Location of Oil Pressure Relief Valve

John Walls · Post by **John Walls** » Sat Mar 19, 2011 10:39 am

I have a 1960 650 AJS model 31 deluxe.
I am having a problem locating the oil pressure relief valve.
There is an orifice at the end of the filter housing and from the timing side there is a metal cap that appears to blank off this orifice but there is no valve.
The engine was bought in pieces so I a not sure what should be there.
Help please.

Eric · Post by **Eric** » Sat Mar 19, 2011 11:20 am

You have found the place where it should be it seems the valve may have been removed in the past and capped off from the timing side.

If the valve had been faulty the then owner may have decided to remove it particularly as AMC chose not to fit one for some years anyway, so it may not be considered essential by some.

The bits you need are probably available from JSL and I have seen articles in Jampot about making modified versions, as its considered by some that the valve contributes toward wet sumping.

The valve definitely has a purpose as when starting from cold the oil pump can generate very high oil pressures particularly if using a mono grade oil.

So even if you have taken every precaution upon engine assembly to get the crankcase joints oil tight one moment of excess pressure can promote a leak forever.Edited by - Eric on 19 Mar 2011 11:24:46 AM

Don Madden · Post by **Don Madden** » Sat Mar 19, 2011 4:54 pm

Without a pic it is difficult to know what you found. The oil pressure relief valve indeed should be fitted into the orfice at the deep end of the filter tunnel. It is a plunger with a spring behind it & the end protrudes into the timing chest, retained by a washer & circlip. The plunger is visible in the filter tunnel & can be pushed in with a suitable tool to remove the circlip from the other end. If you see only the orfice, the plunger must be missing. A cap to seal the passage sounds like a bad idea. Cheers, Don.