Low Oil Pressure on a 350 Chevy
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    I'm a grown up member now ! Dooby's Avatar
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    Low Oil Pressure on a 350 Chevy

    I have a 350 Chevy Tbi V8 in an 88 Chevy K5 Blazer. Recently changed the oil and I've now noticed my oil pressure reads 0...! I used to have 15w40 but I put 10w30 in. I've read that lighter oils can cause bad oil pressure... Anyone know if this is a possibility??

    The other option I think may be the oil pressure sender has gone bad, or something's been disconnected when I recently had a transmission rebuild.

    Also has anyone got experience with the Halfords Classic Car Oil, think its 20w50.

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    I'm a grown up member now !
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    hi in my opinion valvoline racing mineral oil is the best money can buy

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    Administrator blackpopracing's Avatar
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    Sounds like the wire has been disconnected from the oil pressure sender.
    The sender is at the top rear of the block just behind the end of the inlet manifold to the right of the distributor. Look for a loose spade connector wire which will go on the spade terminal of the sender.
    To check your gauge touch the spade on the end of the wire to the block with the ignition on for a few seconds, this should read max oil pressure on the gauge.

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    Rods 'n' Sods Junkie
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    Had very similar problem several years ago on a G20 with a 350. Random OP dropping to zero after a change. Turned out to be crack in the plastic base of the sender unit - worth addting in a Tee piece and a pressure gauge to get a better idea of real condition of motor. Not an expensive solution as I recall. I swapped out mains & BEBs with engine in situ for reassurance.

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    Off the Xmas card list kapri's Avatar
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    Yup, lighter oils lose you oil pressure, many years ago ( while young and naive ) I swapped 10/40 into an old Hillman Minx engine used to 20/50 . It cost me 10lb pressure throughout the range.

    On the other side of the coin once added STP to 20/50 in a tuned Beetle lump . Gave me 10psi more but made the engine run 10C hotter a soil didn't flow as well .Beetles are air AND oil cooled

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    Rods 'n' Sods Junkie boblester40's Avatar
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    What was you pressure before hand , As capri said you may loose some of the pressure with a lighter oil but if you have gone from say 20-30 on idle cold to 0 then it will be a sender or gauge problem , rig up a manual gauge to the sender port to check

    rgds
    bob

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    Did you change the filter as well,,, if so what brand

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    I'm a grown up member now ! Dooby's Avatar
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    It used to sit about halfway (so 30psi). I think it's too much if a coincidence I only noticed after I had the transmission rebuilt, so possibly pulled a spade connector off. I think I'll probably put some 15w40 back in for piece of mind.

    I did replace the filter yes, I used a Fram Suregrip one.

    Also, I thought the pressure sender on the Tbi motor was located just above the oil filter??

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    Rods 'n' Sods Junkie
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    Do yourself a favour and dump the fram,, also known as the orange box of death,,worst filter you could get hold off...use moroso or wix

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    Administrator blackpopracing's Avatar
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    Quote Originally Posted by Dooby View Post

    Also, I thought the pressure sender on the Tbi motor was located just above the oil filter??
    Ah, yes, sorry I was talking about Gen 1 SBC you are probably correct.

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