TDC Finder

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=90 BGCOLOR="#006633" TEXT="#F7F7FF" bgproperties="fixed" background="079005a0ddvuru.png"> <div> <A HREF="http://www.vernco.com/index.htm" TARGET="_top" TITLE="http://www.vernco.com/index.htm"><U><B>home</B></U></A><B>     |     </B><FONT SIZE="5" COLOR="#FFCC66" FACE="Arial" ><B>Vern</B><B>co.com</B></FONT></div> <div> back to<B>  </B><A HREF="index.htm" TARGET="_top" TITLE="Tips and Tricks"><U><B>Tips and Tricks</B></U></A></div> <bR> <div> <A HREF="http://www.vernco.com/id173.htm" TARGET="_top" TITLE="http://www.vernco.com/id173.htm"><U><B>Site Map</B></U></A></div> <div> </div> </td> </tr><tr> <td valign="top" width=150 BGCOLOR="#669966" TEXT="#080000"> <div> <A HREF="id750.htm" TARGET="_top" TITLE="Easy Transmission Access"><U>Easy Transmission Access</U></A></div> <div> <A HREF="id310.htm" TARGET="_top" TITLE="Removing the Transfer Case Shifters"><U>Removing the Transfer Case Shifters</U></A></div> <div> <A HREF="id311.htm" TARGET="_top" TITLE="Pulling the Parking Brake Drum"><U>Pulling the Parking Brake Drum</U></A></div> <div> <A HREF="id317.htm" TARGET="_top" TITLE="Transfer Case Seals"><U>Transfer Case Seals</U></A></div> <div> <A HREF="id321.htm" TARGET="_top" TITLE="Remote Drivetrain Breather and Drain"><U>Remote Drivetrain Breather and Drain</U></A></div> <div> <B>TDC Finder</B></div> <div> <A HREF="id743.htm" TARGET="_top" TITLE="Timing Marks"><U>Timing Marks</U></A></div> <div> <A HREF="id328.htm" TARGET="_top" TITLE="Steering Bellcrank Pin"><U>Steering Bellcrank Pin</U></A></div> <div> <A HREF="id510.htm" TARGET="_top" TITLE="SemiQuick Steering Disconnect"><U>Semi-Quick Steering Disconnect</U></A></div> <div> <A HREF="id540.htm" TARGET="_top" TITLE="Windshield Latch Release Tool"><U>Windshield Latch Release Tool</U></A></div> <div> <A HREF="id397.htm" TARGET="_top" TITLE="Speedometer Lube"><U>Speedometer Lube</U></A></div> <div> <A HREF="id677.htm" TARGET="_top" TITLE="Driveline Calculator"><U>Driveline Calculator</U></A></div> <bR> </td> <td valign="top" height=390 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> Finding when a piston is at Top Dead Center (TDC) can be a bit tricky with a flathead motor.  On an overhead valve engine, including the F134 engine, use a soda straw inserted through the spark plug hole to monitor the position of the piston.  Don't use a dowel or metal rod or anything else that can break.  Don't ask how I know.</div> <bR> <div> But with a flathead, the piston is offset and not visible from the spark plug hole, so the soda straw will not work.  An old trick is to bend a piece of soft wire (copper works well) in a stairstep shape so that a short leg hangs down over the piston.  The following image, based on a cross-section scan from the service manual, shows the wire lifted up with the piston already at TDC.  Make the leg that hangs down fairly short, about 1/4", so the wire doesn't get forced against the cylinder head.  The offset at the bottom is approximately 1.25" but is not critical.  (This was for an L134 engine, others may be different.)  The extra bend at the top helps to keep track of which direction the wire is pointing inside the cylinder:</div> <bR> <div>  <A HREF="id338.htm" TARGET="_top" TITLE="TDC scan"><U><IMG SRC="5117dac0.jpg" border=0 width="125" height="172" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></U></A></div> <bR> <div> As the piston moves up, it will lift the wire.  This will provide a suitable level of accuracy for most needs.  If you need even more precision, use a turkey baster and fill the combustion chamber with oil.  Make sure both valves are closed.  As the piston moves, it will change the oil level at the spark plug hole.  Afterwards, drain the oil carefully and turn the engine over by hand a few times to prevent damage from hydraulic lock.</div> <bR> <div> Be aware that the flywheel, which has the <A HREF="id743.htm" TARGET="_top" TITLE="Timing Marks"><U>timing marks</U></A>, may not be installed correctly.  Mine was 180 degrees out, and I know of several other folks who have discovered the same thing.  It wasn't worth the effort to pull the engine to rotate the flywheel, so instead I used cylinder #3 to set the ignition timing.  The L226 engine used in later Willys trucks and wagons has the timing marks on a harmonic balancer at the crankshaft pulley.  The outer ring of the balancer has the timing marks and is prone to slippage, so you may need to use this method to find TDC on the L226 engine.</div> <bR> <bR> <bR> </td> </tr></table></body>