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Oil Pressure

Discussion in 'Factory Original Alpines & Tigers' started by kam41851, Apr 12, 2012.

  1. alpine_64

    alpine_64 Donation Time

    Barry,

    On SV the above will be relevant, but the 1725 SV was the only Alpine that came with an oil cooler stock.

    They were available as options in the special tunning kit and also used on the HLM... But id guess 90% of alpines dont have them.... Whcih given the amount of alpines now running 1725s is somewhat interesting.
     
  2. Barry

    Barry Platinum Level Sponsor



    Michael,

    The OP asked about "1725 engine oil pressure" and his profile indicates a S-V.

    The fact that earlier Series Alpines did not come stock with an oil cooler has nothing to do with the OP's question or my response.
     
    Last edited: May 10, 2019
  3. Bill Blue

    Bill Blue Platinum Level Sponsor

    Has anyone mentioned the importance of validating the accuracy of a 50 year old dash gauge?

    Bill
     
  4. phyrman

    phyrman SAOCA Secretary Diamond Level Sponsor

    A friend of my Dad had a Bugatti Type 37A racer. It too suffered from low oil pressure. Then he checked the gauge!
    An easy check is to use another gauge to compare before taking things apart
    Also, clean out the copper tube.

    BD
     
  5. Barry

    Barry Platinum Level Sponsor


    That is a very good point. I would expand it to include validating the accuracy of a new oil pressure gauge / oil pressure sender system.
     
  6. 65beam

    65beam Platinum Level Sponsor

    I'm sure you know that there's a world of difference between the cooler used on a series 5 versus the optional cooler. I've always wondered how much drop in oil temp there was with the single tube cooler of the series 5 and how much drop of temp using the radiator type of the optional cooler. The series 5 cooler should get more air flow across it versus the optional cooler being tucked up under the hood hinge panel. Other cars such as an MGB used a similar cooler to the optional unit but it was in an area of higher air flow. The arrow range used the 1725 but no cooler on either the single carb version or the dual carb version. One big difference we have today is the current spec oils can tolerate a much higher oil temp without seeing a viscosity break down.
     
  7. alpine_64

    alpine_64 Donation Time

    The alloy head fastbacks did away with the oil cooler but gained the alloy sump to help cooling.
     
  8. 65beam

    65beam Platinum Level Sponsor

    It's now been 50+ years since Rootes dropped the oil cooler that was used on the 1725. In that 50+ years there have been many ,many upgrades made to the engine oils. The API category for engine oils when these cars were being built was SB. We're now up to SN. To meet that spec oils have to meet tougher standards which include using shear stable viscosity index improvers, detergents, dispersants, corrosion inhibitors, antioxidants, foam inhibitors and anti-wear additives. Anti-wear additives have never been removed from engine oil, only reduced. There is no other anti-wear additive for engine oils. All of the much improved additives are added to a base stock that is so highly refined that it looks like water. The running temp of todays vehicles is well above what the Beams running temp is. Todays conventional engine oils are blended to withstand these high temps under normal driving conditions with synthetics (either blends or full synthetics) being able to withstand much higher temps without breaking down and reducing lubrication. If a 1725 is running an engine temp of 180 and the current oils are blended to withstand the engine temps of todays engines do you have to have an engine cooler on our Beams?
     
  9. Bill Blue

    Bill Blue Platinum Level Sponsor

    If an Alpine is running with a coolant temp of 180, what is the oil temp?
    Bill
     
  10. 65beam

    65beam Platinum Level Sponsor

    Bill,
    I'm sure you know the oil temp will vary depending on operating conditions. It would be impossible to say the temp is xxx. That's the reason I carry an infra red gun for checking various temps and follow OEM's specs for lubes.
     
  11. Barry

    Barry Platinum Level Sponsor


    Bill,

    For typical "water cooled" automotive engines being driven moderately, the oil temperature is normally about 15 - 20 degrees F. higher than the coolant temperature. Under near continuous full throttle conditions, the difference might be 40 - 50 degrees F. unless there is a substantial oil cooling system (e.g.; an air-to-oil or water-to-oil cooler with thermostatic control).

    180 F. coolant temperature + ~20 F. = ~ 200 F. oil temperature which is not hot enough to get rid of moisture contamination in the oil.
     
    Last edited: May 11, 2019
  12. Bill Blue

    Bill Blue Platinum Level Sponsor

    So maybe there is a need for an oil cooler on an Alpine?
     
  13. Bill Blue

    Bill Blue Platinum Level Sponsor

    How hot does the oil have to be to drive off moisture? Why won't 200 F. do it, is there some sort of molecular attraction, perhaps with some the additives?
    Bill
     
  14. Barry

    Barry Platinum Level Sponsor

    Water turns into a vapor at about 212 F., so something a little higher than that. The OEM engineers pretty much agree that 220 - 240 F. in the sump is a good range. As has been noted, modern oils can handle that temperature with no problem. One reason that modern cars either don't have water temperature gauges (or the gauges don't have numbers) is that modern engines run HOT all the time. Coolant temperatures are typically about 210 F., oil temperatures are typically about 230 F. and the under-hood air temperatures are typically about 300 F. Modern engines typically have plenty of cooling capacity (both water and oil) and the temperatures don't change much between idling / cruising / running hard.
     
  15. 65beam

    65beam Platinum Level Sponsor

    Barry,
    You've listed several valid points concerning temps and other things that occur under the hood but you're leaving out the most important part concerning engines and engine oils. That's the people in the labs of the additive package companies that know, understand and use all this info concerning engines and they develop additives to counter these problems and keep the engines running under severe conditions. The whole thing boils down to a highly refined base stock with high tech additives that allow the oils to do the job required of protecting the engine.
     
  16. Mike O'D

    Mike O'D Gold Level Sponsor

    Water will be evaporating pretty rapidly at 200 degrees, or 180 for that matter. Does it really need to boil in the oil to get rid of it?
     
  17. Barry

    Barry Platinum Level Sponsor



    Mike,

    The answer to that question depends on whether you want to eliminate some of the water or all of the water from the oil. Evaporation is an equilibrium process and depending on the atmospheric conditions, some water will evaporate at any temperature between freezing and boiling. OTBE, the higher the temperature the higher the rate of evaporation, but evaporation will never get rid of all the water in the oil; doing that requires an oil temperature in the sump high enough to boil the water. Boiling the water out of the oil is only part of the process; the other part is removing the water vapor from the crankcase (typically via a PCV system).

    My previous posts were responses to specific questions and related to modern engines which run hot all the time. Series Alpine engines are not modern and I am not suggesting that they should consistently operate with a coolant temperature of 210 F. and an oil temperature of 230 F. Doing that would require coolant and oil systems that can maintain those temperatures under all operating conditions (idle / cruising / running hard / full throttle). Like most 50+ year old cars, stock or near stock Series Alpines do not have that capability.

    One solution is to frequently run the car hard / hot enough to get rid of the water in the oil, but not hot enough to adversely affect the engine or the oil. That is something which I would not attempt without having known accurate gauges for oil pressure, oil temperature and coolant temperature and being confident about the mechanical condition of the car. The other solution (older than Series Alpines) is frequent oil changes to temporarily get rid of the water and living with relatively short engine life.
     
  18. 65beam

    65beam Platinum Level Sponsor

    Barry made a very good comment Use a current spec oil and use the three or three rule. That means you change your oil every three thousand miles or every three months and use an oil with a current API spec. The additive companies and the oil companies have formulated blends to protect against problems of the past and present .
     
  19. Mike O'D

    Mike O'D Gold Level Sponsor

    Thanks for the responses guys - good information. At some point when I have some time (who knows when that will be) I'll modify a spare oil drain plug with a thermocouple probe and see what temperature the oil is actually running.

    Mike
     

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