Curiosity. Knowledge. Power.

ENGINES DAY ONE

A simple four-stroke engine can be thought of into three separate main parts: The head, block and sump.  The head sits in the block while the sump is bolted underneath.  

The process of the engine can be thought of into four main actions: intake, compression, combustion (stroke), exhaust.  Each step is vital and everything depends on a "cambelt" or "timing belt" which runs the cam pulley and the crank pulley.  Note that these pulleys sometimes are held together by a chain or "cam chain".

Rob explained that the exhaust valves are actually smaller in diameter than the intake valves.  This is because the intake valves need to open a larger pathway for a fuel and air mixture.  This was important to know to keep parts organized.

DISSECTION

Dissecting the engine was quite a mission, as the engine we dissected had never been touched before us.  Everybody had engines that had already been pulled apart and put back together before.

The first thing we were told to do was to time the engine.  Rob told us a little phrase called "TDC", which meant "top dead center", which means that the valves and crank was to be adjusted to the top dead center, top be worked on.   This was especially important in my case, as I was working on the head.  The valves needed to be uncompressed so that they can be removed easily.  

First thing to be removed was the rocker cover gasket.  This was very quick and easy.  Leads were pulled out and distributor was removed. I did attempt to remove the spark plugs but it was not necessary.  Inside the head was a pair of rocker shafts with rockers slotted through.  each shaft had eight rockers to push each valve down.  

Next was to remove the cam shaft.  The camshaft was removed by inserting an adjustable spanner in the bolt pattern on the shaft on the inside part of it.  A little tab was slid out to let the shaft move back and forth freely.   A socket and ratchet was connected to the bolt on the pulley and was twisted.  The shaft slid out the other end easily.

Next, the valves were to be removed.  This was the hardest part, as a clamp was needed to compress the valve springs first.  I split two tables slight apart and set the head on top so that  the valves in the center could be removed.  A special clamp was used to compress the valve springs and the small keepers were removed and the valves slid out.  

Valve stems were then measured to check for tapering and oval.  The stem was measured at three points down and then turned over to check the sides.