89 yj 4.2 swap from 94 4.0 yj

[harvsyj]

hey fellow jeepers, ive got a very solid 89 yj with a 4.2 and 5 speed trans, after researching my options i found out that the pukejunk trans and transfer case is not worth leaving in the jeep cuz its car trans, so i found a completely rusted to nothing 94 yj 4.0 x15 trans in good running condition, im planning on swapping all trans, transfer case wiring, computers, fuel injection, gas tank etc, the 4.2 engine in the jeep has 107k and ran good before i tore it down, ive seen 1 post where the head and intake was installed on the 4.2 block, a lot of work, my question is will the intake from the 4.0 fit the 4.2 head thus not having to break the motor down any further, thanks any help would be great

[Cheromaniac]

The 4.0L intake manifold will need some "massaging" to make the runners line up with the 4.2L head's intake ports. Since the 4.0L head flows so much better than the 4.2L head, and has a smaller closed chamber that raises the CR (more power), I suggest you swap a 4.0L head as well as a 4.0L intake manifold onto the 4.2L block.
With the OBD1 ECU, ignition, & fuel system from the '94 YJ running the show, a 4.0L headed 4.2L engine will kick some ass.