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Old 11-07-2012, 07:30 AM
cdminter59 cdminter59 is offline
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305 compression testing

Most 305 heads have a 58cc chamber or smaller and small valves. The larger valves help with higher RPM flow. The 350 truck heads have 76cc chambers with valves as small as 1.72 & 1.5 to 1.94 & 1.5. Here is some examples. An 305 engine with 5cc flat top pistons and 58cc chamber heads will have a compression ratio of 10.0 while the same engine with 76cc chamber heads will have a 8.2 compression ratio. Another 305 engine with D cup 12cc pistons with 58cc heads will have a 9.2 compression ratio and with 76cc heads will have 7.7 compression ratio. As for testing compression on each cylinder by turning it over by hand IDK, but logically thinking I would not think you could spin the motor over fast enough to get an average reading.
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