Correct set of cylinder base studs for the early unit-construction Triumph 350 and 500 twin-cylinder models. The set includes (6) of the 70-3820 and (2) of the longer 70-3819 studs, which were used with the cylinder barrel dowels.
Manufactured to exacting factory specifications by LF Harris in the UK, the studs are threaded to 3/8″-20 TPI for fitment to the cylinder base, with 3/8″-26 TPI CEI. The 70-3820 studs are 1-1/2″ long and the 70-3819 studs are 1-11/16″ long.
The studs are anchored into the crankcase cylinder base and retain the cylinder barrel. Alignment dowels are used on the (2) longer studs.
The studs are threaded into the cylinder base by using (2) 3/8-26 TPI nuts tightened together to form a bolt head, a technique known as “double-nutting”, which allows the studs to be securely locked down into the cylinder base. The nuts are then removed before fitting the cylinder barrel.