{TAIL ~ Means} are provided for adjusting the relative timing of {HEAD ~ the two pistons} so as to vary the compression ratio of the engine 
{ TAIL ~ Means } are provided for adjusting the relative timing of { HEAD ~ the two pistons } so as to vary the compression ratio of the engine
TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH