| Also known as | E4000 |
| Diagram | Fig. 6 — CYLINDER BLOCK AND HEAD, T100S, T100C SINGLE CARBURETTER · ref 2 |
| Subsystem | engine top |
| Listed in parts books | 1964–1968 |
Cylinder block
Cylinder block for the Triumph 500 unit twin, later superseded by 70-9719.
70-4000 is the cylinder block for the Triumph 500 unit twin engine, listed in the parts books under CYLINDER BLOCK AND HEAD figures covering the T100S, T100C, T100R, T100T, 5TA and T100SS. This is the main casting that carries the two cylinder bores, sits above the crankcase, and forms the mounting deck for the cylinder head.
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The part shows up across a run of catalog years from the mid to late 1960s under this number, and also under the older E4000 form if you're working from an earlier parts book. Triumph later revised the casting and assigned it the number 70-9719, so if your book or a supplier lists that number instead, it's the same part under its later factory identity.
Because this casting appears across several different model figure listings (single-carb and twin-carb variants among them), it's worth confirming which specific head and carb setup you're running before ordering, since the figures split by carburetor configuration as well as by model.
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