The 91-95 4.0 litre HO is by far the best engine ever put in a XJ. The 7120 head casting has the best measured flow of any of the HO heads and it of course had the provision for the temperature guage sending unit in the head. Go ahead and read up on it. You won't get better flow than the 7120 4.0 litre head. I can speak from 6 solid years of beating a 91 XJ with a 4.0 litre HO motor, mercilessly, and it still starts sweltering hot or freezing cold with a simple turn of the key.

 

I'd have to say that 1996 is the best year for the 4.0L.

It seems to be a lot more powerful than any other year 4.0. I've tested my friend's newer XJ, my 92 XJ, and my 96 XJ.

It has an OBDII PCM and 2.5 inch exhaust too. As far as the 97+ 4.0s, they seem to have a higher bias toward fuel efficiency than they do power. The older 4.0L HOs are a little less powerful due to lack of technology at the time.

 

AMC was by far the best American car company. It is a shame that they went under because they were ahead of their time. The inline 6 was/is one of the best engines around, they had crazy ideas like the eagle (30 mpg highway with a I6 car that has 4 wheel drive in the 80s?), and they were reliable. They would crush the competition if they were still around today.

 

Were do you tell what head you have?

 

I have two 1995 XJ's both with the 4.0 ho. My country has 310000 and the sport has 139000. Both start up great and run great too!

 

The casting #s..... not sure where off hand as I haven't had to worry about it. Anyone care to help this guy out?

 

I grew up with 4 AMC's in my family and they were always being worked on (aka broke down). I just dont trust them. I have a buddy who had a 98 XJ and it was a pure lemon. He bought it new and it was one thing after another with it. He thinks Jeeps suck in general now. Is he correct? No, but its his opinion. I know there are a lot of AMC's running high miles on them, but I just dont trust them because of my experience with them. I dont want to be working on my vehicle every other day, let alone when its on the side of the highway. Been there, done that, no thanks.

 

mmmm, remember my first xj. A 1986 pioneer. she was not a limited, no wood sides. but that four cylinder oofaa 2.5 liters. think it had parts from every north american manufacturer. think the electric was motorcraft.. one day on the interstate, she did her best impression of an M-1 abrams laying down smoke when the piston went through the block at the exhaust head. the sound of semi's locking up behind me... priceless.

 

wow....... thanks alot for all the help and input . i have a 92 4L h.o but its getting a bit of a knock but i found a 95 h.o for 500 with a comp cam and new head . em i going the right direction ????

 

At xj101: seems like u are, pretty good price and like i said, my one 95 has 310000 miles on her and she runs good! Leaks alittle oil, but thats no biggie! Good luck man!

 

thanks for all the help just trying to do it right the first time haha , how can u tell if its h.o or not ??

 

This, swap a 99 intake and Neon injectors onto a 96 HO and you have got a mean motor. Never understood why but it sounds much meaner than my friend's 93 with the same mods I have, around 3500rpm it has a real nice roar.

 

yah neon injectors are badass did that swap about a month ago . definate inprovement !!!!!!!!!!!!!

 

but it was in a 92 h.o. . how do u know if its a h.o or not for a 95 motor

 

AMC Jeep's are the main reason why Chrysler bought them in the first place dude.

Then after a few years when they ran out of good parts they started making their designs. AMC is way better than Chrysler period!