $$$?

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Unread 01-16-2005, 01:35 PM   #2
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2005 LJ Wrangler 
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Location: Ellicott City MD
Posts: 2,218
some people say intakes work, some say they dont. id say if you want real power go with avenger supercharger or gears
2005 Unlimited Rubicon Hard N Soft Tops, Clayton Long Arm on RE Coils, Warn Bumper/Tire Carrier, Warn Winch N Bumper, Currie Steering, JKS Quicker Disconnects, JKS Front Trac Bar, Bilsteins, CO2 System..Yada Yada Yada
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Unread 01-17-2005, 01:56 AM   #3
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1988 MJ Comanche 
Join Date: Jan 2005
Location: Southeast Kansas
Posts: 13
I'm a big beleiver of in-line sixes. And definatley believe in the 4.0!!!!!
Depending on the amount of money you would like to invest is the main factor.
Let's just get down to it . Talking with Clifford performance in Califonia and a little bit of drag racing background I built a 230+ hp 4.0 to put into an 88 Jeep Comanche 4X4 2 years ago. nothing compared to the 350+hp motor that Clifford offers, but then again I couldn't afford the $5000.00 plus shipping price tag.
I had a set budget of $2000.00 and alot of time.
I had the block bored .060 over because of the wear on the number one cyl..
The crank was turned and polished and new bearings were installed, new pistons and chrome molly rings.
A high volume oil pump was installed along with a 240 degree mild off-road racing cam (wasn't suppose to be street legal, but who's gonna know).
Had the exhaust ported and polished and the intake just ported(no polishing done here).
Don't know the part numbers off the top of my head, but i installed oversize fuel injectors to provide 10% more fuel feed along with a little lap-top plug in manipulation.
Created and installed a cold air intake using a K&N 13 inch cone air filter.
then added a cat back dual exhaust.
I'm not sure if this is exactly what you might be after, but if you are i know that i still have alot of info packed up in the garage in the filing cabinet with exactly everything i did to this motor.
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Unread 01-17-2005, 06:48 AM   #4
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Check out this website:
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Unread 01-17-2005, 01:27 PM   #5
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1991 XJ Cherokee 
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Location: Denver, CO
Posts: 1,184
I just put on a cold air intake, 58mm throttle body and a 3/4 inch spacer, and pacesetter headers. I've almost got the money to finish it with a high flow cat and a cat back system. But even without those two components it's got a tremendous amount of power compared to stock. It's no porsche but for something so big it accelerates very quickly. It's got enough umph that if I'm not careful on the gas if I tap it a little in a turn the torque spins me out. I highly recomend starting this route. An intake Tb and spacer, new headers and a cat and exhaust all togethor is less than $1000 if you shop around and wait for a deal. I got all of my stuff on ebay.
"Nitrous? So is that like viagra for your Jeep?" -mom

"I flopped it"
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Unread 01-23-2005, 08:57 AM   #6
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Air intakes most likely will NOT gain you what the manufacturer claims. If Jeep didn't put an electric fan on the 04' Wranglers, replace the water pump-mounted fan with an electric one. This will gain you a good 4 hp over stock, and that's from idle to redline!

A ported/polished cylinder head is an excellent mod and isn't too difficult to perform yourself. I would recommend using a head from a 91-95 4.0(casting 7120). They flow better than all other 4.0 heads and would require removing less material. Here's a link for more information:ported 4.0 head

Also, going with an aftermarket camshaft would help bring out more power from that ported head

If you want to go wild, go with a stroker moter. Best bang for the buck mod you could do to the 4.0
99 XJ Cherokee, 2 door, 4.6L Stroker, 5 speed, 4x4, 8.25" rear, 3.07 gears
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Unread 01-23-2005, 10:48 PM   #7
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Thanks for the porting link.
Saved to favorites.
Out of the darkness comes light.
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