[txasylum]

I just bought a 89 jeep cherokee. The guy I bougth it from said he replaced the motor with a high output 4.0. He gave me 5 of the 6 injectors for the motor, but since it was missing the 6th injector, he put the standard 4.0 injectors on the motor. My question is how do I know if I actually have the high output motor? If I do, I will purchase a new injector and change them out. Or does it really matter on the injectors?

 

[LJameson]

There's more to the High Output then just the block and injectors. It's also exhaust, completely different EFI system, and a different intake. I don't see someone going through the work of swapping in a different system for a 13 hp gain.

 

[peeweeXJ]

If the motor is actually a 4.0H.O. you do not want to run RENIX 4.0 injectors on it. You might be ok because the H.O. fuel demand may not be much more than the RENIX. The spray pattern could be different though.

I believe the Renix 4.0 throttle body is held on with three bolts in a triangular pattern.
The H.O. 4.0 uses a bolt at each corner. You could possibly tell the difference by that.

 

[txasylum]

But how do I determine if I have a High Output versus a standard 4.0? What do I look for on the motor to determine the difference?

 

[Happy Joe]

The most obvious difference, I believe, are that the HO version does not have the knock sensor and does have the 60mm throttle body.
Not certain about the early HOs but the later ones had sequential as opposed to bank fire injection.
The better HO heads have the raised ports.
The best HO intake manifold has the curved runners, but earlier HOs had the same shaped intake as the non HO engines.
I would wager that the HO came with better fuel maps in the computer and a different cam.
The casting number of the non-HO 4.0 head is 2686
The casting numbers of the HO heads are (Edit; changged 7021 to) 7120 (typo ... sorry!) (desirable), 0630 and 0331.

This thread may help;
http://www.jeepforum.com/forum/showthread.php?t=623591

Enjoy!

 

[txasylum]

I just looked at the casting number on the head and it is stamped 7120 and there is another L23 on it. Is this the HO motor?

Also, I looked at the injector rail that I have in the back of the jeep and it mounts differently on the motor than what is on there. the holes for the bolts on the rail is different. The injectors on the spare rail is marked 332 something.

 

[txasylum]

I got it figured out, but there is a still a problem

Okay, I figured out I have a 91-93 HO 4.0. But , the manifold, throttle body, and injectors are from a standard 4.0. If I want to convert this over so I can take advantage of the high output, what all do I need?

 

[Happy Joe]

Yes , 7120 is correct (sorry about that).
If you have room change to the newer curved intake and injectors & throttle body the biggest improvement will come from the larger throttle body. (I'm not certain if the larger throttle body TPS is plug compatible with your harness; suggest some investigation).

Enjoy!

 

[FairlanePhil]

delete

 

[1986cj]

91-95 are HO 4.0s 96 and newer are obd2 and not the same. Non HO? You mean earler XJs 4.0? they are all renix systems in tell 91. I have never heard of a 91-95 non HO 4.0 but I have been wrong before.