Oil pump testing

Discussion in 'Small Block Tech' started by UNDERDOG350, Oct 5, 2019.

  1. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    I learned several interesting things with the bench testing of my rebuilt oil pump/front covers I though I should share with everyone. Some of my findings go against what we've been told by others and believed to be true but actual testing does not support. Use this information at your own risk. Civil discussions are welcome if there is any data to support your point.

    First, before test observations are listed lets talk about oil pressure. As I've said many times and some guys are starting to understand, your oil pressure gauge only tells you if the pump is working. The number it displays can be manipulated to show whatever you would like to see. Oil volume to the bearings is what keeps your engine alive.
    In a perfect world you only need enough oil to keep a film between the bearing and the journal. Any more is just deadheading and making a higher number on your gauge. Also consuming HP. That being said you need a reserve to compensate for wear over time and thinning due to heat. Think of it like a hydraulic lifter. It compensates for valvetrain wear so you don't have to adjust the lash. The reserve of oil (pressure) is there so you won't have to increase the oil as bearings wear or temp increases.
    When I say you can manipulate the pressure gauge this is something that has been suggested in several posts. Add STP or 20-50 to increase the reading. If this higher reading puts your mind at ease then it has some value to your psyche but not your engine.
    When time permits I intend to test the same pump apples to apples with several weights of oil to see what effect it has on the gauge.

    OK now to the observations. For background info see my post "Re man timing cover with oil pump"
    We generally accept the need to enlarge the oil pickup passages in the block and use a larger pickup tube. In my tests I have seen where the OE size 350 pickup provides more oil than can be used. There was never a time where the pickup was starving the pump for oil. Granted I can not simulate 6000RPM however the oil passages supplying the bearings and lifters never change size with RPM either. You can only force so much oil through the engine and the restrictions (bearing clearance) are a fixed size. This makes me question the old 10PSI per 1000RPM that is universally accepted as a standard. Required reading, see my post " Oil pressure concern #412" where I drove 2400 miles at speeds up to 100mph with never more than 20PSI oil pressure without damage.

    My test fixture has a screw in plug similar to a carb jet. I use this to simulate the restriction of an engine to provide a reading on the gauge. I wanted to see what it would do with the output completely plugged. There was no oil movement into or out of my mock oil pan as expected. It appeared the oil was opening the pressure relief and simply recirculating through the oil pump. It was working the drill quite hard and produced 67 PSI max at the RPM the drill could provide. I found this interesting. When the relief opens that is the point it is drawing the highest volume thru the pickup. Was the pickup tube causing restriction? Answer is no. The point is if the pump was getting all the oil it needed why would I need or want to use a larger pickup or drill the block for more flow? The only time this would be necessary is it you raised the relief opening point higher than 60PSI. How high? Don't know, that's for the nerds with the slide rules to determine. I run my engines to 6000 often and never use more than the 60PSI spring in the OE relief valve. Side note for cars that sit without being started for weeks at a time. It takes longer for the pump to draw oil thru the larger oil pickup tube and drilled out block galley increasing the time that bearings are running dry. Use an oil filter with the best anti drain back valve you can find to help with this. I use Purolator One PL25288. It's smaller size also fills faster. I've heard that Bosch ST3423 is also good but have not tested it yet.

    Next I found it odd when I tested the first cover with a new oil filter it took several minutes of run time to remove all the air from it. It was pumping foam the whole time. I believe it just took time to saturate the filter media. I used this same filter on the second cover and after the filter filled there was no more air. This tells me when doing an oil change first pour some oil into the filter for the media to soak up before installing it. Then don't rev the engine for several minutes, just let it idle to prevent bearing wear.

    If anyone has something they would like me to try with this setup let me know.
    Dano, rjm, Julian and 1 other person like this.
  2. Mart

    Mart Gold level member

    Interesting Steve. I agree with possibly not needing super duper enlarged block passages, as you said, the bearing holes are the restriction anyway.

    Smoothing and blending corners on block, timing cover and oil pump seem very helpful.

    What about a remote oil filter setup to keep filter upright & full? Would get oil to bearings immediately when starting.

    Keep up the good work!:)
    Julian likes this.
  3. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    Remote filter might stay full but would need to pump thru longer hoses. Might be a wash.
    Would be nice if TA incorporated the pump onto the front of the crank like the last V6's had.
    On my BB Chevy I always fill the filter with oil before screwing it onto the engine.
    300sbb_overkill and Julian like this.
  4. Mart

    Mart Gold level member

    I was thinking maybe a custom 90 degree elbow / conversion connection off the existing filter location on cover. No long hoses.
  5. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    That would work. I thought some vehicles with V6's had that. Maybe boats.
  6. Quick Buick

    Quick Buick Arlington Wa

  7. MrSony

    MrSony Well-Known Member

    Always thought of adapting a GN oil cooler to a 350.
    Julian likes this.
  8. Mark Demko

    Mark Demko Well-Known Member

    Don't need to adapt a GN cooler, they sell 'em, I had a Derale on my '75 455 Electra, BUT I towed a 24 'Sea Ray ('bout 55oo lbs)
    The engine was under load quite bit, which heats oil.
    For just a driver, its not worth the expense, and extra plumbing, and risks of leaking.
    On the GN's I believe it was intended more as an oil warmer, seeing as it goes thru the radiator.
    MrSony likes this.
  9. Mark Demko

    Mark Demko Well-Known Member

    Always wondered why the OEMS ran the pump off the cam (half crank speed) instead of full speed off the crank.
    If you think about it, theres really no advantage, other than packaging.
    Running at half crank rpm, we can achieve excessive pressure, running AT crank rpm, ( twice as fast now) I'd think you'd have to bypass A LOT of oil, or reduce the size of the gears.
  10. Jim Nichols

    Jim Nichols Well-Known Member

    80's 4.1 Cadillac V6 had the swivel filter mount. D&D used to sell them. The Ford swivel mount will work if you make a custom piece to thread to the Buick and use a Ford filter. Rover V8s can use the Ford part as it has the same threads.
  11. 87GN_70GS

    87GN_70GS Well-Known Member

    The 10 psi per 1k rpm rule of thumb was used to overcome centrifugal force. The rod bearings are fed from passages in the mains. On a spinning crank, oil is being slung outward from the main bearing surface. The pump has to overcome that force to pump oil from the main surface towards the center of the spinnjng crank then to the rods to feed them.
  12. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    Following up with more results.
    Today I completed cover #3. Clearance came in at .002". Testing with the same 10w30 I've been using produced 54 PSI on the test stand. FYI this number is NOT the maximum it can produce, just what is making at the RPM my drill is twisting the pump using the orifice (restriction) sized to simulate an engine attached.
    I then switched to Valvoline VR1 20w50. This oil made 47PSI. However this lower number may be due to the fact that the drill was running at lower RPM attempting to move the thicker oil.
    Next I put in 0w20 synthetic Mobil one. With this oil it was turning to foam when reaching the drills max speed. It did make 55PSI but it might have done more if it were solid oil. I don't know how it was finding air to make foam. The pickup was completely submerged the entire time. I would let it sit for the air to release from the oil and try it again with the same result. It would hit a certain speed and start blowing foam. For this reason I've decided not to try 0w-anything in my 72.
    Keep in mind these tests were with the oil at 65 degrees. What would happen at 200?

    As for enlarging the pickup galley and pickup. Remember, oil does not compress. If you have a 1/2" hole feeding the front cam bearing and main galley, using a larger pickup galley will not make a difference. You can only move so much oil out no matter the size of the pickup. The oil has to go somewhere. If you are showing pressure on the gauge you are NOT taxing the pickup. The flow is not one to one.
    MrSony and Mart like this.
  13. Mark Demko

    Mark Demko Well-Known Member

    Interesting ;)
  14. Mart

    Mart Gold level member

    I agree. My oil pressure is slightly higher on this eng compared to last build. I used the same exact cover/pump without taking it apart. I believe higher pressures are because of tighter bearing clearances, not from the enlarged block passages.

    Like you said Steve, lazy river. If you had 1" block passages the pressure wouldn't go up any. The stock oil pump gears can only move a certain amount of oil.
    MrSony likes this.
  15. MrSony

    MrSony Well-Known Member

    Ever test the 3423 filter?
  16. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    Have not tested it on the stand. Was going to put it on the car to see if the drainback feature works as well as the Purolator.
    Did you suspect it would effect oil pressure?
  17. MrSony

    MrSony Well-Known Member

    It's quite possible. I doubt it, but it's a possibility. It is a restriction in the system. Albeit a very necessary one. There's a trade off on flow vs filtration. Too bad you can't test a filters ability to filter. You could shift the whole filter market lol.
  18. Jim Blackwood

    Jim Blackwood Well-Known Member

    The 300 had a suction passage that may have been as small as 7/16" diameter. On the later V6 engines Buick saw fit to enlarge the suction passage to 5/8". Buick had the resources to do a much better job of testing than you do Steve, just a simple fact. So I'm going with what they did. That GN engine was quite the performance piece of hardware and if it needed that much oil I'm sure a V8 is going to need just as much if not more. I drill to 9/16" as that strikes a nice balance between flow capacity and the risk of break-outs. 5/8" is probably not necessary if proper bearing clearances are maintained, though for a very high performance engine I wouldn't be in a position to say. The system has to be in balance. If you run massive clearances like a SBC you will need much more flow which means bigger gears and more flow into the pump. Thicker oil does a better job of maintaining a film in larger clearances because as metal approaches metal the actual contact point is smaller. Also your end clearance in your pump will influence performance with different weight oils because a heavier oil will be slower to flow around the ends of the gear teeth, which will show up more with larger end gaps. You may be getting cavitation with your 0 weight oil at the gear ends. All of this will affect your results, meaning proper testing has to include every variable under every condition. I think what you are doing is a good idea and will provide useful information but the scope is kinda limited. While it is good to question stereotypes, many of those old rules of thumb were developed by trial and error and have a very firm foundation in actual real world testing and are respected for the very good reason that they work in the real world. In short, they have more fact behind them as things now stand than your testing does. That's a fairly significant hurdle to overcome.

  19. Dr. Roger

    Dr. Roger Stock enthusiast

    Any testing with an STP S25 filter?

    I've always heard not to use the higher flow oil pumps for some reason, but not I don't remember why. Maybe they aren't necessary.
  20. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    Wow Jim kind of harsh. As I admitted from the start these are simple tests that would not cover every situation hence the disclaimer use the information at your own risk.
    Also stated Civil discussions are welcome if there is any data to support your point. Your comment "many of those old rules of thumb were developed by trial and error and have a very firm foundation in actual real world testing and are respected for the very good reason that they work in the real world. In short, they have more fact behind them as things now stand than your testing does."
    is not data. And I've already said the same thing.
    Please go back and read the entire first post and you should see what I mean. Or don't.

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