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Thread: RSR oil pressure relief valve

  1. #1

    RSR oil pressure relief valve


    Could anyone tell me at what pressure the later, non-adjustable valve should open? I originally thought that it was around 5 bar, but someone is telling me between 10-12 bar. This seems extremely high to me, but I'm certainly no expert. Thanks.

  2. #2
    10 bar is almost 150 psi. Given that I see 120 psi peaks on start up in my normal 911, the 10 bar sounds about right. My relief valve seems to come in around 100 psi after a few seconds of running.
    1971 911S, 2.7RS spec MFI engine, suspension mods, lightened
    Early 911S Registry Member #425

  3. #3
    I thought that I'd also post a couple of pictures from Armando's site of the valve I'm talking about. The p/n is 901.107.017.00.
    Attached Images Attached Images   

  4. #4
    Senior Member Grady Clay's Avatar
    Join Date
    Sep 2004
    Unincorporated Arapahoe County, Colorado, USA
    I have never found a specification but it calculates to be about 100 psi and measures in that range.

    One key is to have the shortest and least restrictive path for the pressure-relief oil to get from the engine outlet to the oil tank.
    If you measure pressure spikes at 150 psi at the engine outlet, the additional 50 psi is from flow restriction to the tank.

    All this is important as the scavenge pump must pump 100% cold oil on start-up after setting.
    If this oil is forced to a front cooler without an over-pressure escape, the pressures can exceed the safe pressures for the cooler.
    There is no over-pressure protection relief valve in the engine for the scavenge pump.
    In normal running operation this pump sees about 60% oil and 40% entrained air.

    I think the only production 911 with a front cooler but without the pressure relief valve is the ’73 model, including the RS.
    The ’73 was successful because all had the ‘trombone’ cooler and able to withstand the over-pressure.
    Issues appear if the trombone is replaced with a full-fin cooler.

    There is a lot of discussion of these issues on Pelican.


  5. #5
    Thanks, Grady, I've posted the same question on Pelican as well, but yours is the most in-depth reply so far. I did a lot of searches on the various forums but couldn't see my question discussed. Apologies if I should have been able to find the answer.

  6. #6
    Senior Member
    Join Date
    Aug 2003
    Van Nuys, Ca
    So who is building an accurate working replica of this valve? Inquiring minds want to know !
    Member #755
    Conda Green 70 911S
    70 black 914-6 3.2
    70 911 "Speedster" project
    "74 IROC" tribute Jade Green RSR

  7. #7
    repo 950 euro
    Attached Images Attached Images  
    Jeff H.
    72 911
    914-6 GT

  8. #8
    Quote Originally Posted by JKH View Post
    repo 950 euro
    That's the one I've been told opens between 10-12 bar, supposedly like the original, but as I first posted, I found this high. While outwardly it looks like the original, I'm trying to figure out if it is indeed an accurate working replica or not. Is anyone using one of these or know who actually makes them?

    Quote Originally Posted by varunan123 View Post

    makes one i can live with
    Eric's adjustable valve, which although not an exact replica of the original, earlier adjustable valve in appearance, performs the same function to protect the oil cooler and comes pre-set at 75 PSI, or around 5 bar, for example. Could anyone using that valve please tell me at what pressure they have it adjusted to pop-off?

  9. #9
    Vintageracer John Straub's Avatar
    Join Date
    Sep 2006
    La Quinta
    Here's the original one on my GT...never have had a problem.


    Sorry for the small image, I don't know what happened.
    1965 911 #301111, Red Book Vol 1 "Cover Car," owned 53 years.
    1967 911 #307347, bare-bones, some road wear, a little surface rust, and a few dents..., owned 13 years.
    1970 914/6GT, (Sold - ran the last three Rennsports)owned 30 years.

    Photography Site:

    Registry #983
    R Gruppe #741

  10. #10
    I make the adjustable ones for Eric, I prefer a lower pressure , may even warm up faster.
    1- I am not racing,
    2- I would rather bypass than risk a cooler, (not everyone has a Behr rated @10bar. and being 40
    years old may not be up to par.)
    3- Behr coolers have a built in bypass
    4- Most important, The later valve is generic looking , I love knobolgy.

    The PMB valve is re machined from a commercial hydraulic valve that list for over $ 300 , I modify
    the appearance only, with cost effectiveness in mind , Trying to keep the visual appearance near
    the factory part.

    Wild Bill;
    I have a repo as in the picture I will test the pressure today and report back.
    I never checked it because I didnt care. I wanted an adjustable one .
    Jeff H.
    72 911
    914-6 GT

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