| Diagram | Fig. 5 — CRANKCASE · ref 12 |
| Subsystem | engine bottom |
| Listed in parts books | 1970 |
BSA Stud barrel to crankcase (5/16" Unified Fine/Unified Coarse × 1-7/16")
A 5/16 in. UNF/UNC barrel-to-crankcase stud, 1-7/16 in. long, for clamping the cylinder block to the crankcase.
This is a barrel-to-crankcase stud, the kind of fastener that ties the cylinder block down to the crankcase mouth so the two castings clamp together tight. It's threaded 5/16 inch, Unified Fine on one end and Unified Coarse on the other, at 1-7/16 inches long, which tells you it's meant to thread permanently into one casting while a nut clamps the barrel down on the other end.
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The catalog data we have on this one places it in the crankcase figure with just a single appearance, dated to 1970. That's thin coverage, so we'd rather be straight with you than guess at which specific engine family it belongs to.
If you're rebuilding a bottom end and need to confirm this stud matches your casting pattern, give us a call before you order. We can talk through what you've got on the bench and make sure the length and thread combination lines up.
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