1951 A7 pressure relief valve

[Rex]

Hi all, many A7/10s seem to have the dome-headed Triumph type PRVs fitted in place of the flat-topped item my engine has. I have a nice spare ex-Trumpet unit to use if they're compatible.
I know the BSA has a ball and spring (BSA loved their balls and springs) whereas the Triumph has a spring and piston, but has anyone actually done the swap?

[muskrat]

G'day Rex.
I haven't but quite a few have.
https://www.a7a10.net/forum/index.php?topic=12120.msg94825#msg94825
Cheers

[JulianS]

I fitted an SRM PRV some time ago and very happy with it.

You do need to be careful if you fit a piston type PRV if you do not know what it was originally made for.

There are a least 3 types;

Twin and earlier unit single type set a 50 PSI blow off pressure

Triple type set at 70 PSI blow off

Late unit single set at 75 PSI blow off.

BSA issued some service sheets as photos.

[Rex]

To answer my own question, SRM apparently supply the same item for A7/10s and a whole range of triumph twins, so it looks like they're interchangeable.

[RichardL]

If you are sure you have the Triumph vs. A10 version,  a call to Gary Hearl at SRM would settle the question as to if they are equivalent in function.

Richard L.

[Greybeard]

My bike engine is using the SRM piston style PRV.