schardein Posted April 18, 2015 Share Posted April 18, 2015 I have a 1991 Xj with a block casting number of 903MX16. I decode this as a 4.0 built 16 Mar 1989. The jeep is setup as HO, not Renix (which is correct for year). The odd thing is it doesn't have the boss or bolt holes for mounting the ignition coil on the pass side of the block, near the distributor. The coil is held in place by one of the Alternator/AC bracket bolts and looks completely out of place. Everything else looked stock when I got it. Has anyone ever seen this before? I don't have a Renix engine to compare, were the coils mounted differently? Could this possibly be a Renix block in the HO Jeep? I also have a 1991 MJ, engine code is 010MX25 (4.0 25 Oct 1990). It has the coil mounted to the block near the dist like any other 4.0ho I've seen (before the coil pack on the head came out). Link to comment Share on other sites More sharing options...
Megadan Posted April 18, 2015 Share Posted April 18, 2015 My Renix Coil and ICM are mounted to the body on the passenger side of the engine bay directly across from the distributor. Link to comment Share on other sites More sharing options...
Eagle Posted April 18, 2015 Share Posted April 18, 2015 Here's the engine ID info from the 1990 (Renix) Factory Service Manual. This is really the only way to determine when a particular engine was built. The number you posted appears to be the engine build code, NOT the block casting number. Based on that, it appears that you have "decoded" the date correctly, and what you have is indeed an older, Renix engine (or at least block) in an HO vehicle. Link to comment Share on other sites More sharing options...
schardein Posted April 18, 2015 Author Share Posted April 18, 2015 My Renix Coil and ICM are mounted to the body on the passenger side of the engine bay directly across from the distributor. That's what I thought. Eagle, thanks for your reply. Now I wonder if the motor was original to the vehicle or swapped in at some point. It had around 201,000 miles when I got it and was bone stock, although I suspect preventative maintenance had been completely neglected and what corrective maintenance had been done was shoddy at best. Link to comment Share on other sites More sharing options...
Eagle Posted April 19, 2015 Share Posted April 19, 2015 Swapped in. Find the casting number for the head -- see if it matches the block. Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 19, 2015 Share Posted April 19, 2015 Swapped in. Find the casting number for the head -- see if it matches the block. Huh? The block casting number will never match the cylinder head casting number. Head casting numbers are 4-digits, blocks are eight digits. Or do you mean make sure they translate to the same year range? Link to comment Share on other sites More sharing options...
fiatslug87 Posted April 20, 2015 Share Posted April 20, 2015 Just curious, what's in the knock sensor hole? Link to comment Share on other sites More sharing options...
Eagle Posted April 20, 2015 Share Posted April 20, 2015 Swapped in. Find the casting number for the head -- see if it matches the block. Huh? The block casting number will never match the cylinder head casting number. Head casting numbers are 4-digits, blocks are eight digits. Or do you mean make sure they translate to the same year range? Sorry. I meant match for year of manufacture, not that they would be the same number. Link to comment Share on other sites More sharing options...
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