How would a person test the compression ratio on a 1969 6.6 liter engine?

Answer 1

If you have the serial number of the car that the engine originally came from, there is usually certain letters or codes which correspond to the motor. Also, if you do a little bit of research you might be able to translate any codes or stampings on the motor itself. This will only be helpful if the motor is still at the original specs and has not been modified or rebuilt with different components that could alter the compression ratio. If you are totally unsure of the history of the particular engine, you can't find any stampings, or if its had any work done to it that could alter the compression, then you almost certainly must dissemble and measure all of the cylinder volume divided by the compression volume at top dead center of the piston travel, this includes combustion chamber volume of the cylinder head. Therefore if one cylinder has a volume of 50 cubic inches and the compression volume is 5 cubic inches, the compression ratio is 10:1, unfortunately this can only be done by really disassembling the engine, so sorry. just to be sure you really don't mean a regular compression test. that can be done with a gauge screwed into the spark plug hole. This regular compression test is done to each cylinder and is most useful to determine if any cylinders have substantially lower compression than rest. This could indicate a problem with the head gasket, valve train or piston rings. The readout from a regular compression test, done at the spark plug hole, is in Psi and can not really be used to determine what the compression "ratio" is.