i have a 2001 Cherokee Sport 4.0 liter. I have already lifted and modified it. Now i am looking for ideas to improve the power of the engine. Any thoughts are appreciated. thanks.

 

Cold air intake (3 inch cone filter and air tube style). 2.5 inch exhaust with high flowing muffler (I used a Flow Master 40). You can put a header on it but, if your Jeep is a 91 or newer the OEM tubular manifold works a s good as any header IMHO. Making a better air pump always increases power. If you have a pre 99 XJ, putting a 99+ intake manifold on gives you about 15-20 more HP. I haven't done this yet but, installing an overbored throttle body really wakes up a 4.0 from what I hear. The ignition is already as good as you'll ever need so, the only other thing I would recommend (and I haven't done this yet) is put a bigger cam in it. I hear Crane make s a good RV type cam for the 4.0.

 

if it is going to be offroad only then get rid of the stock manifold get a header with no cats and you will get a good 10 hp or so

 

you said lifted and modded? what size tires?

 

its got 33" Pro Comp

 

re gear to 4.88 and you wont need to do any other mod you will have plenty of power

 

X 2, re-gear to 4.56 or 4.88, first. You're definitely feeling the poor performance from your Jeep as a result of the 33s with stock axle gears. All the go-fast equipment in the market won't fix that problem, correctly. I have 4.56 gears with 33s, a cold air intake and 2.5 inch exhaust. My XJ has all the power I'll ever need and it still gets 18-20 MPG on the highway.

 

yep... what every one else says... 40 series exhaust kicks a$$, intake is a must if you do exhaust. put an electric fan on instead of belt drivin, yours might already be electric?

 

X100 on the re gearing that is the first thing and then go from there.

 

what axles do you have?

 

What is the smallest size tire you should re gear at?

 

^^^^ X2^^^^

 

Depends But I would re gear for 33"s and I would go straight for 4.88 then you can go up in tire size and not worry about it.

 

yeah when you get in to the 33 range it is time to regear that will bring your performance back up

 

I have the original 91 HP D30 in the front and I have a D44 from an 87 XJ in the rear.