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.
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.
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.
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.