bigpimpinben said:
mine has the 7120 casting number on it, so it is for sure an ho head?
Yes, it is. Here's the breakdown on AMC242 heads...
#2686 - 1987-1990, "RENIX."
#7120 - 1991-1995, OBD-I HO Head. Noted for raised intake ports (~5/8" inch) and better breathing than RENIX.
#0630 - 1996-1999/2000 (1999ZJ & TJ, 2000XJ) Early OBD-II head. Roughly equivalent to #7120, although the #7120 will edge it out.
#0331 - 1999/2000-current. Later OBD-II head. Can be prone to cracking, and can be readily distinguished by the presence of threaded holes for the coil rail for "distributorless" ignition. May be used on earlier engines.
Note that all AMC242 and 75-later AMC258 heads share a common screw pattern, therefore the heads can interchange. Earlier (say, 75-82 or thereabouts - I'd have to check) AMC258 heads used 7/16" screws, later AMC258 and all AMC242 heads used 1/2" screws.
If you swap your cylinder head for another from a different year, use the head gasket
for the head you're using. Note that Fel-Pro P/N 9076PT-1 will work for 1987-2001 AMC242 - probably later, but I haven't checked (this from the label on the head gasket package - I happen to have one that I was measuring to make a torque plate...)
5-90