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Discussion Starter #1
Yesterday morning when I cranked my truck to go to work my oil pressure didnt even come up, until I started driving down the road at 45 MPH or more then it went back up to normal. When I stop at a stop light my pressure drops very fast to 0 psi. I have been racking my brain as to what it is. If it was the oil pump I would think it would have no oil pressure at anytime. The only other thing I can think of is a spun main bering. Can anyone tell me some signs of this. My motor is a 390 and has about 70k miles on it. If it is a spun main is their anything I can do to get my oil pressure back up?
 

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If you have spun a bearing you will hear a loud knocking noise followed shortly by a rod through the side of the block.I had it happen 3 times on 390s
 

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haha..had a 352 that did the same thing. No noises for about 50 miles or so, then just a slight kind of a squeaking noise from the bottom end, then a louder knocking noise, then ka-boom, and it just stopped. It was a good engine, but they dont like to run with no oil pressure!
 

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Discussion Starter #4
Whatever my problem was, it seems to have disapeared. my oil pressure is now at or slightly below normal all the time. I did buy another gauge to cheack and it was at about 5 psi.
hopefully what ever the problem was it wont happen agin.
 

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Possibly the pressure relif valve in the pump is sticking or hanging slightly open. This would cause very low pressure at idle but could be OK at higher RPMs. If it does it again, it would be a good idea to replace the pump.
 

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Well now back to the question at hand I had the same or similar problem with my 351W.I did a rebuild you know,new bearings and now all is well.Possibly there is a bearing clearance problem.I've been told to much clearance and you get low oil pressure. Does that sound right to you guys?
 

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Yes your bearing clearance has a great deal to do with your oil pressure.Think of the oil being pumped from the pump and then the oil being squeezed through between the crank and bearings,the tighter the clearance the more pressure it takes to push the oil through.Its kinda like running waterout of your garden hose with nothing on the end and then putting your thumb over most of the hole,big difference in pressure right.The weird thing is how the pressure went away and then came back,if it was excess bearing clearance the pressure shouldn't have come back as once the clearance is there,its there until its rebuilt
 

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I have had a few 390s in galaxies,have blown up one or two, check your pickup tube and screen on pump.also make sure pan is clean and windage tray are in place.And to the young FE man chill out. they are a good old boat anchor.The good FEs are the cross bolt main 406 -427 and the 428 SCJ.The 390 H.P.is not a bad engine.But don't freak out on us now.
 
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