I don't know that you "need to have the crank better balanced," since its supported by a main bearing every other throw, although good balance is always important. However, the engine not being assembled well is a possibility. Also could be cam bearings. A Jeep shop that I use told me that a lot of 4.0 low oil pressure issues come down to cam bearing wear and clearances allowing a lot of oil discharge at the cam bearings, and nobody thinks to look for it since its relatively uncommon in other engines. If this was a mass production reman, I betcha they didn't check the cam for straightness before installing it. The last one I put in a v8 needed a few 10-thousandths of truing up before it would spin freely in the bearings. None of this is to say it won't run 300,000 miles just like it sits.
Originally Posted By: Donald
One knowledgeable person told me that in a straight 6 you need to have the crank better balanced than a 4 cyl or V8 due to its physical long length. I am thinking that the engine was just not reman as well as it could/should have been.