valve-in-head engine (v?lv??n-h?d?)n. An internal-combustion engine, as in some automobiles, that has the inlet and exhaust valves in the cylinder head instead of in the engine block.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.valve-in-head engine n (Automotive Engineering) the US name for overhead-valve engine Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014