Oil pressure release valve

[zidz]

Hi guys,

I have ordered a new spring and ball for my OPRV and when I disassembled it I have found out that spring is different (see the picture - new spring is thiner).

It was ordered from Draganfly - here are parts numbers:
67-1496 Oil valve spring Superseded to 10374-54


I will use old spring, but just for information, can be new type used? Does have anyone experiences with that?

Thank you
Zdenek

[TTJOHN]

I switch over to the Triumph oprv I think it's better, it's a plunger type instead of a ball and I believe it's set at 15lb.

TTJohn

[DAVE BRADY]

Hi,

Providing the new spring offers the same resistance and blows off at about 50psi it will be fine.  Call Draganfly for clarify.
I too prefer to replace with the later piston type rather than the ball but using stainless A65 one from SRM.

Dave.

[Roy]

There's another mind field regarding the PRV , I have had a test rig ,and found certain new valves leaking at  around 20 lbs , not only though spring pressures. But  also the OD of the threaded part that screws into case being under size ,allowing oil to pass by threads ,

[DAVE BRADY]

Hi,

I think that the SRM one is made to the exact BSA spec. and sometimes will not screw in the case.  The reason behind this is that as the tap used in the factory became worn it did not cut the 'blue print' size hole and the thread in the case was smaller with the prv being made to fit regardless of the wear on the tap and hence the thread in the case. So it follows that when a new tap was used the the prv could well be loose in the case.  It would not surprise me if the issues mentioned by Roy existed from the start. It is likely that pattern parts are made to this 'fits all' size as well as poor internal fit.
SRM will lend the appropriate tap to clean the thread in your case so that their correct (?) size prv will fit.  I did this with spot on results.

Dave.

[Allan G]

Ive been fortunate with OPRV threads upto now, but I think a lot of issues will be more likely from previous ham fisted owners over tightening the fitting in order to get it to seal. Thus distorting the threads.

Having seen 3x SRM OPRV units which have score marks on the pistons, I refuse to use them. My thunderbolt has the A70/A75 70PSI OPRV available from LF Harris. I have a piston type 50PSI unit on my Lightning which I bought a few NOS from the states some years ago. I strip and clean them up before fitting. Again, they have been very good.