I have a 1991 cherokee 4.0L I6 5speed with a 2.5" lift on 31's, And I have taken it from jeep junker to bad *** trail stomper... but other than a full overhaul I have yet to upgrade the engine.

My question is, what can I do to beef this engine up a little? Im not looking for HUGE performance gains, Its not and will never be a high performance engine. Just seeing what it can get. Im not interested in dropping it and/or tearing it down to the block to do cam's, valves, pistons ect.

Im asking you fine people because I have done allot of research on this subject and always seem to get VERY mixed results.

I Know about the injector swap, and have gone out and pulled eight 0280155703's but am still currently building a DIY fuel injector cleaner.

I know about the 99+ intake swap but have not seen anything that showed hard evidence that it really works.

My thought was injector swap, intake swap, 62mm TB and spacer (as with the intake, have found no evidence it dose anything) along with headers and a 2.5" exhaust system with high flow cat and muffler. maybe performance ignition system later on. If anyone has done the intake swap and/or the 62mm TB+Spacer will you please share your results and any evidence/write ups/reviews you may have?

No... Im not putting a K&N "cold air intake" in it... if this is you, you make me sad. Will be getting a snorkel though...

Compression test.

After all those mods why choke the intake with the snork?

Like said compression test it first that will tell you if your engine is in good shape or has problems.

You forgot full tuneup. fluid change, hoses, belts, etc but that's not what he's asking about.

5 speed on 31s? Throw some axles from a 4.0L auto XJ under there. Very cheap regear from 3.07:1 to 3.55:1. You'll love it.

Also the TB spacer literally doesn't do a ****ing thing. They haven't since carburetors and TBI fell out of favour. Don't waste your money. Intake MIGHT when combined with other mods.

As I said... Have done overhaul. only has 140k on it but did it anyways when i bought it.

All ready did axle swap

Did compression testing when i did overhaul. Good Compression.

All feed back on the spacer has been a resounding NO so... Ill scratch that one off.

I've read about a million threads on more power from the 4.0litre, as far as I can tell the juice isn't worth the squeeze. They never yield the power gains per dollar invested like a V8. I'd swap in a V8 or a 4bt cummins before I tried to hotrod the 4.0l

So you rebuilt the motor and reinstalled the old injectors?

He did a "full overhaul".

yes, I didnt know about the swap at the time. Was focused on restoring it.

I'd steer clear of the snork because they are a choke point on your intake. Do a cowl intake if you don't like CAIs.

What do you need more power for? The 4.0 is a little torque monster. If anything go for something with better gas mileage.

Nice thread

I don't see how a snorkel will be a choke point,It should help its sucking up cooler air vs the hot under hood air.