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Thread: What's acceptable oil pressure? A little long

  1. #1
    Senior Member
    Join Date
    Feb 2009
    Posts
    4,169
    I've been trying to fire up the 390 in the Stevens and have been fighting little stuff. Here's where I am now.
    On Saturday, I finshed assembling everything and was prepping the engine to fire it and break it in. Before cranking it, I spun the oil pump and no pressure registered on the gauge. I removed the filter, and spun it and tons of oil came out. I removed the filter adapter and checked the gallery to the top end and there was no restriction.
    Today, I pulled the rocker shafts and spun the pump. A decent flow of oil came out the restrictors in the heads, but no pressure to speak of. Bolted down the rockers and figured I'd remove the electric gauge sender and replace it with a mechanical gauge. Only thing around was a fuel pressure gauge, but it goes to 15 psi, so on it went. I spun the pump and got 14.5 psi at the filter. Now, I have no way of knowing how fast the drill motor I'm using to spin the pump is, but I would guess around 4-500 rpm.
    This is a fresh motor, never fired. I'm walking away from this for the night, but I'm wondering. How much pressure should I see spinning the pump with a drill motor? I've done this on the 460's and seen more pressure, but am I just being paranoid?

  2. #2
    lilrick
    if you're only spinning the pump to 500 rpms and you're getting 14 #'s my guess is that it would be more than that when it's really running. Ideally it should have 20#'s at idle and 10 #'s of pressure for every 1K rpm you turn.

  3. #3
    058
    You should have at least 45-50 lbs or more with a drill. If I can't get at least 40-45 with a socket and speed handle cranking by hand there is something wrong. Are you sure all the plugs are in the engine? An FE has alot of plugs and passenger car blocks are most if not all press in plugs. Spinning the pump with a drill motor should bog the motor down so much the drill will begin to heat up. I've used a 1/2" drive gear reduction drill and it will bog too if everything is right.

  4. #4
    Senior Member
    Join Date
    Feb 2009
    Posts
    4,169
    It bogs down and gets hot. I can only check 2 of the plugs with the engine assembled (left lifter gallery next to cam, and front diagonal intersecting the gallery from the o/f housing). The past couple days I've been leaning toward a missing plug (woulda sworn I checked them all), but today getting 14 PSI bothers me. I find it hard to believe I could get 14 pounds with a missing plug. I suppose it could be a soft relief valve in the pump too, but that's getting even harder to believe. The drill could be turning slower, but how much of a difference would that make? I need a beer...

  5. #5
    GofastRacer
    I remember popping one of those press in plugs in a 390 once while priming it and the pressure went to nothing, so i would guess it's in the pump??.. Needless to say that was the last time I ever used those press plugs, I tore it back down and put pipe plugs in!..

  6. #6
    Senior Member
    Join Date
    Feb 2009
    Posts
    1,105
    I think that I would try an oil pressure guage that goes to eighty or so not fifteen and know exactly what I had before I tore it down...
    Steve

  7. #7
    wsuwrhr
    I agree, on all counts, it is a gearrotor pump, pretty much a positive displacement. If it is turning, it is making pressure. When you fire up the drill, it will load the drill down major once it primes.
    I am not a Ford expert, are you missing a galley plug or something?
    Brian
    You should have at least 45-50 lbs or more with a drill. If I can't get at least 40-45 with a socket and speed handle cranking by hand there is something wrong. Are you sure all the plugs are in the engine? An FE has alot of plugs and passenger car blocks are most if not all press in plugs. Spinning the pump with a drill motor should bog the motor down so much the drill will begin to heat up. I've used a 1/2" drive gear reduction drill and it will bog too if everything is right.

  8. #8
    wsuwrhr
    Good advise.
    As shitty as it sounds Roost, you are so deep into this project prolly should hoist the motor out and take the pan back off for a second look.
    Pipe plugs are your friend.
    Brian
    I remember popping one of those press in plugs in a 390 once while priming it and the pressure went to nothing, so i would guess it's in the pump??.. Needless to say that was the last time I ever used those press plugs, I tore it back down and put pipe plugs in!..

  9. #9
    GofastRacer
    I agree, on all counts, it is a gearrotor pump, pretty much a positive displacement. If it is turning, it is making pressure. When you fire up the drill, it will load the drill down major once it primes.
    I am not a Ford expert, are you missing a galley plug or something?
    Brian
    But they are like the rest of them, they have a pressure relief valve!..

  10. #10
    GofastRacer
    Good advise.
    As shitty as it sounds Roost, you are so deep into this project prolly should hoist the motor out and take the pan back off for a second look.
    Pipe plugs are your friend.
    Brian
    After that experience, it don't matter what motor it is if it has press plugs, they are replaced with pipe plugs!..

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