| Also known as | E3740 |
| Diagram | Fig. 6 — CYLINDER BLOCK AND HEAD, T100S, T100C SINGLE CARBURETTER · ref 16 |
| Subsystem | engine top |
| Listed in parts books | 1964–1968 |
Inner valve spring
Inner valve spring for the cylinder head on 3TA, T90, and T100S/T100C engines, part of the dual valve spring setup.
70-3740 is the inner valve spring off the cylinder head, part of the double valve spring setup used on these engines. The catalog carries it under the old E3740 number too, so if your parts book lists it that way, it's the same piece. It shows up in the cylinder block and head listings for the 3TA and T90, and separately for the T100S and T100C, so it's a spring that's been used across more than one small-twin head configuration.
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On a head running dual valve springs, the inner spring works alongside an outer spring to control valve closing and help resist float at higher revs. When you're doing valve work, it's the kind of part worth replacing as a set with its cup and outer spring rather than reusing old ones, since fatigued springs are hard to spot by eye.
We don't have extra dimensional or material specs on file for this one beyond what's in the parts book, so if you need exact free length or wire spec, give us a call and we'll walk through it with you before you order.
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