Thoughts on 455 oil pressure drop?

Discussion in 'Street/strip 400/430/455' started by 69 stepchild, Jul 14, 2021.

  1. 69 stepchild

    69 stepchild Well-Known Member

    I’d like some input on my 455’s oil pressure. Background: It’s a 73 block, had the short block honed, new bearings, rings, crank turned .10, heads cleaned up. Told my machinist (who since has passed RIP) to keep all the tolerances tight - as has been mentioned in this forums sticky’s. Had him install the grooved TA bearings and a blueprinted TA oil pump for good measure. According to my oil gauge the engine has 80 psi on cold start and hovers around 40 for the first 10-15 minutes of driving, after that it goes down to about 20 psi when cruising a 2k. At idle is when I get concerned ; hovers around 10psi but lately it’s started to go down to 9ish.
    Also when I’m cruising and give it gas the oil pressure goes down 1-2 psi instead of increasing .
    I recently turned the oil pump spring adjustment in a turn to no avail.
    I’m starting to get a little concerned and I find myself constantly glancing down at the oil pressure gauge when I’m cruising. Am I being paranoid?
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    That definitely sounds low. Is there anyway to get the exact clearances for the Mains and Rods? Was the oil pump set up by the shop, or TA? Did you buy a new timing cover with assembled pump?
     
  3. 69 stepchild

    69 stepchild Well-Known Member

    I bought the assembled timing cover with pump from TA. No way to confirm the bearing clearances other than what I requested when I dropped off the motor to be built. Like I said he has since passed away
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yeah, so the pump should be good. The only thing left is the bearing clearances. Just telling him to keep it tight might not have been enough. Is the valve train making any noise? Are you sure of your pressure gauge?

    When everything is right, the 80 psi at start up is normal. 15-20 psi at idle after the car is driven for 20 minutes or so is also OK, but if you breathe on the gas, it should go to 40-50 psi, and you should have 50+ psi at a cruise. It should go up from there at higher RPM. You want to see 11-12 psi/1000 RPM, so 60+ at 5000 RPM.

    Maybe you might want to take the motor out, get the pan off, and measure some clearances with plastigauge. The only other thing is a leak in one of the galley plugs or a clogged pick up, but both of those things seem very unlikely on a new build. Excessive bearing clearances will bleed off oil pressure, especially at the rear of the block, so whatever you are seeing is lower at the back. Don't run the engine at higher RPM until you figure out what the problem is.
     
    Freakazoid likes this.
  5. 69 stepchild

    69 stepchild Well-Known Member

    Valve train sounds fine. The lack of psi increase with rpm’s is super troubling. Guess I’ll try another pressure gauge and if that doesn’t solve it motor will be coming out.
     
  6. Mark Demko

    Mark Demko Well-Known Member

    Define "cruising"
    35 to 50 mph?
    Highway speeds 60 to 80 mph?
    What rpm are you "cruising" at when this occurs?
     
  7. 69 stepchild

    69 stepchild Well-Known Member

    Cruising at any speed (25-65). The oil pressure NEVER goes over 25psi after its warm. Say I'm driving at 50-55 mph; oil psi on the gauge is around 23 psi, rpms around 2k (Transmission is 200 4r). If I give it the gas, the psi drops to 20 psi from 23. When I let off a bit it goes back to 22-23.
    Recently it has dropped below 10 psi when I'm at a light with the car in gear.
     
  8. Briz

    Briz Founders Club Member

    Same happened to the Riv's 430.. Found the mains had been " Wiped" copper showing on all bearings. a few of the rods as well. Had a contaminate get into the oil.
     
    chrisg likes this.
  9. 69 stepchild

    69 stepchild Well-Known Member

    Briz, was this a recent rebuild? Did you need new cam/ cam bearings ? Any cylinder scoring? Not liking where this thread is heading...
     
  10. sean Buick 76

    sean Buick 76 Buick Nut

    Pull the engine ASAP
     
    qak likes this.
  11. Robs455

    Robs455 Well-Known Member

    Remove the oil filter and cut it open, take the filter element out and "unroll" it. Sounds like your bearing have exessive clearance, do you have this oil drop since day one from your rebuild?
     
  12. 69 stepchild

    69 stepchild Well-Known Member

    This rebuild has probably 1500 -2k miles on it. The oil pressure issue (lack of rise with rpms) seems to have been there from the get go.
     
  13. 69 stepchild

    69 stepchild Well-Known Member

    One more thing and might be unrelated: white smoke from tails(smells like burnt oil) on warm start. Checked coolant, no milkshake in the radiator. Also a small flutter in the vac gauge -pulling about 18 psi at manifold.
     
  14. BrianTrick

    BrianTrick Brian Trick

    Drain oil. If you don’t have a magnetic plug,you can simply place a magnet under the drain hole and let the oil run over it. Yes,a little messy,but it can catch any elements that might be in the oil. Then remove the filter and cut it open to check for debris.
     
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  15. 69 stepchild

    69 stepchild Well-Known Member

    Yep. Will drain and report back.
     
  16. DaWildcat

    DaWildcat Platinum Level Contributor

    Good info from Brian.

    The bearings are nonferrous, so you won't see bearing material with a magnet, FYI.

    Oh, and don't use a hacksaw to open the oil filter, the debris from sawing it open will ruin the inspection. There's actually such a thing as an "oil filter cutter", it's kinda like a big pipe cutter on steroids, using a cutting wheel like a pipe cutter does...won't leave debris from the cutting itself. Maybe take the filter to a shop that has one vs buying one?

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    Devon
     
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  17. 12lives

    12lives Control the controllable, let the rest go

    Maybe I missed it - what oil are you running?
     
  18. 69 stepchild

    69 stepchild Well-Known Member

    10w40 with added zddp
     
  19. Mark Demko

    Mark Demko Well-Known Member

    Something is going away, stop driving it, pull the engine.
     
    69 stepchild likes this.
  20. Briz

    Briz Founders Club Member

    The engine had 20K miles on the rebuild. Always ran great and had good pressure. I did a bone head move while converting the engine over to waterless coolant which resulted in losing a head gasket that allowed the new stuff to mix with the oil. Its oil based so it didnt make a milk shake. Within a hundred miles the oil pressure started doing exactly what you described above. The cam bearings were fine and I reused the rings and pistons as is back in the same holes. Cleaned and flushed every passage. Opened and cleaned the lifters as well. Car had .010 bearings so I just bought a new set and put it all back together. Now its as good as new.
     
    69 stepchild likes this.

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