Getting the most out of my 258?

[notarubicon]

So I have an 84 CJ7 and I am trying to find ways to get the most out of the motor. It is bolted to aT5 Transmission and a twin stocked Dana 300 . So what can I do to squeeze some more power out of it?


Sent by carrier pigeon

 

[Torxhead]

One of the most inexpensive ways to get a little more out of the AMC 258 i6 / 4.2l , would be to modify the distributor using the "Team Rush Upgrade", which is installing a larger distributor cap, different rotor, and ignition wires. It is listed in this forum. The later CJs had quite tall differential gearing for what I would guess to be for lower emissions purpose. There are fuel injection kits available for that engine, but can get expensive, most guys are happy with changing carbs. The later 258s come with a lot of vacumn hoses, and when they leak can have an effect on performance. I would also suggest following Jeep forums like this one.

 

[PaRenegade]

Since it's an 84 you should have the underdash computer. So another common mod. to the last few years of the Jeep (83-86) was the "nutter bypass". Do a search theres a gazillian threads on it out there. Here's one:
How to - Nutter Bypass - JeepForum.com

You didn't say what gear ratio you have in your jeep now. That's also an alternative to getting more power. If you got high gears like 2.73's you could change those, but that's a more expensive direction.

 

[gert]

4.0 head swap mill the head to bring compression up and a MC2100 carb or GM TBI after your Nutter Bypass and Team Rush , then swap to some lower gears last
Jeep Strokers • 4.0 head and EFI on a 4.2 block
The Junkyard TBI write-up - JeepForum.com
http://www.jeep-cj.com/forums/f2/motorcraft-2100-replacement-12181/

 

[Sasquach]

I put a 4.0 head and stock 4.0 tubular header, recommended crane cam for fuel injection and the mopar fuel injection on my AMC 258 i6 / 4.2l and runs about 100% percent better than stock.
Not the cheapest but if it's in your budget you will be pleased.

 

[ThisGuyUKnow]

4.0 head swap mill the head to bring compression up and a MC2100 carb or GM TBI after your Nutter Bypass and Team Rush , then swap to some lower gears last
Jeep Strokers • 4.0 head and EFI on a 4.2 block
The Junkyard TBI write-up - JeepForum.com
http://www.jeep-cj.com/forums/f2/motorcraft-2100-replacement-12181/

The 4.0 head and MPFI

Maybe a regear depending on the size of your tires to keep that T-5 from blowing up.