|The MGA With An Attitude
Blow-Down Test Connectors - TS-212
If you find low compression on one or more cylinders you can do a blow-down test for diagnostics. You need a fitting that will screw into a spark plug port. You can make the fitting from an old spark plug, break off the ceramic, punch out the material in the center hole, and weld or braze an air line connector fitting to the remaining steel part.
For more information on compression problems see article BE-110.