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