| Also known as | E3749 |
| Diagram | Fig. 6 — CYLINDER BLOCK AND HEAD · ref 39 |
| Subsystem | engine top |
| Listed in parts books | 1964–1970, 1974 |
ROCKER (right exhaust, left inlet)
Exhaust-side (right) / inlet-side (left) rocker arm for the cylinder head on Triumph unit-construction smaller twins, also known by its older E3749 number.
70-3749 is a rocker arm for the cylinder head on Triumph's smaller unit-construction twins. The catalog description pegs it as the exhaust rocker on the right side and the inlet rocker on the left, which tells you where in the rocker box it sits and which valve it works. This is the same part carried under the older E3749 number if you're working from an early parts book.
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The rocker arm pivots on the rocker shaft inside the rocker box and transfers motion from the pushrod down to the valve, so it's a wear part that lives in a fairly hot, fairly stressed corner of the engine. Given how many head configurations this number shows up under in the parts books, it's clearly a part Triumph carried across a run of the smaller twins, but we'd want to see your actual head and rocker box in front of us before confirming exact fitment for your machine.
If you're rebuilding a head, it's worth pulling all four rockers and checking the shaft and rocker bore for wear together rather than replacing this one in isolation. Give us a call if you're not sure which rocker position you need.
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