Operating Instructions 8 SG9M Manual
Selection of the Pilots
Choosing the right pilot will ensure the accuracy of the machining.
The pilot is selected according to the actual guide and not according to the original guide diameter or the
valve stem diameter.
See below for a guide how to select the proper pilot for the application
Rottler Live and Fixed Carbide Centralizing Pilots are manufactured from fine grain sintered tungsten
carbide and are ground to a very high degree of accuracy, straightness and surface finísh - designed for
a life time of precision machining!
The part number of the pilot represents the actual diameter of the straight/parallel part of the pilot where
the pilot fits into the valve guide.
For example:
FCP0700 means that the diameter of the part of the pilot that goes into the valve guide is 7.00mm
(0.2756”)
FCP1270 means that the diameter of the part of the pilot that goes into the valve guide is 12.70mm
(0.5000”)
The pilot is the only link between the fixed part - the clamped cylinder head and the moving part - the air
float machine workhead. The centering and the machining accuracy depend on the use of the correct
pilot. The pilot is selected according to the actual valve guide and not according to the original guide
diameter or the valve stem diameter, the pilot is ALWAYS larger than the valve stem diameter.
Pilots are available in increments of .01mm (0.0004”). For practical purposes, it is best to select a pilot
that is a small amount less than the nominal size of the valve guide, approx .01mm (0.0004”) is
recommended between the pilot size and the valve guide nominal size, this clearance allows the pilot to
enter all the guides in a cylinder head as some valve guides may be smaller than their minimum
tolerance.
Most new valve guides are manufactured to a nominal size such as 7mm or 11/32” and the valve stem
diameters are manufactured to be smaller than the nominal size to allow clearance for heat expansion of
the valve stem when the engine is operating. For example: a 7mm valve guide has an internal diameter of
exactly 7.00mm (.2756”) The valve stem diameter of the intake valve is 6.98mm (.2748”) and the exhaust
is 6.96mm (.2740”). In order for the pilot to fit most all valve guides, the first choice could be FCP0699 to
give .01mm (0.0004”) clearance. If the valve guide is used and has some wear, then the second choice of
pilot could be FCP0700(0.2756”).
The pilot can also function as a GO-NO GO gage, in other words, if the pilot does not enter the valve
guide, the valve guide may be too small which could result in too little running clearance between the
valve stem and valve guide which could result in seizure and major engine failure!
Rottler makes 3 sizes of shanks of pilots:
1. 6.00mm (0.2362”) for small valves guides 6mm (0.236”) and below. The part number for these
pilots is FCPM.
2. 0.375” (9.52mm) for common size valve guides, 6-14mm (.236-.625”). The part number for these
pilots is FCP.
3. 20mm (0.7874mm) for large valve guides for SG80A machine. These pilots are made to order
specifications.
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