| Also known as | E5946 |
| Diagram | Fig. 6 — CYLINDER BLOCK AND HEAD · ref 16 |
| Subsystem | engine top |
| Listed in parts books | 1966–1970, 1974 |
Inner valve spring
Inner valve spring for Triumph 3TA/5TA/T90/T100 cylinder heads, works with the outer spring to control valve motion.
70-5946 is the inner valve spring used in the cylinder head assembly on Triumph's smaller unit-construction twins. It's one half of the dual-spring setup at each valve, working alongside the outer spring to keep the valve seated and under control through the opening and closing cycle.
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This part number shows up across a run of cylinder block and head figures covering the 3TA, 5TA, T90, and T100 family (including the single and twin carburetor T100 variants), so it's a common item on these smaller-bore engines. The legacy E5946 stamp is the same physical spring under the older numbering.
Valve springs are a wear item — they lose tension over years of heat cycling, and a weak inner spring can let valve float creep in at higher revs. If you're doing a head rebuild, it's worth checking free length and tension on both inner and outer springs rather than assuming they're still good.
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