4.0 vs 4.2

[fubar62172]

What's the main difference between a 4.0 and a 4.2 motor? Do they mount up to the frame the same? Thanks for any info

 

[jps4jeep]

I'd say about .2 cubic inches.

Motor mounts between the two are not identical, but interchangable. the frames between all YJ's (since that is the vehicle that has the 4.2 and 4.0 in the same chassis) are all the same.

Main difference will be that the 4.2 is carbed and the 4.0 is MPI, the only real similarity is the block, and even that is different. The number of interchangable parts between the two is limited.

 

[carnuck]

I pulled the 4.2 from my '84 J10 and bolted in a 4.0L with the mounts from the 4.2L but the intake manifold was too close to the brake booster so I had to swap to Hydroboost brakes. (which is an improvement anyways)