400 oil pressure?
Cargo Master
Joined: May 2003
Posts: 2,561
Likes: 1
From: Earth
Interestingly enough, I've read in this forum of guys having really low oil pressure for years and never have a problem. 5 psi is pretty low though, yet 20 isn't that bad for this engine, from what I've read. I know a common fix is to put a heavier weight oil in. How many miles are on the engine?
Cargo Master
Joined: May 2003
Posts: 2,561
Likes: 1
From: Earth
I about freaked out on my rebuilt 400 when I saw it had 70 psi cold and about 35-40 hot with my HV pump, at idle. I don't have problems with the engine, I'm just glad I installed a chromoly oil pump drive shaft. The interesting thing is, when that engine is warmed up and running down the road, you can watch the oil gauge run up and down pretty quick depending on the engine rpm. I've never seen anything like it. I'm running Ford SVO gauges, which I believe are made by auto meter.
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Fleet Owner
Joined: Jan 2004
Posts: 26,007
Likes: 575
From: Brentwood,CA
when the cam bearings were installed was the first one turned to block off some oil flow? that is common and wise to help maintain pressure.
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Laughing Gas
Joined: Aug 2004
Posts: 964
Likes: 1
From: Roseburg, OR
I also have a set of cheapie gauges and my fresh 400 hits just a tick under 70 psi when at cold fast idle and while driving in the first few minutes, then when its warm it's around 50 while running, and dips down just a little to around 35 or 40 at hot idle. Mine acts exactly the same way as 53fatfndr describes.
Postmaster
Joined: Aug 2001
Posts: 4,270
Likes: 5
From: Delaware
The oil presure sensor is located at the back of the motor. The pump is located at the front of the motor. You are reading the pressure after all the main bearings and the passenger's side lifters have gotten oil. The only thing left to lubricate is the driver's side lifters and valve train. If the valve train on the driver's side doesn't tap at idle, then you have enough oil.
If you want to read higher pressure put your gauge sender in the oil gallery port in the front of the motor, near the pump.
There is a kit available to divert oil from the front oil port to the rear oil port (sensor location). I don't think that this is necessary, unless the valves tap, and then I think that this diversion path should be restricted to prevent robbing the front bearings.
The best fix is to turn the front cam bearing or to use oil restrictors in the cam bearing galleries.
New User
Joined: Nov 2005
Posts: 22
Likes: 0
From: florida
I have 400 with good oil pressure, 70's at startup and 50's when warm. I did have a 351m with very low oil pressure and replaced crank bearings(from under the truck) and it helped a little. When I moved the oil sending unit to the front driverside of the block it raise it about 5-10 psi. I didnt do that on my 400.
Cargo Master
Joined: May 2003
Posts: 2,561
Likes: 1
From: Earth
Originally Posted by busted knuckle
i bled the line to the gauge again and now she reads right around 40psi im happy know thanks guys
Elder User
Joined: Dec 2002
Posts: 639
Likes: 0
From: not mass
the port by the oil filter is derectly off the pump so if the pump is good it will look good but the port in the back will tell if there is anything wrong with the motor
so using the front port you can lose all the pressure out of the #3 main and it won't show up on the guage
you can install a external oil line from the port in the front to the rear port this will equlizes the pressure and you dont have to tear the motor apart
well this will not fix the problem but replacing the main and rods will help and short of a good rebuild or HV pump its all that can be done
so using the front port you can lose all the pressure out of the #3 main and it won't show up on the guage
you can install a external oil line from the port in the front to the rear port this will equlizes the pressure and you dont have to tear the motor apart
well this will not fix the problem but replacing the main and rods will help and short of a good rebuild or HV pump its all that can be done