| Also known as | E4700 |
| Diagram | Fig. 1 — CRANKSHAFT AND CONNECTING RODS · ref 35 |
| Subsystem | engine bottom |
| Listed in parts books | 1964–1966, 1968–1969 |
Tachometer drive thimble
Tachometer drive thimble that engages the exhaust camshaft to drive the tach cable train.
70-4700 is the tachometer drive thimble, a small fitted piece that mounts on the exhaust camshaft to engage the tach drive gear train. It shows up in the parts book under the CRANKSHAFT AND CONNECTING RODS figure, which tells you it lives down in the timing chest area where the cam meets the drive train that eventually runs your tach cable up to the instrument.
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If your parts book is older, you may see this same piece listed as E4700 - that's the legacy number for the identical part before the modern numbering came in. Catalog appearances run from the mid-1960s through the end of the decade, so it's a part that saw plenty of use across that stretch of unit-construction twins.
It's a small, low-cost item, but it's not one you want to overlook if your tach isn't reading right - a worn or missing thimble is a common cause of erratic or dead tachometer drive. Worth keeping a spare in the parts drawer given how easy it is to lose track of when the timing chest is open.
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