Measurement Tools For Engine Builders
Serious engine repair requires quality measuring instruments. These include micrometer, digital caliper, dial indicator, dial bore gauge, small hole gauges, and of course, a feeler gauge!
******************
Outside Micrometer
The most common outside micrometer size for engine building is one with a 0-1" Measuring Range.
Also common is one with a 1-2" Measuring Range.
******************
Digital Caliper
Digital calipers are more expensive than vernier or dial calipers, but they are easier to use and quicker to read.
For complete article on Best Digital Caliper For Engine Building click here.
******************
Dial Indicator With Magnetic Base
Having a dial indicator allows you to check end play, flywheel run-out, up-and-down movement on connecting rods, and many others. Most have increments of .001" on a 0" to 1" scale. They can be mounted by clamp or magnetic base.
In the picture above, I'm checking thrust clearance on a Harley 45 Flathead with magnetic-base dial indicator.
******************
Bore Gauge
To accurately measure the inside diameter of a cylinder, a dial indicator bore gauge is needed.
Most will have a range of two to six inches, a depth of six inches, with a round dial of .001" increments.
Here I'm checking the bore diameter of an Ironhead Sportster cylinder.
******************
Small Hole Gauge
To accurately measure the inside diameter of valve guides (and other small bores), a small telescoping gauge is required.
These are also called small-bore gauges, and come in varying sizes.
******************
Feeler Gauge
A feeler gauge, or gap gauge, is needed for checking valve tolerances, ignition point gaps and other critical measurements. They're made up of thin metal blades. Each blade is a different width of precise thickness, and will be marked in either thousandths of an inch, or millimeters, or both.
Measuring valve lash on a Kawasaki XZ650.
The blades usually range from .0015" to .035" (.038 to .889mm) in width. And if needed, you can also pair two blades together.
Long feeler gauges may be required for valve adjustments on some engines.
******************
Double Checking/Practice Measuring
Engine clearances are critical, not only for maximum performance, but also for long, trouble-free service. Learning to correctly read precision instruments takes practice. First-time builders should measure a dozen times (or more) before trusting their readings.
Machinists who have years of experience still double-check their specs.
Remember that micrometers, dial indicators, and dial bore gauges are precision measurements, and need to be treated as such. For consistent and reliable results, keep them clean and out of harm's way.
******************
Related Articles: