The "overlap" is late 1973. Early 73 models have bridged rockers, 74 went back to shaft. There would be a short time when either could be in late 73 models. 64-72 have shaft rockers , 75+ is bridged again. The reason was that Buick sued AMC over the bridged rocker design. Don't know how it was resolved -- whether AMC paid Buick for use of the design or it was thrown out of court as non-patentable or not covered by patent, but it was resolved and AMC went back to the bridged rockers. That last of the 4.0L engines have a stamped steel valve cover. I think 2000-06, but may have been after 2000. Covers don't interchange except over certain range models (87-90, 91-96, 97-99, 00-06... I think) due to differences in the way they bolt to the head. -------------- Date: Fri, 8 Jun 2012 20:28:19 -0400 (EDT) From:adh@xxxxxxxxxxxxxxxxx (Sandwich Maker) if your rockers are shaft mounted - '64-'74 - they're lubed via the gallery and may need the bolt mod. if they're in bridged pairs - '72-up, and yes there's overlap - they're oiled through the pushrods and the bolt mod is irrelevant. afaik no 4.0 heads have tin valve covers. -- Frank Swygert Editor - American Motors Cars Magazine www.amc-mag.com _______________________________________________ AMC-list mailing list AMC-list@xxxxxxxxxxxxxxxxx http://list.amc-list.com/listinfo.cgi/amc-list-amc-list.com