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Sunbeam Alpine: Making an Adjustable Oil Pressure Relief Valve (PRV)

Tim R

Silver Level Sponsor
This video shows a comparison between different oil Pressure Relief Valves (PRVs) and the modification that we make to the standard PRVs on our Alpines. This simple modification overcomes one of the weak points on Rootes engines of low oil pressure (LOP).
This isn't an original idea for us, many people have done this before in a wide variety of ways and there is a lot written about how to do this on the internet. It was also detailed and recommended in the very first UK owner's club 'Alpine Guide' publication.

The video simply shows what WE do and the effect that it has on oil pressure in our engines. We first did this in the 1980s, it is a tried and tested way of increasing the oil pressure in your engine.

It won't make a worn out engine new again but if you have low oil pressure this is a way to increase it and get some more life out of your engine before you rebuild it.
Tim R

 

Shannon Boal

Platinum Level Sponsor
Nice bit of home-brewed machining on the adjustable valve. More oil pressure and increased flow could help with oil's job of cooling things. Of course, low oil pressure may be caused by excess clearance (wear) in the main bearing, the cam bearings, or the oil pump. Now, if one is building a hot motor, then maybe 60 PSI Max is better than 45 PSI Max, although it takes power to increase the pressure. When building said motor, you could fit bearings to minimum clearances. I like about 0.002" for mains, though not much can be done to minimize new cam bearing's clearance. Funny thing, I heard somewhere that Formula one cars don't run high oil pressures. Anybody know about that?
 

Barry

Diamond Level Sponsor
Oil pressure
Nice bit of home-brewed machining on the adjustable valve. More oil pressure and increased flow could help with oil's job of cooling things. Of course, low oil pressure may be caused by excess clearance (wear) in the main bearing, the cam bearings, or the oil pump. Now, if one is building a hot motor, then maybe 60 PSI Max is better than 45 PSI Max, although it takes power to increase the pressure. When building said motor, you could fit bearings to minimum clearances. I like about 0.002" for mains, though not much can be done to minimize new cam bearing's clearance. Funny thing, I heard somewhere that Formula one cars don't run high oil pressures. Anybody know about that?



Roller bearings.
 

Shannon Boal

Platinum Level Sponsor
Hard to find info on this stuff, but here is a photo of Cosworth's "CA" motor
 

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husky drvr

Platinum Level Sponsor

Barry

Diamond Level Sponsor
Roller bearing, now that is a good Alpine topic, rocker arm tips, lifters, even saw an engine in F1 with cam bearing needle bearings. Any sources for Alpine roller-tip rocker arms?


I was not referring to roller (tip, trunion or both) rocker arms or roller lifters; both of those applications are "splash" rather than pressure lubricated and have nothing to do with oil pressure. Regarding power increase from "roller rockers", see Engine Masters, Season 2, Episode 29.
 

Shannon Boal

Platinum Level Sponsor
I was not referring to roller (tip, trunion or both) rocker arms or roller lifters; both of those applications are "splash" rather than pressure lubricated and have nothing to do with oil pressure.

I know, Barry, but the only info I can find is that F1 uses plain bearings. (That photo shows main and con rod bearings....) I guess that we were circling the question of whether higher oil pressure protects better.... and the mysteries of the hydrodynamic wedge, which can carry a bearing load of thousands of pounds, while fed with thirty PSI oil. And, then there are all those engines which were "splash-fed", no pressure involved. So, it seemed more productive to look at rocker arms......
 
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