| Also known as | E3745 |
| Diagram | Fig. 5 — CYLINDER BLOCK AND HEAD, T90 · ref 23 |
| Subsystem | engine top |
| Listed in parts books | 1964–1970 |
Inlet rocker box
Inlet-side rocker box housing for the smaller unit Triumph twins' cylinder head valve gear.
70-3745 is the inlet rocker box for the smaller unit-construction Triumph twins, sitting up top on the cylinder head where the rocker gear for the inlet valves lives. It's the housing that carries the rocker shaft and rockers for that side of the head, bolted down over the valve gear so the pushrods can do their work and oil can find its way through the top end.
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This one turns up across the cylinder block and head listings for the 3TA, T90, T100S, T100C, T100R and T100T, so it was a common casting across that family of smaller twins through the second half of the 1960s into 1970. If your parts book uses the older E-prefix numbering, this is the same part as E3745.
Rocker boxes take a beating over decades of heat cycling and take-apart/put-back-together during head work, so it's worth a look at the mating surfaces and shaft bore before bolting a used one back on. Bring your old box in or give us a call if you want to talk through what shape yours needs to be in before we send one out.
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