oil pressure

[speedy44]

hello, me and a friend built an engine and the oil pressure drops to practically nothing once it warms up. i can't figure it out yet. i'm curious about the rocker arm shafts, as far as the directions of the oil holes. do they go above the shaft bolts or below. i installed them above with the reasoning that this would get the oil to the top of the pushrods once the shafts fill up. but does this allow oil to shoot out thru the top of the rocker arm and not maintain pressure throughout the engine. when it's cold it'll register 45-50psi easily. but as it warms up it drops to 10 or less by a mechanical gauge. it does increase rapidly with rpm's though. all suggestions are welcome and greatly appreciated. i couldn't find any pictures on the rockershafts to help me out when we put it together. thanks

[craftsman]

Did you check the bearings for oil clearence? Did you change cam bearings? Give a little more info on the build.

[knightfire83]

Replace the oil pump? Was this a complete tear down and rebuild? What size engine was it?

I once had a Pontiac engine do the same thing as yours. I went to replace the timing chain, and used a wire wheel in a drill to remove the old gasket material on the block. Seems some wires broke off the wheel and eventually made their way into the oil pump. Found a piece of wire jamming open the pressure relief valve on the pump, thus low oil pressure. Installed a replacement pump as the old one also had a worn cover plate and oil psi was good as new.



And from a crane cam Ford rocker shaft install guide:

"When installing the rocker shaft, the small oil-feed holes on either side of the stud mounting holes must be facing down towards the cylinder head to provide proper lubrication to the rocker arms"

Seems your oil holes are facing the wrong direction.

[speedy44]

this is a 390, complete rebuild all new bearings & rings, oil pump, etc... the rocker shafts have been a big question to us. i just don't understand why the pressure decreases as it warms up. we will try to switch the shafts over the next couple of days and i'll keep progress posted. thanks and by the way, how can i find this "oil pressure" blog easily when i bring up the web site? i'm new to all this forum stuff and don't really know much about the how's, do's, & dont's. thanks again!

[knightfire83]

Oil psi normally goes down because as the oil heats up, it thins out and flows easier. Engine parts made of different metals also expand at different rates when heated and create slightly bigger oil clearances.

I wouldn't think the rocker shafts would create your problem, but I'm not sure, other possible problems could be:
- Bad oil psi gauge
- Wrong size bearings / worn bearing surfaces / bearing oil feed hole oriented incorrectly
- Gouge or nick in the bearing surface (especially cam bearings)
- Oil pump relief valve stuck open / worn gears or cover plate
- Plugged oil pickup / pickup tube gasket missing / or pinhole in the pickup tube (sucking air)
- Wrong oil viscosity
- Incorrect idle speed
- Plugged oil passages
- Missing oil pump mounting gasket
- Loose oil pump mounting
- Leaking or missing oil gallery plugs behind the timing gear or at the rear of the engine.

None the less, here's a post about the rocker shafts you may enjoy reading: http://www.fordification.com/forum/view ... re#p426897

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