| Also known as | 58T, E3798 |
| Diagram | Fig. 6 — CYLINDER BLOCK AND HEAD · ref 1 |
| Subsystem | engine top |
| Listed in parts books | 1960–1962, 1964–1966, 1968–1970, 1974 |
Cylinder base gasket
Cylinder base gasket for the smaller unit-construction Triumph twins, sealing the barrel-to-crankcase joint.
This is the cylinder base gasket, sitting between the base of the cylinder block and the crankcase mouth on the smaller unit-construction Triumph twins. It seals that joint so oil stays where it belongs and compression doesn't leak past the bottom of the barrels. The figure titles it shows up under cover the 3TA, 5TA, T90, and T100 family cylinder block and head assemblies, so it's a part tied to that line of engines rather than the 650 or 750 twins.
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Older parts books list this under 58T, and it also appears as E3798 in some catalog listings - same physical gasket, just different eras of numbering. The factory record shows it superseded an earlier part, 70-6923, so if your book or an old parts bag shows that number, it's the same gasket you're after.
This is a wear-and-tear item that gets replaced any time the cylinder block comes off, whether that's for a rebore, ring job, or just to check things over. Worth having a fresh one on hand any time you're splitting the barrels from the case.
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