Mechanics

II, 2.9L, 4X4. PUT IN HEADS & GASKET SETS, SET TIMIMG TO PREVIOUS 800RPM. STARTS GOOD BUT AFTER A BRIEF WARM UP LOOSES SPEED OR WON'T PULL & RPM DROPS TO 500. CAN'T FIND THE SPECKS ON VALVE STEM SETTING. WONDER IF THIS COULD BE THE PROBLE

1987 Ford Bronco • 100,000 miles