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Atlas oil pressure

Discussion in 'Other Norton Motorcycles' started by Gilesy, Mar 21, 2019.

  1. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    I have a 1962 Atlas. The engine has been re built, crank re grind/new shells, re bore with new pistons and rings, new valve seats and guides etc, also new 6 start oil pump from Andover Norton, it has the original low pressure feed to the head. I have also fitted a Holland Norton works anti sump valve and oil pressure gauge. I don't want this to be about the rights and wrongs of anti sump valves, I accept and understand both sides of the argument. However, my concern is this. On starting from cold I get a reading of around 65psi which with 30 of reasonably hard riding minutes drops right back to 10-15psi, even at 3-4000 revs. It has Duckhams 40 mono grade oil in it.
    Any ideas? Should I even worry? My Commando has had the same treatment and maintains 30-40psi at higher revs when hot.
     
  2. dynodave

    dynodave

    Joined:
    May 28, 2003
    If you run the same 40W oil, then I would look to put a thermocouple just before the engine, in the oil feed line, .
    Atlas and commando oil tank and system plumbing are different and all things being equal the oil temp "should" be the same therefore the pressure should be close too...
    Not having useful data would make ME worry
     
    Last edited: Mar 21, 2019
  3. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    Sorry, the Commando is running on Castrol classic 20w50. There seems to be plenty of flow on the return in the Atlas, Commando has the early central oil tank. Should I try the Castrol in the Atlas?
     
  4. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    What are the differences between the engines? The oil pump and speed of the pump is different (3 start vs. 6 start, pump housing differs too). Head lubrication is different (if stock), the early Atlas being lubricated from the low pressure hot oil return line which means kind of a droplet lubrication I guess. Plumbing of the Commando is usually at the oil line banjo at the cylinder head, but is there a high pressure outlet on the early Atlas engine?

    -Knut
     
  5. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    Atlas has new 6 start pump and low pressure feed to the head from oil return feed.
     
  6. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    @Gilesy

    I have the same set up as you .... 6 start pump and low pressure feed to the head, in my Atlas. I have a low pressure light, but no oil pressure gauge.

    Back in the early days, 60's and 70's, I ran 50 W oil with an oil cooler. I never had a problem in 85K miles.

    Now I rum modern 20W50 oil without an oil cooler. My low pressure light does not come on or flicker at idle, but I must say I have not run the bike with the low pressure light yet in 100F Texas heat.

    I think DynoDave is on the track ..... your oil is thinning out. Try the Castrol 20W50 and report back on the pressure you get.

    FWIW, oil pressure does not prevent prevent metal to metal contact. Oil film strength, on the order of 100K psi, keeps parts apart, oil pressure merely gets the oil where it needs to be, and a pressure of 10 psi is adequate for that purpose, presuming there are no unusual obstructions to oil flow.

    Slick
     
  7. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    Ok thanks for that, I'll give the Castrol a go. It certainly performed well in Jim Comstock's trials.
    Cheers
     
  8. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    Castrol classic 20w50 gives a slight improvement, I'm now getting 15-20 psi when oil is hot at 3-4000 revs. At idle pressure drops to around 5psi but there is a constant flow of oil from the return. To me low oil pressure has indicated a lack of resistance due to wear in the engine, but everything in this engine has been restored replaced. The new oil pump seems to have made little difference to oil pressure readings. Mystery.
     
  9. kommando

    kommando

    Joined:
    May 7, 2005
    Look at the pressure release valve, maybe it's set low, also look at the pump joints to ensure no leaks and the seal to the timing cover is in good condition and sealing. As TexasSlick says the oil pressure tells you it's getting delivered and staying long enough for the oil wedge to form and so create a gap between bearing and journal, so it's a secondhand detail not a primary one.
     
  10. Triton Thrasher

    Triton Thrasher

    Joined:
    Feb 10, 2009
    Do you know what your big end bearing clearance measures at?
     
  11. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    You might try a shim behind the conical oil seal to ensure it is making a good seal. However, if you are getting 65 psi when cold, I would think both the seal and pressure relief valve are good.

    I have heard the worst thing one can do to a Norton, is put an oil pressure gauge on it. It creates more anxiety than a prostate specific antigen blood test.

    Slick
     
    dynodave likes this.
  12. dynodave

    dynodave

    Joined:
    May 28, 2003
    The actual result is that individuals, that do not have understanding of the thermal effect on liquids, will not understand why the pressure has gone down. Uneducated people sometime have only single dimensional reaction to a two dimension cause and effect.
    Uneducated does not mean stupid, but the "ah ha" moment has yet to happen and hopefully will upon education!
     
  13. mdt-son

    mdt-son

    Joined:
    Jan 19, 2012
    Hi Giles, I am still wondering where you take our pressure readings on the Atlas. For obvious reasons it can't be at the cylinder head. There are a few factors to consider. I believe the Atlas runs hotter than the Commando due to severely overheated oil reaching the timing chest. As this oil is returned straight on top of the oil pump, the latter will be heated more than on the Commando, hence there will be more leakage from the pump. For an indication of what's going on, temperature readings of the timing chest near the oil pump would be very helpful. Such readings can be performed contactless using infrared or laser technology, or you may glue on a termocouple probe.
    You may not be aware of the fact that oilways, oil junction block and pipes were upgraded by AMC in 1965/66 to ensure proper feed of the 6-start pump. Whether this means your oil pump is strangulated, I cannot say.

    IMHO, the oiling system of the Dominator engine should have been redesigned at the same time by routing the hot oil head drain directly to the oil sump rather than to the timing chest. I believe there is sufficient oil leakage from the pump to lubricate the timing chest. If not, providing a tap off the big end lube oilway using a metering jet would be a simple task. It has been shown elsewhere on this site that oil pump pressure increases substantially when timing chest temperatures are lowered. This is a route I plan to explore on my Mk3 engine.

    -Knut
     
  14. texasSlick

    texasSlick VIP MEMBER

    Joined:
    Jan 2, 2013
    If Knut is correct in reply #13, the solution may be the simple addition of an oil cooler.

    Before I ran an oil cooler, i could not rest my hand on the oil tank for more than a few seconds. With a cooler, I could hold my hand on it for as long as I cared to.

    I have since removed the cooler ..... my thinking is modern oils do not require one.

    Gilesy might compare oil temps in the oil tanks of his Atlas and Commando using a simple cooking thermometer. Similar temps in both tanks would indicate overheated oil is not the problem ..... hotter temp in the Atlas tank would support the use of an oil cooler.

    Slick
     
  15. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    Thanks for your replies. The bike had a 6 start pump when I stripped it down, but it had obviously been dismantled before. The oil pressure gauge feed comes off the back of the timing chest where later high pressure feed to head is. I will certainly investigate the thermal effect on liquids, there are a couple of threads on this forum that talk about it. I sort of get it that hot oil is thin and therefore is easier to move around the oil system causing a drop in pressure, it is just how much of a drop is acceptable. I am encouraged by the flow rate on the return. Lacking any sophisticated temperature measuring equipment I will try the thermometer in the oil tank method. I will also check rubber seal on the oil pump. Failing that I might just remove the gauge. I had an old Saab turbo that used to get hot, I just put my cigarette pack in front of the temperature gauge and not worry too much.
     
  16. dynodave

    dynodave

    Joined:
    May 28, 2003
    "IT" pump or engine ?
    Just curious about pump condition...2 brand new AN pumps I have tested as quite healthy. Old pumps have been real bad when stressed by a tight rebuild and two engines did not last the break in period and blew up (not my rebuild work)

    Yours does not sound to be that bad
     
  17. Gilesy

    Gilesy VIP MEMBER

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    Aug 27, 2017
    I meant the engine, not the pump, the pump's a brand new out of the wrapping AN item.
     
  18. Bernhard

    Bernhard

    Joined:
    Apr 20, 2011
    Pre mid- 1966 and post 1966 Atlas engines were different –post 1966 had 6 start oil pump and different oil block with bigger bore holes, bigger holes in crankcase to/from oil pump-it’s all in the official Norton workshop manual. NOTE; if you go by the 6 start/ 1966 oil block with bigger bore holes, bigger holes in crankcase route you are liable to have oil tank draining into the sump problems, like I did.
     
  19. nortonmark

    nortonmark

    Joined:
    Oct 18, 2018
    Oh my gosh folks, put strait 50 weight as instructed by mc manuals, 40 for cold
    norton Mark
    Hot engine lower pressure,cold engine higher pressure, but pressure non the less, no Norton I owned ever broke down from lack of oil pressure, cept those guys who put the check valve in line with oil tank lol
     
  20. Gilesy

    Gilesy VIP MEMBER

    Joined:
    Aug 27, 2017
    OK, I put a new oil pump seal and timing side oil seal in, correct 'squish' when tightening timing case. The OPRV had one shim in, so I added another and the needle went off the dial on cold start so removed both. Start pressure is now 65. I then took bike out for two identical runs, about 20 miles, some traffic some winding A roads and about 6miles of dual carriage way going uphill. Bike was allowed to cool between runs. First run with Castrol classic 20-50 and then with Penrite classic medium 25-70. The temperature in the oil tank was the same for both oils at 155deg F at the end of each run. The pressure with the Castrol remained at 35-50psi until I hit the dual carriage way and went at 4k to 5k revs. Pressure quickly dropped to around 10psi. It recovered to around 15-20psi on the last A road section and was showing 2psi at idle. The Penrite was about the same for the initial roads, maybe fractionally higher, but again dropped on the dual carriage way but only to 18psi. It also recovered to around 20psi and was showing 5psi at idle.
    I think I am happy with the Penrite, most of the riding I will do on this bike is around Devon and Cornwall, avoiding motorways where possible. Was it included in Jim Comstocks oil test?
    Temperatures seem normal from what I've read on this forum, I do run a spin on oil filter which might have some cooling effect I suppose.
    I can't decide whether to put a shim back. I have read a lot on this forum about this but I still don't see that the OPRV does much except on cold start. Will putting a shim back make any difference to running oil pressure? I'm not convinced.
     

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