In a preferred example, {HEAD ~ the engine} has {TAIL ~ a spark plug access} well centrally located at the top of each cylinder 
In a preferred example , { HEAD ~ the engine } has { TAIL ~ a spark plug access } well centrally located at the top of each cylinder
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH