Okay, finally decided to pick up my1972 240z from the mechanic. Charged me US$160 for changing the fan clutch, thermostat, wrapping heat shield cloth on the fuel lines and replacing wáter pump. He also changed the exhaust manifold pipe gasket. Car timing was set at 10BTDC. Car ran fine. No backfire either from intake or exhaust. However, once i reached home while playing with the car stereo temperature started to rise until reached 3/4. RPM dropped from 1000 to 500 and then raised to 1000