ET: Engine (Twin) Quieting ramps / Andrews Mk 2

[DucATIRadeon]

aluminium pushrods in the Royal Enfield give about 0.2~0.3mm clearance between cold and hot engine when using original CI cylinder barrel.
with the aluminium barrel this grows to about 0.7mm with hot engine. makes you think how much tighter the head bolt tension get at hot engine...

also the mechanical noise with a CI barrel is far less than aluminium barrel...
pushrods are enclosed inside the barrel like many brit engines were at the time.
pushrods are hollow aluminium 10mm x 2.5mm with hardened hollow tips and ¼" adjusters (the indian versions later went on to M6 adjusters somewhere early this millennium). length is about 225mm exhaust, 215mm inlet.
then later models went to ball-tipped pushrods.

 

[oexing]

Thank you, that is exactly my thinking: I believe most cylinder studs get way too much torque by owners which does not help in some more matters. The air head BMWs from 1969 got very long studs , solid M 10 threads from case to head, rocker brackets and all alu engines. They seem to wreck case threads quite often by brutal force, likely because heat growth will add to the tension in the ht steel studs with half the extension factor than alu. So really keep forces on the spanner a bit milder as strain on the threads will mount when heating up.
Stainless steel would help a bit with added extension but then suitable lubrication of threads is essential for preventing seizures - and many owners turn out to be very ignorant or forgetful about lube on fasteners. So better not have stainless for avoiding complaints from stupid . . .

Vic