is there any difference between the 3.9L and 4.0L cylinder heads? Are they interchangeable with each other? And would it be worth puttin a 3.9L head on a 4.0L bottom end if the 3.9L head has been ported and polished?
Any help will b appreciated
Cheers Bazzo

they are virtually the same, and are interchangable.
there are a few small differences, but nothing to write home about

EA's have smaller chambers because of the swirl ridge, so putting an EA head on an EB will raise the compression and putting an EB head on an EA will drop the compression.