Using a leakdown tester is one of the best ways to assess the health of your engine.
Easy to use, a leakdown tester measures how much cylinder pressure is escaping from your cylinders, showing how efficiently your piston rings and valves are sealing the combustion chamber, along with your head gasket. With street engines, ten to twenty percent leakdown is typically acceptable. For race engines, the acceptable leakdown is one to ten percent.
If you have one or more cylinders that have out of spec leakage, this points to a problem with sealing in the engine and usually requires disassembly to properly diagnose and repair. If you’ve just built a motor, doing a baseline leakdown test before it has run is ideal, so you can track your engine’s performance and wear over time.
Here’s how to do a leakdown test of your engine: