oil pressure issue
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Freshman User
Joined: Jun 2008
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From: Goldsmith, IN
oil pressure issue
i just rebuilt a 390FE (disassembled, cleaned, replaced all gaskets and seals, reassembled). i finally got it running well. oil pressure was excellent at first, but after idling for about 15-20 minutes, my oil pressure dropped extremely low. the oil level is perfect, and when i had the engine apart, i scraped and vacuumed all oil passages as well as i could. i also installed a high-flow performance oil pump.
any ideas on what could be causing such an issue? could the pump be becoming un-primed? i have no clue whats going on. any help would be greatly appreciated.
any ideas on what could be causing such an issue? could the pump be becoming un-primed? i have no clue whats going on. any help would be greatly appreciated.
Elder User
Joined: Jan 2009
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From: Western N.C.
I'm interested in an answer to this too, as my 360 does something similar. When I first start it, the oil pressure is 3/4 of the way toward the "H" but once it has been driven a few miles, the needle drops to 1/4 at idle. It might have something to do with the viscosity of the oil thinning out once it is heated (been in the teens and twenties here lately), but I don't think it should take that long. I left it idling for 10 minutes in the yard before I went to work, and the needle did not move from 3/4. Once I got to work...4 miles, straight shot, no lights 
...the idle pressure was just below 1/4.
I hadn't really noticed it before I changed the oil filter. From Motorcraft to Fram...could this have something to do with it?
...the idle pressure was just below 1/4. I hadn't really noticed it before I changed the oil filter. From Motorcraft to Fram...could this have something to do with it?
Hotshot
Joined: Feb 2009
Posts: 10,410
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From: Plankinton, SD
If you are relying on the original guage your sending unit is probably bad. You need to put a mechanical guage on it to be sure. That is what happened to mine. Oil pressure showed real good and then when warmed up dropped to nothing.
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Freshman User
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From: Goldsmith, IN
pressure sender was replaced about a year ago. i think im gonna replace it again just in case, but when the sender when bad before, the gauge didnt work at all. now it seems to actually be doing something.
i'll post an update after replacing the sender.
i'll post an update after replacing the sender.
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Freshman User
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From: Goldsmith, IN
mechanical gauge? is that the technical term for an aftermarket gauge that you run a small oil line to?
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From: Duncan B.C.
Yes. That is the type. Get a half decent one. There are cheap offshore ones around but I don't think you can trust them much more than the electric ones.
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What specifically do you mean by "hi-flow" oil pump?
High Volume or High Pressure? If you indeed installed a high volume (HV) pump you'll need to install restrictors in the cylinder head oil passages, otherwise at a sustained speed (think highway) all the oil will pump up into the valve covers.
Usually you just unbolt the rocker shafts and drop an 80 Holley jet in there then bolt back together.
High Volume or High Pressure? If you indeed installed a high volume (HV) pump you'll need to install restrictors in the cylinder head oil passages, otherwise at a sustained speed (think highway) all the oil will pump up into the valve covers.
Usually you just unbolt the rocker shafts and drop an 80 Holley jet in there then bolt back together.
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Freshman User
Joined: Jun 2008
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From: Goldsmith, IN
What specifically do you mean by "hi-flow" oil pump?
High Volume or High Pressure? If you indeed installed a high volume (HV) pump you'll need to install restrictors in the cylinder head oil passages, otherwise at a sustained speed (think highway) all the oil will pump up into the valve covers.
Usually you just unbolt the rocker shafts and drop an 80 Holley jet in there then bolt back together.
High Volume or High Pressure? If you indeed installed a high volume (HV) pump you'll need to install restrictors in the cylinder head oil passages, otherwise at a sustained speed (think highway) all the oil will pump up into the valve covers.
Usually you just unbolt the rocker shafts and drop an 80 Holley jet in there then bolt back together.
also, what is a good source for the Holley 80 jet that you mentioned?
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Not sure where you live, but around here at some Checker Autos, Advance and even NAPA have a small selection of speed parts, including Holley jets and such. So, there should be no need to order from Jegs or Summit.
I am not saying your problem is 100% the oil pumping up into the valve covers, but with that oil pump you should definately consider restricting the oil up top.
Josh
I am not saying your problem is 100% the oil pumping up into the valve covers, but with that oil pump you should definately consider restricting the oil up top.
Josh
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Freshman User
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From: Goldsmith, IN
Not sure where you live, but around here at some Checker Autos, Advance and even NAPA have a small selection of speed parts, including Holley jets and such. So, there should be no need to order from Jegs or Summit.
I am not saying your problem is 100% the oil pumping up into the valve covers, but with that oil pump you should definately consider restricting the oil up top.
Josh
I am not saying your problem is 100% the oil pumping up into the valve covers, but with that oil pump you should definately consider restricting the oil up top.
Josh
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Actually restricting the oil to the heads (specifically the valvetrain) increases the oil available to the crank and rods. The standard FE engine (360/390/428) is referred to as a TOP OILER. The oil goes from the pump to the lifters and then branches to the crank and the branch goes to the heads. Restrict the oil to the heads and you'll get more oil to the cam and crank.
The 406/ 1st Gen 427 was a Center Oiler. The cam and crank had priority over the heads. The Next gen 427 was called the Side Oiler, Crank had priority over the cam and heads.
I usually install 60 Holley jets in my engine builds, but then again I have roller rockers, lightweight valves, viton valves seals etc. A normal engine is around the 80 or 90 Holley jet.
Josh
The 406/ 1st Gen 427 was a Center Oiler. The cam and crank had priority over the heads. The Next gen 427 was called the Side Oiler, Crank had priority over the cam and heads.
I usually install 60 Holley jets in my engine builds, but then again I have roller rockers, lightweight valves, viton valves seals etc. A normal engine is around the 80 or 90 Holley jet.
Josh