How to Measure Rod Journal Clearance | Engine Building 101

Proper rod bearing clearance is essential when building an engine.
While some aftermarket bearing manufacturers offer general rules of thumb as starting points for target bearing clearances, there is no one-size-fits-all number. Things like engine type/size, operating conditions, intended application, and lubricant selection can ultimately effect the ideal bearing clearance number.
For our Project LS high-horsepower engine, which will have forced induction, we were shooting for a .0027-inch or .0028-inch number. Once you've established your target clearance, you can determine your existing bearing clearance by measuring the rod journals with a micrometer and subtracting the numbers from measurements taken with a dial bore gauge on the installed bearings. For the greatest accuracy, the dial bore gauge should be "zeroed" on the inside of the micrometer before measuring the bearing to ensure the measurement is the exact difference between the two.
In this video we'll take you through the entire process, from measuring and recording the journal size and checking the final rod bearing clearance. Follow along...
Tools Used:
Micrometer: www.summitracing.com/search/p...
Dial Bore Gauge: www.summitracing.com/search/p...
Connecting Rod Vise: www.summitracing.com/search/p...