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Hi, if you only have 40-60 psi compression the problem will typically be jumped cam timing and bent valves. A cylinder leakage test is better than a compression test to check for the problem. A leakage test pressurizes each cylinder while at TDC of it's firing stroke so you can check to see where the air is escaping. If the air is coming out of the exhaust pipe you have bent exhaust valves. If the air is coming out of the throttle body you have bent intake valves. If the air is coming out of the oil filler cap you have a piston ring problem.
A head gasket will show up in the coolant tank with air bubbles when you pressurize the cylinders.