Sunbeam Alpine: Pressure Relief Valve PRV Comparison and modification

[@brianmorris1632]

The symptoms of a failed open PRV were exactly what happened to me (sudden zero oil pressure). I towed the car home and will look at this. Thanks guys!

[@TheSunbeamAlpineChannel]

Hi Brian, good luck with it. Don’t take any chances with a sticking PRV, replacements are available from the specialist suppliers and you can modify them as per the video if you wish.

[@tonyzuiderwyk5652]

Thanks for your video(s). I'm modifying my valve and the recommended tapping drill for 7/16 UNF is 25/64. I also note that the spring will not come out with your recommended 23/64 hole (but will with a 25/64 drill). Hope this adds to your otherwise excellent video.

[@TheSunbeamAlpineChannel]

Hi Tony, as with all our videos we simply show what we did. If there is a better way to do it we always encourage people to try that.

[@hsbhachu3d]

Few things. 1) this is a later Hillman Hunter or arrow series valve. 2) Alpine or series valves were different and half brass. 3) optimum pressure as per manual is 45psi cruising and about 20/25 at tickover. So you overdid it. 4) most alpine people don't have the Hunter valve so very different for them. 5) I've learnt to believe that not everything on the internet is accurate no matter how much one thinks they're a God.

[@TheSunbeamAlpineChannel]

We are not sure if you have watched all of the video but: 1/ it clearly states that this Alpine has a Hunter engine block and oil filter housing in the comparison section. 2/ Alpines actually had six different pressure release valves made with various materials in the nine years of production, various others were used by subsequent Rootes and Rootes derived 1725cc engines. Several different versions of Rootes PRVs are shown in the video. 3/ We deliberately raised the oil pressure as shown. Some racers take the pressure ups to extreme levels, we don’t do that but in general prefer to see oil pressure slightly on the high side rather than low. 4/ We are not sure why you think it is ‘very different’ for an Alpine. The principles for modifying the Rootes PRV are the same for all types. We’ve done this on all manner of Rootes PRVs made of various materials for 40 years, it is a proven modification and works well. 5/ ????