Merc 454 1995 inboard, 750 hours. No water in<br />engine, just low compression - 120 on several<br />cylinders. Pulled heads had machined. <br />Installed heads new -risers-manifolds-lifters.<br />Installed rocker bolts hand tight- rolled engine<br />until oil was coming out of each rocker. Pulled<br />rocker bolts down to 35 lbs. Valves are non-adjustable. <br /><br />Problem - ran engine for 10 minutes, oil pressure<br />45 lbs. temp 160. engine had a miss. Found cylinders #4 and #6 had 0 compression, all others 145. I loosend 4-6 bolts to hand tight.<br />and had compression. I replaced lifters on 4-6<br />with new, no difference same problem. Have good spark to all, have checked everything 3 times.<br />Watched valve movement, all seem the same. <br />Switched push rods and rockers, same problem. <br /><br />Called machine shop that did heads -- they said to<br />use washers as spacers to extend rocker height ?<br /><br />Any ideas or thoughts welcome - Jerry
