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Tuesday, November 5, 2013

T100R top end assembly

The cams and timing gears are installed.  The Daytona cam timing specifications differ from the other T100 models which is why the cams are installed using the dashes rather than the dots.

  I lightly chamfered the backside if the cam gears in order to ease their installation.

 I also had to replace the intake cam due to some "mechanic" in the past using a hammer to install the gear and causing large chips on either side of the key slot.  Always use the proper tool for removal and installation of the timing gears.
The proper tool:


 The WRONG tool:

Pistons, tappets and cylinders are installed as are the timing gears.  Now I will install the degree wheel and pointer along with a dial indicator in order to precisely locate top-dead-center (TDC) in preparation for checking piston-to-valve clearance at TDC of the exhaust stroke, which is the overlap period where the exhaust valve and intake valve are both open.  During this period of crank rotation the exhaust valve has not fully closed, while the intake is starting to open.  It is at this point that the valves will be in closest proximity to the piston.

 To find TDC the degree wheel is mounted to the crank at roughly TDC and the dial indicator is mounted to the cylinder deck surface and set to zero while contacting the piston crown.
The pointer is adjusted until the degree wheel reads the same number of degrees on either side of the TDC mark with the piston .050" down in the bore.


 Now that TDC is accurately established, I install an intake and exhaust valve with lightweight checking-springs and temporarily assemble the head onto the engine with gaskets, pushrods and rockerboxes.  The valve adjusters are set to zero lash with the piston at TDC on the compression stroke and the dial indicator is set up on the head.

  Then the engine is rotated forward 360 degrees to TDC on the exhaust stroke and the dial indicator is set to zero while bearing on the valve adjustment screw.  Now the exhaust valve rocker is depressed until the exhaust valve makes contact with the piston while observing the amount of travel on the dial indicator.  The minimum piston-to-valve clearance is .040".  Since this engine was built with stock valvetrain components and pistons the clearance was not an issue, but it always pays to be sure, especially when dealing with a head that needed to be straightened and trued.
 Then the process is repeated for the intake side.

Now the actual valve springs can be installed and final assembly of the top end can commence.

You might have noticed the intake "manifolds", they are the stock pieces machined for spigot-mounted carbs.  No, the owner doesn't want Amals.