| Also known as | T1920 |
| Diagram | Fig. 2 — CRANKCASE · ref 40 |
| Subsystem | engine bottom |
| Listed in parts books | 1965, 1967–1968, 1970–1971, 1974, 1976–1979, 1983, 1985 |
Blanking plug
A crankcase blanking plug (Welch plug) that seals an unused machined bore, also known under the older T1920 part number.
57-1920 is a blanking plug (also called a Welch plug) that seals an unused machined opening in the case. The catalog ties it to the crankcase figure, so this is one of the freeze-plug style discs pressed into a bore that doesn't need a fitting or fastener in that spot. It's a small part but it keeps oil in and dirt out, and it's easy to overlook until it starts weeping.
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The legacy T1920 number is just the older letter-prefix form of this same part, so if your parts book or an old invoice lists T1920, that's this plug. It shows up across a long stretch of catalog years, which tells you it was a running part across a wide span of production rather than a one-year oddball.
If yours is leaking, dented, or missing altogether, it's worth pulling and replacing rather than trying to reseat it — these are meant to go in once and stay. Confirm the bore size against what's in your case before ordering, since blanking plugs come in more than one diameter depending on where they're used.
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