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Home Made Leakdown Tester

Written by otherbrother

Monday, 13 November 2006

  • Parts required:
  • 1, used spark plug with good threads. Plug will need to be correct for your desired use.
  • 1, air presure regulator.
  • 1', of 1/8" or 1/4" presure hose rated for your intended use ( most home compressors are rated between 150/180 pounds working pres.).
  • 4, hose to pipe nipples sized for the hose and regulator you have.
  • 4, hose clamps.
  • 2, male quick connect ends sized to the style you are going to use.
  • 1, female quick connect of the same size.
  • 1, presure guage if you desire, not required.


Remove end electrode from plug, being careful not to damage threads. Remove center from spark plug, best done by chipping ceramic away with a small punch or chisel and hammer. Silver solder, braze, or weld one of the male quick connects to the insulator end of the now hollow plug shell. Cut your hose in half, attaching nipples to each end. Thread one end of each hose into the regulator and put the remaining quick connects on one of each hose ends. Install the guage in the regulators guage port if you are going to use one and thats it.....


Be sure to back the regulator off to its closed or lowest position before useing. Bring the cylinder you want to check to it's TDC position, screw in the adapted spark plug shell and attach the quick connect on the regulated line. Hook up your presurized air supply and open your regulator slowly.

Listen at the tail pipe for noise of air escapeing past the exausht valve, throttle bore for an intake valve leaking and rocker cover port for ring leakage.

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