What is the best power adders you guys(and girls) have added to your 4.0 engines , and do you think it was worth the money you paid. Thanks for replaying in advance!

super charge it  

AEM Brute Force intake.  

Why not the K&N system? It is quite pricey if you ask me......  

my jeep guy told me to go with the Brute Force.  he pointed out that it uses an aluminum tube and heat shield versus k&n's plastic shtuff, similar washable hi flow filters, and lower price.  performance numbers i've read in magazine tests also show the AEM producing slightly better numbers.  neither will produce dramatic results but, you will notice a throatier sound upon acceleration and slightly better torque range.  i initially was drawn to k&n's name, but i feel i made the right choice and am very happy with the AEM.

What about thoughs drop in ones that replace the factory airbox and use the factory air duct coming from the outside of the engine compartment for a cooler charge. They aren't really all that cheap though........Anyone have a Header on their 4.0? are you happy with it?  

my '97 came from the factory with a header.  all 4.0 TJ's did.

not sure about  the cherokee, but the TJ header had a problem.  will crack.  had mine fixed while it was on the jeep.  they got 98% of it.

my 2 cents.

Pete

Depending if you have carb or fuel injection, a manifold offhausen makes to accept a 4 BB carb is fantastic!

Or a new air intake for your throttle body is great also

these are the best I know, at least the most substantial in gains

mine is a fuelie, 96.  

I have read you can get allum head for them now.  

I wouldn't suggest any high performance air intake. It kills your engine twice as fast. You'll see lot's of old muscle cars with the high per air intake shut off their engines if they come to a stop light for long enough. That's why. Air intake just thins out the gas and makes the engine feel like it needs to work harder. In the long run...only get them if you have the money to pay for more repairs. I wanted to put a bigger throat on my 77 Camaro by cutting the throat shorter which would take more air in, but my dad warned me not to. If you want a couple more HP, add a new high performance ingnition system.  

Are you s hitting me?  I love a sense of humor, but not when a guy asks for legitimate advise.

The reason "old-school" hot rodders shut their engines down instead of subjecting them to prolonged idle times was more due to marginal/inadequate cooling systems (stock cooling systems for modified engines, no "uncool" fan shroud...).  Why were the cooling systems inadequate?  Mostly due to the increased HP without increased cooling capacity.  Perhaps, as well, the numbskulls didn't re-jet their carbs to compensate for the open-element (hi-flow) air filters.  this caused a lean condition, which introduces a host of other ails.  In a 4.0, which is injected, the PCM ajdusts the stoiciometric fuel ratio (roughly 17:1) several times/second.  Changing the airflow charicteristics by way of increased efficiency of the air cleaner would be compensated constantly - it would NOT lean-out and cause troubles as it would on a carbureted engine.  As long as the filter adequately prevents airborne particulates from entering the intake, you are better off with lesser restriction. period.

Well said OHJPR.  IMHO, the only time you would need to worry is if you forced air into it via turbo/supercharger.  Then you probably need to reprogram the engine management system.  

I have a highflow filter, cat and exhaust.  My TJ runs great, get's better mileage ...

I used to drive a FSJ, with a worked  360. Headers, open 3 1\2 inch oopen exst, and nice cam. had a new intake manifold but ran out of money to get a card. but now I down sized and got a 5speed XJ. I cant wait to istall a new intake and exst. in my opion thats the best way to gain  power. think about it like  aafter eating a big   meal, you feel good for a little while but to feel real good you got to get rid of it all.  

Wow this is turning into an interesting thread....... also on the muscle car thing , somtimes they cannot sit running because the cams are so big and they have a loss of vacum.........And ya I did see that you can buy a alm head for the 4.0's now........if I only could aford it LOLOL