00jepxj

i cant find anything bout taking my 4.0 efi stuff and head and putting it on a 4.2 bottom end can it be done and has anyone done it i threw a rod in my jeep yesterday (pics later) i got a 4.2 that runs in my garage i need help

00jepxj

ok so the other day my xj started to tick then by the time i got home it was a knock i checked the fly wheel it was snugg but i like to keep my bolts tight ...so did that ok test drive time start it up allmost no noise go down my road easy on the skinny pedal to hear the noise ok now a right to go around the block take off easy then ...booom! jeep shook and smoked like hell grabed my girl and my atv she drove the jeep whiled i towed it got it home i thinking broke the fly wheel and a cooler line ... next day after work i take the cover of my trans othing wrong then i looked at my oil it was high checked the coolant its gone drained my oil just to see mostly coolant came out ... **** pulled my pan found a bad susprise so i pulled my head and found there was something missing look at the pictures

Outlaw Star

Yes. I ran one. All the 4.0 is a destroked 4.2. The 4.2 had more low end TQ and less high end HP. The 4.0 has less low end TQ (No I am NOT calling it underpowered!) But better top end HP due to the shorter stroke. The 4.0 also has a 1k higher redline. My new motor is a 4.2 bored .030 over to roughly 4.6 liters.

00jepxj

wwill my trans bolt to it and will a 2003 4.0 head work with my coil packs??

Outlaw Star

Yes. But you will have to use the 4.0 flexplate and harmonic balancer and accessory brackets. Dont forget to transfer the knock sensor and such over also. Your best bet on a 4.2 will be from a wrangler.

fishtaconc

No knock sensor 91+

Outlaw Star

Ok. Then he should be fine. I used a 71 IH 4.2 and a 87 4.0 Renix head and accessories.

00jepxj

the 4.2 is like am 80s from a cj we had with a yj body

Outlaw Star

Gotta love AMC, they didn't change much. Even the renix 4.0 was an AMC block.

00jepxj

what year 4.0 head ashould i use i gunna use my coil pack setup but i have the bad 0331 head