Alex's Parts Carries a line of steel pipe plugs for general automotive use.
These little gems won't be found at your local parts house or hardware store.
This size is common for Big Block Chevy 454 blocks.
Most 454 blocks use these on the side of the block where GM drilled oil holes to feed the main bearings.
Oddly enough, freeze plug kits for BBC come with 1/4" plugs which fit 396/427 blocks but many 454 blocks use 1/8" plugs.
This kit come with five plugs which is enough for most 454 blocks.
Pipe plugs always appear larger than their size suggests.
This is because the size grading is based on the inside diameter of the pipe, not the outside diameter of the thread.
A 1/8" pipe plug is intended to screw into a threaded hole which would accept a pipe with a 1/8" inside diameter.
Specs: