Since its inception in 1968, the Ford 302 was equipped with a pair of one-piece cylinder head gaskets. The gaskets are designed to fill any minute leaks that exist between the top of the engine block and the bottom of the head. If a leak is present, cylinder compression will decline and, in extreme cases, antifreeze will leak into the combustion chamber and exit the tail pipe as white smoke. Aside from disassembling the engine, a blown head gasket can often be detected with a compression gauge.
Start the engine and allow it to idle until warm. Then turn it off.
Remove all eight spark plugs with a spark plug wrench.
Install a compression gauge into any of the eight cylinders. The design of compression gauges varies, but most gauges either screw into the spark plug open or are pressed and held into the spark plug opening.
Crank the engine with the ignition key for several seconds until the needle on the compression gauge reaches its highest point.
Record the reading of the compression gauge.
Repeat the test on the other seven cylinders and record the readings.
Compare the compression readings of all eight cylinders. If the reading of two adjacent cylinders is substantially lower than those of the remaining cylinders, a cylinder head gasket has likely blown.
