Manifolds

Please note that several different types of manifold nut are shown in this section.  The standard brass nut GHF261 is the usual fixing for manifolds - being brass it doesn't sieze on the steel manifold studs too easily.  The long brass nut 51K1177 first saw light on Mini manifolds when BMC's Competitions Department and Special Tuning wanted a manifold fixing that wasn't so fiddly to get at.  It does the job very well and is far easier to do up or undo than the standard nut, but for some reason - probably cost - was never adopted on the production line.  The steel nut alternative, FNZ105, was fitted off and on over the years (most likely as a panic measure when the production line ran out of brass nuts) but does tend to sieze on the manifold studs unless plenty of copper grease is applied.

Combined inlet and exhaust manifold

Single HS2 Carburetter Type
Manual Gearbox, 1959-74
Early 848cc Mk I Minis were fitted with a manifold lacking the boss to accept positive crankcase ventilation (PCV); this manifold has been superseded by a later design with the boss.  If your early Mini is not fitted with a PCV valve you will also need, along with the later 12A1097 manifold, an ADP210 blanking plug and 1B3664 sealing washer to seal the unused manifold boss.

Some Cooper and Cooper S models were fitted with an inlet manifold lacking the boss to accept positive crankcase ventilation (PCV); this manifold has been superseded by the design with the boss.  If your Cooper is not fitted with a PCV valve you will also need, along with one of the inlet manifolds listed here, an ADP210 blanking plug and 1B3664 sealing washer to seal the unused manifold boss.

These inlet manifolds may of course also be used to fit twin HS2 carburetter installations to non-Cooper Minis.

Through the 1960s H4 carburetters were offered by Special Tuning for Cooper S models; these fitted on the original inlet manifold albeit using different studs. By the 1970s Special Tuning had replaced their H4 package with a choice of twin HS4 (for 998cc or 1275cc models) or twin HS6 carburetters (1275cc only).

These required their own special inlet manifold, C-AEG489, which may of course be used to fit HS4s or HS6s to non-Cooper Minis.

The CAM6618 manifold may be directly replaced by the C-AHT770 item, which is also water heated but benefits from much improved flow characteristics. The vast majority of Somerford Mini customers requiring an inlet manifold for a single HS4, HS6 or HIF carburetter installation choose C-AHT770.