351C - Oil pump priming - checking pressure and verify operation of bypass spring

[Billy73]

I am priming the oil journals by pulling the distributor out and manually rotating the oil pump drive shaft. All is good with this respect of getting oil to where it is needed, but I am wondering if it is reliable approach to also check proper operation of the oil pump pressure bypass valve/spring?

Getting oil to flow through the lifters only takes about a half dozen rotations and pressure begins to build. For reference, I am using a Melling high volume oil pump, using break-in oil, and the oil is cold (50deg).

I hooked up a mechanical oil pressure gauge at the back of the engine, and I'm observing 100+ psi, with about 1 rev/sec! So, this had me wondering if my oil pump is operating properly. I would expect the bypass spring to keep the pressure from going too high, but maybe a much higher pressure is needed to overcome the inertial resistance of the spring. Another thought is I need to drive it with a electric drill to maintain a constant speed. I'm acquiring another oil pressure gauge to rule out a faulty gauge.

 

[Stanglover]

Personally, I'd NOT be using a Melling high volume oil pump. I see you are a newer member to the forum, so you may not have read about my experience when my engine builder chose to install a h/v pump without asking me. After only a couple of summers running the car, I started having signs something was not right. There was another unrelated issue brewing as well which finally had me take the motor back to be reworked.
What was found was that the h/v pump caused oil to literally blow past the first cam lobes and lifter, destroying the cam and lifter. The debris then went through the mains, taking them out as well. Now, I' no mechanic, but that is what they described the damage as. The motor was rebuilt under warranty, installing a standard volume Melling pump and I've had no problem since and that's been 6 years now and probably 7k miles.
So, unless your motor has been set up to run an h/v pump, please be aware. More is not always better.
As for oil pressure, I use a mechanical gauge as well. It normally runs at around 70-75 psi, dropping to about 45 hot at idle. I'd say 100 is way too high.
Are you turning the pump counter clockwise? I assume you are.

 

[tony-muscle]

When I built my engine I had about 80 psi during priming with a standard Melling pump. Now a couple of years later with the engine running cold I get 80-85 psi max. As Stanglover pointed out, beware of using the h/v pump unless your engine is built for it.

 

[Billy73]

Thanks for the feedback. Yes, counter-clockwise. I hooked up a second gauge, and it's tracking with the other gauge...so not a faulty gauge.

I sent off a query to Melling to find out the bypass relief pressure. I understand these oil pumps have alternate pressure springs that can add +15psi above "standard" relief pressure. I don't have to pull the engine.

 

[Bentworker]

That is a lot of oil pressure. Most folks run a standard pump.

1) The bypass might be faulty. If memory serves me right they are held in by a cotter pin. I top out at 80 psi, but I have a standard pump.

2) I would be worried the oil pump driveshaft shearing or the distributor gear living a hard life.

 

[Cleveland Crush]

I am priming the oil journals by pulling the distributor out and manually rotating the oil pump drive shaft. All is good with this respect of getting oil to where it is needed, but I am wondering if it is reliable approach to also check proper operation of the oil pump pressure bypass valve/spring?

Getting oil to flow through the lifters only takes about a half dozen rotations and pressure begins to build. For reference, I am using a Melling high volume oil pump, using break-in oil, and the oil is cold (50deg).

I hooked up a mechanical oil pressure gauge at the back of the engine, and I'm observing 100+ psi, with about 1 rev/sec! So, this had me wondering if my oil pump is operating properly. I would expect the bypass spring to keep the pressure from going too high, but maybe a much higher pressure is needed to overcome the inertial resistance of the spring. Another thought is I need to drive it with a electric drill to maintain a constant speed. I'm acquiring another oil pressure gauge to rule out a faulty gauge.

What weight break-in oil are you running Billy? Point being with your tight bearing clearances (100 psi=high restriction to oil flow) you may have to run very thin oil to get that pressure down substantially. Current engine design favors volume over pressure in virtually all applications. 40 to 60 running psi with proper volume will cover most all applications. Factory built Clevelands and all the other Ford engines run a long and happy life at 40-50 psi.

 

[351c1971]

Normal oil pressure specification in the factory manual is 45-75 psi a 2000 rpm.

I also have the standard Melling pump and it toped out at 80 psi when primed. With the drill, I could see the pressure rise rapidly and then suddenly stop rising at 80 psi when the bypass opened.

Keep in mind that the distributor turns at half motor rpm, so priming the motor at 1,500 rpm is equal to 3,000 motor rpm.

 

[351c1971]

Also consider using the heavy duty oil pump driveshaft, as this is a known weak point.

 

[Stanglover]

What weight break-in oil are you running Billy? Point being with your tight bearing clearances (100 psi=high restriction to oil flow) you may have to run very thin oil to get that pressure down substantially. Current engine design favors volume over pressure in virtually all applications. 40 to 60 running psi with proper volume will cover most all applications. Factory built Clevelands and all the other Ford engines run a long and happy life at 40-50 psi.

In our cars, the oil gauge, if you had one, only showed high or low, so one had no idea what the actual pressure was. As long as it was towards the high side we "guessed" the pressure was good.

 

[Billy73]

I received a reply back from Melling...

47 psi idle - 80 psi bypass

I had 10w30, then swapped in 5w30...both experienced the same pressure. I ordered one of the oil priming adapters, so I can hookup a drill and try to get to a steady-state reading.

 

[351c1971]

You should hit the bypass right away with the drill. you might need a 1/2" to prime the pump. It takes a lot of torque when the oil is cold. The 47 psi is for hot idle.

Mine was 70psi cold idle and 47psi hot idle when running the motor.

 

[Billy73]

Followup: I drove the pump with an electric drill and it appears the bypass valve is not opening. I held the rpm as closed to fixed as possible (which was not very fast at all, ~2 rev/sec, i.e. 120 rpm (engine 240rpm), and the pressure was holding steady at about 140 psi.

 

[Bentworker]

Followup: I drove the pump with an electric drill and it appears the bypass valve is not opening. I held the rpm as closed to fixed as possible (which was not very fast at all, ~2 rev/sec, i.e. 120 rpm (engine 240rpm), and the pressure was holding steady at about 140 psi.

Time to drop the pan

 

[Billy73]

Dropped the pan the other day (and managed to do it without removing the engine).

For those that are curious, the core plug was installed backwards on the oil pump, so the spring was over-compressed. It was extremely difficult to even manually depress the relief valve, thus the high oil pressure I was experiencing.

The core plug is cup shaped. Proper installation should have the inside of the cup holding the spring. In my case, the core plug was turned around, so the spring was "outside" the cup. This amounts to about an extra 1/4" of compression on the spring.

 

[Stanglover]

Dropped the pan the other day (and managed to do it without removing the engine).

For those that are curious, the core plug was installed backwards on the oil pump, so the spring was over-compressed. It was extremely difficult to even manually depress the relief valve, thus the high oil pressure I was experiencing.

The core plug is cup shaped. Proper installation should have the inside of the cup holding the spring. In my case, the core plug was turned around, so the spring was "outside" the cup. This amounts to about an extra 1/4" of compression on the spring.

Are you still using that HV pump? Now might be an opportunity to swap it for a standard pump.
After what happened to my engine, that would be my call, but then it's not my engine.

 

[Cleveland Crush]

Dropped the pan the other day (and managed to do it without removing the engine).

For those that are curious, the core plug was installed backwards on the oil pump, so the spring was over-compressed. It was extremely difficult to even manually depress the relief valve, thus the high oil pressure I was experiencing.

The core plug is cup shaped. Proper installation should have the inside of the cup holding the spring. In my case, the core plug was turned around, so the spring was "outside" the cup. This amounts to about an extra 1/4" of compression on the spring.

Billy, you're far from the first person to experience a reversed oil pump spring cup! Happy you straightened things out.

 

[Billy73]

@Stanglover As it turns out, I looked in my parts bin, and I must have bought at some point a M84A pump - standard volume and standard pressure. So I'll use that.

 

[Stanglover]

@Stanglover As it turns out, I looked in my parts bin, and I must have bought at some point a M84A pump - standard volume and standard pressure. So I'll use that.

That's the pump I have. I don't think you'll regret it. Check the spring cup eh!