ok so my A65 bitsa has 66 cases and flatfaced/ball type OPRV....the OPRV on my pal calvin's 72 A65T had domed face and piston innards...so does the OPRV on my 72 T120....ok..so are Triumph and late BSA OPRVs interchangeable with early ball type??? just ponderigng another bit of tinkering but dont want to open a can o worms PS I see lots o the Triumph domed type on eBay some new some used
The BSA OPRV opens at 50psi, the Triumph at 60psi. As I recall, the SRM opens at 60psi (one reason it results in better oil pressure?) The one you really don't want is the OPRV for triples. That one opens at 75psi.
Raf, I took a domed one out of a late b44 or B50 I think. Could not see why it would't work. I was not much concerned about 50, 60 , or 75 psi. I want 40 psi cruising and at least 10-20 at idle and so far I have it.
What is a safe operating pressure? Modern cars run about 70 maybe 75 psi. I am not so concerned about my bush as it is a much harder material that the original Vandervell. The rods have aftermarket shells. Early bearings were soft to provide embedability so grit would not damage the crank. With modern filtering systems, is that any longer important??? I dunno!
BSA seemed to use Whitemetal bearings which are soft and need greater protection from cavity erosion caused by excessive pressure, both Triumph and Norton look to have used Copper lead plated with lead indium which is a stronger base material with a very thin soft surface so need less protection.
So if you use the Glacier replacements you can go to 60 psi on a BSA.
I am sure the whitemetal in the A65 was a partial cause of the problems the A65 is percieved as having as the margin for error is decreased in the oil supply by using a soft bearing material as it overheats easily once the oil layer in the bearing is compromised.
The B25 Unit Single bearings I have seen out of old engines are Whitemetal too, can only think this was BSA purchasing in league with Vandervell whose only option if forced to provide a cheaper bearing than the proper VP2 Trimetal had to supply Whitemetal (babbit) as they did not have the Aluminium/Tin technology in the 60's, they finally got Al/Tin in the 80's when they bought a bearing factory in Italy.