Looking to rebuild my 1993 4.0. I have mechanical knowledge and the book in case it's needed. The book says 4.0's can come from the factory with undersized bores. It then gives the code and a picture of where it should be. Problem is that mine doesn't look like there's and doesn't match the codes. On the flat spot between the coil and distributor it is marked "IIMXII". The M corresponds to an undersized main bearing, the X and I's don't correspond to anything in the book. Any help?

 

What book??? I have rebuilt several engines and all I know of is that on the block mating surface (under head gasket) on most engines is where they stamp the codes. That only happens when the block doesn't fall with in blue print specs and they have to correct it. Undersize mains is same thing only way to check is to pull a main cap off, take the bearing out and look for a stamping like .010 US, STAMPED on the back. If its printed (like ink) its standard size factory, if its stamped SA the engine has been gone through before, and had new bearings installed at some point.

 

Haynes book says between coil and distributor is where it's stamped with codes. Any way to run the build code from the motor to find out?