Oil pumps

Discussion in 'Engine Performance + Maintenance' started by nobears, Apr 7, 2020.

Car Parts
  1. nobears

    nobears I'm Awesome

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    Is a high volume high pressure worth it on these? Namely my 88 4.3 V6. Since I’m doing a very mild overhaul (rings, gaskets, and bearings, no machine work as the cross hatch is good, and journals all look ok and decks are relatively flat) I figured now would be the time while the engine is on the stand. I am looking at potentialy a melting M99HVS.
     
  2. b454rat

    b454rat I'm Awesome

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    Just get a high volume, not pressure.
     
  3. df2x4

    df2x4 Domestics only.

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    Personally I would be hesitant to put anything but a factory oil pump on a 4.3L. They already use the same oil pump as a 350. My red '97 with a Vortec 4.3L will peg the oil pressure gauge at 80PSI on a cold start, and holds 45 at hot idle.
     
    Last edited: Apr 8, 2020
  4. L31MaxExpress

    L31MaxExpress I'm Awesome

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    4.3 does not really have a need for a high volume. I would get a standard volume Vortec pump with a 3/4" inlet and 3/4" pickup tube and a Z/28 Pink 70 psi relief speing.
     
  5. AK49BWL

    AK49BWL GMT400 Forever!

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    Shoot, my 4.3 pegs close to 80 cold and never drops below 50, even hot lol. Rebuilt engine 2 years ago and replaced the pump with a Melling M155 from Napa. It's good enough for my liking, 2 years and 26000 miles later.
     
  6. alpinecrick

    alpinecrick I'm Awesome

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    How much oil pressure is indicated on the gauge is very dependent on the oil filter being used. The difference in oil pressure on my Vortec 5.7’s can show 20+ lbs difference between a synthetic media filter vs my Wix/NAPA Gold conventional filters.
    Synthetic media filters restrict flow with 5-30 or higher weight synthetic oil in those engines. Don’t even think about using conventional oil with synthetic media filters.
    I know some will disagree.......
     
  7. L31MaxExpress

    L31MaxExpress I'm Awesome

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    I am not buying that their is that much difference between filters unless you have a plugged or otherwise non working bypass valve. Same thing for people claiming massive oil pressure gains deleting the oil cooler lines. I have run with and without the oil cooler lines and run standard and synthetic media filters with Mobil One for 6,000+ miles. Never saw a noticeable pressure difference running 5w30. Not saying you did not observe what you observed but I feel that what you are seeing is a problem. I also did not notice a pressure loss after fitting an Amsoil bypass filter although my oil stayed like new for nearly a year and 7,500 miles after it went on.
     
    Last edited: Apr 8, 2020
    stutaeng likes this.
  8. stutaeng

    stutaeng I'm Awesome

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    Wait, a synthetic filter is +20 psi over a conventional? Heck, I didn't even know they made "synthetic" filters. That's the snake oil I've been looking for my truck!

    Last summer I was getting the check gauges light and gauge was negative on my '99 NBS 4.3 Vortec. I had about 5 psi with mechanical guage, so I switched to something like 5W-50 or 10W-50, and got a slight boost. It now has about 8 psi at idle checked with a mechanical gauge. Dash shows about "0" psi.

    These are all idle pressure. It does go up as RPM increases. By buddy keeps arguing with me saying to change the oil pump, but I keep telling him it's the bearing clearances. I'm at 266K miles, so the truck owes me nothing. Recently, I developed an engine oil pan leak, so I will drop the pan to take a look....not really sure what to look for :) Oil pickup tube o ring is the only thing I can think of. Engine "seems" to run fine.

    I'm getting ready to retire the truck from being a daily driver, so not sure if I should just do another junkyard 4.3 or do an 5.3 swap, also from junkyard. Rebuilding the original engine with machine shop rates is going to be too much money. The transmission needs a valve body rebuild too, LOL.
     
  9. 454cid

    454cid Sooper Pooper

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    Reread the post.....
     

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