Oil pressure

[SBSerpent]

What is 'normal' oil pressure on a stroked 392 Ford Racing motor (430HP). This is the motor on my 2011 build (#983)?
I just changed the oil (9 qts of 10W-30), added two bottles of the zinc additive and using the WIX 51515 filter (5" long filter). While warming up and at idle, the guage was reading 3 1/2 bar (~50 psi). I have seen lower readings at idle after driving the car around for awhile. Just wondering what are the parameters that cause the oil pressure to rise and fall....and what is considered 'normal' at idle and at higher revs.

[hauss]

sounds about right my 351 stroked motor runs the same pressure as yours.

[genolan]

My Roush 427 running 10w30 is about 3 1/2 bars during warm up but drops to 1 3/4 Bars when fully warm on a hot day at idle, Roush recommends 10w30 as long as PSI remains above 20 at idle.

[Ozzie Goat]

do you have an oil cooler with thermostat ?

Mine is 3.5 bars warming up, thermo closed.
Around 2-bar with the thermo open.

[bobcowan]

Originally Posted by SBSerpent

Just wondering what are the parameters that cause the oil pressure to rise and fall....and what is considered 'normal' at idle and at higher revs.

In broad terms:

The maximum pressure is somewhat controlled by the spring in the oil pump. The valve opens when the max pressure is reached, and oil is diverted back to the oil pan. A high pressure pump usually just has a stiffer or shimmed relief spring.

If bearing clearances are tight, pressures tend to be higher. Think of putting your thumb over the end of a garden hose. Bearing clearances tend to increase as the surrounding metal gets hot. When bearing clearances increase, pressure drops a bit.

Higher viscosity oil will increase pressure to a point. Going from 30-40 probably won't change anything. But going from a 30 to a 60 probably would.

The old adage is 15-20 psi at idle, and add 10psi for 1,000 rpm's doesn't really work all that well with modern technology. 15-20 at hot idle is good. But max pressure for most engines should be 45'ish.

It takes energy to create pressure. The more energy you use to spin the motor around, the less energy reaches the tires.

The drive mechanism is off the front of the cam, and through the distributer gear. Work that mechanism too hard and it will eventually break.

There is no need ever for a high pressure pump on a Ford Windsor engine. There's a lot of debate about high volume pumps, though.

You need enough oil viscosity to maintain proper pressure, and no more. If your street engine maintains good pressure with 0W-20 oil, there is no advantage to using 5w-40. Race engines can see improved valve train stability with a 40 oil.

[SBSerpent]

No oil cooler.

Does the brand or size of oil filter affect pressure?

[eschaider]

This is an age old question that has more urban legend and mystery surrounding it than Big Foot does. The phenomena of fluid pressure (including oil pressure) is very old science and actually quite straight forward.

With a known unregulated fluid volume supply (hydraulic pump) and an orifice you can determine the changes in pressure by simply by changing the orifice and / or the volume of the fluid supply.

The pressure rises or falls as the square of the change in orifice area. Lets use Bobs garden hose example because it is a very good illustration. If our spigot is capable of delivering, lets say 10 gallons per minute, and we have a nozzle diameter of 1 square unit of area measure (pick your favorite units square millimeters, centimeters, inches etc.) reducing that area by one half will increase the pressure by a factor of 4 compared to what it originally was.

Fluid flow and pressure have a similar relationship. To double the flow at the nozzle the pressure at the nozzle will rise by a factor of 4 compared to what it originally was. Similarly if we maintain the same fluid pressure at the nozzle and double the area, the flow will become 4x what it was. So far seems like pretty straight forward common sense other than the math

When we include a pressure relief valve it gives the fluid system designer the ability to tailor the low speed pump delivery or the high speed pump delivery. Additionally the block and head castings grow as their temperature increases. The difference in bearing clearances between cold and operating temperature will amount to a whisker over 0.0005" (a half thousandth) of an inch in an aluminum engine, less in cast iron. That additional clearance will increase flow and reduce pressure unless your oil pump is undersized.

Lets say you want to increase low speed oil flow but have a maximum higher speed engine flow you do not want to exceed. This is where pump capacity and the pressure relief valve comes into play.

By going to a higher volume pump you will increase oil flow to the engine bearing surfaces at all engine speeds but most importantly at low speed where you were most interested in increasing flow. The rub comes in as engine speed increases.

By doubling the engine speed and therefore the pump speed, you will quadruple your high speed oil pressure. But I only wanted 60 psi oil pressure at 5000 rpm and unregulated the bigger pump will produce over 200 psi at 5000 rpm. This is where the pressure regulator, what we call the pressure relief, comes into play.

By using a pressure regulator with adequate flow capacity to bleed off unneeded volume and setting the pressure relief opening at 60 psi we can have the increased low speed flow and also limit the 5000 rpm (or wherever you pick) pressure and flow to our preferred 60 psi target.

That's it in a nut shell. Here is an excellent 2 minute video from Melling where George Richmond shows the effect of changing nozzle size by changing bearing clearances. Click here => Melling Video

If you are using an OHC engine (like I do) something you need to be aware of is that, your cams are at the end of the oiling food chain and get oiled last. Because an oil system is a controlled leak, putting additional clearance at the rods and mains will take oil away from the cams and put you at risk of seizing a cam in it's saddles, breaking your timing chains and using up a lot of expensive parts.

Even if you have an OHV engine design you still have to oil the heads for rocker trunions and valve spring cooling. If you reduce the oil to the heads you are cheating the rockers, pushrods and springs. At some point in time, probably sooner rather than later, you will have to pay the piper — and it will not be cheap.

Originally Posted by SBSerpent

What is 'normal' oil pressure on a stroked 392 Ford Racing motor (430HP). This is the motor on my 2011 build (#983)?

Stroker cranks do not change the engine's oil appetite, it remains the same as the stock stroke version of the engine.

Originally Posted by SBSerpent

I just changed the oil (9 qts of 10W-30), added two bottles of the zinc additive and using the WIX 51515 filter (5" long filter). While warming up and at idle, the guage was reading 3 1/2 bar (~50 psi).

Warm up pressure and operating pressures will always be different no matter the oil you use. The important pressure you want to pay attention to is the pressure at normal operating temperature and as Bob already stated heavier weight (higher viscosity) oils will produce slightly higher oil pressures.

Originally Posted by SBSerpent

I have seen lower readings at idle after driving the car around for awhile. Just wondering what are the parameters that cause the oil pressure to rise and fall....and what is considered 'normal' at idle and at higher revs.

As oil temperature comes up to engine operating temperature, oil viscosity will decrease. Absent changes in volume, increased temperature reduces viscosity and at constant volume it will also reduce oil pressure. Additionally, as the engine comes up to operating temperature the block and heads will increase in size because of the increase in temperature.

This increase in engine temperature to normal operating temperature will add about a half thousandth (0.0005") to the bearing clearances because of casting growth attributable to the temperature increase. The effect of the increased bearing clearance will be a reduction in oil pressure unless the oil pump has adequate reserve capacity to make up for the new found oil clearance.



Ed

[bobcowan]

Originally Posted by SBSerpent

No oil cooler.

Does the brand or size of oil filter affect pressure?

Yes. In a Windsor engine, the oil goes from the pump directly to the filter. The stock oil pressure sender is after that.

A cheap (Fram), clogged, or too small filter can be restrictive. The pump is pushing against the restriction, and that increases the pressure enough to open the relief valve. Everything after the filter then has a lower pressure, and a lower flow.

I prefer either the Motorcraft FL1-A or a Purolater Pro-1 filters.

[SBSerpent]

That being said, is it best to always go with a longer (higher capacity) filter than a shorter (lower capacity) filter?

[cycleguy55]

Originally Posted by SBSerpent

That being said, is it best to always go with a longer (higher capacity) filter than a shorter (lower capacity) filter?

A higher capacity filter is capable of filtering more contaminants before its internal pressure relief valve opens and oil bypasses the filtering media. So, yes, generally a longer filter is preferred to a shorter filter - all else being equal.

BTW, Wix 51515 is a good filter, equivalent to Motorcraft FL-1A IMO.

[SBSerpent]

Yes, the 51515 is what I am using. I had swapped out to the WIX 51068, which is almost an inch shorter in length but then figured I didn't need to because the 51515 fits between the motor and frame no problem.

[patrickt]

If you're worried about low oil pressure then you should buy an FE. With FEs, there's no such thing as low oil pressure. See: Oil Temp 265 Degrees and Pressure Only 9 PSI -- Did Ford Say That Was OK for a 427?

[Lou1119]

Originally Posted by bobcowan

Yes. In a Windsor engine, the oil goes from the pump directly to the filter. The stock oil pressure sender is after that.

A cheap (Fram), clogged, or too small filter can be restrictive. The pump is pushing against the restriction, and that increases the pressure enough to open the relief valve. Everything after the filter then has a lower pressure, and a lower flow.

I prefer either the Motorcraft FL1-A or a Purolater Pro-1 filters.

I installed an Oberg oil filter setup on my Roush 427. Better flow increased pressure and is cleanable. These are the same filters used on NASCAR machines , NHRA fuel dragsters. More expensive but they are reusable as long as you own the engine. Check it out a Oberg Industries

[Lou1119]

Originally Posted by Lou1119

I installed an Oberg oil filter setup on my Roush 427. Better flow increased pressure and is cleanable. These are the same filters used on NASCAR machines , NHRA fuel dragsters. More expensive but they are reusable as long as you own the engine. Check it out a Oberg Industries

It is not Oberg industries. Look up Oberg oil filters.

[cycleguy55]

Oberg Filters has been manufacturing eco-friendly filters, filter accessories and race parts in Washington State since the early 80’s. Originally designed for auto racing, our filters exceptional filtering and diagnostic capabilities were quickly recognized and are now used in many applications including: marine, agriculture and industrial.

https://www.obergfilters.com/

[SBSerpent]

Where on the motor and exactly how is the oil pressure measured on a 351W?

[spdbrake]

Originally Posted by SBSerpent

What is 'normal' oil pressure on a stroked 392 Ford Racing motor (430HP). This is the motor on my 2011 build (#983)?
I just changed the oil (9 qts of 10W-30), added two bottles of the zinc additive and using the WIX 51515 filter (5" long filter). While warming up and at idle, the guage was reading 3 1/2 bar (~50 psi). I have seen lower readings at idle after driving the car around for awhile. Just wondering what are the parameters that cause the oil pressure to rise and fall....and what is considered 'normal' at idle and at higher revs.

My 408W runs at 40psi @idle once up to temp and being driven a bit. You should be fine. I used to see 70 on cold start up before I added a thermostat to the oil cooler. Now is a around 60psi. The Thermostat I use has a 10% bypass so the oil cooler oil slowly gets up to temp and you don't dump a slug of cold oil into the engine once the Thermo opens. I run VR-1 10-30 oil.
The Ford Racing 392 installation notes to use a synthetic or reg 20-50W oil. Since its a roller lifter motor you don't need the Zinc additive.
https://performanceparts.ford.com/do...7-A392D392.pdf

[bobcowan]

Originally Posted by SBSerpent

Where on the motor and exactly how is the oil pressure measured on a 351W?

Just behind the fuel pump boss there's a 1/8" NPT hole in the block.

[cycleguy55]

Originally Posted by spdbrake

My 408W runs at 40psi @idle once up to temp and being driven a bit. You should be fine. I used to see 70 on cold start up before I added a thermostat to the oil cooler. Now is a around 60psi. The Thermostat I use has a 10% bypass so the oil cooler oil slowly gets up to temp and you don't dump a slug of cold oil into the engine once the Thermo opens. I run VR-1 10-30 oil.
The Ford Racing 392 installation notes to use a synthetic or reg 20-50W oil. Since its a roller lifter motor you don't need the Zinc additive.
https://performanceparts.ford.com/do...7-A392D392.pdf

Agreed. Straight out of the linked document:

INSTALLATION INSTRUCTIONS:

Engine Prep:

2. The engine has been hot tested. The 20W50 factory fill oil should be changed after the break-in cycle. Any good quality natural or synthetic 20W50 oil may be used.

I'd skip the zinc additive and run a good synthetic 20W50, per instructions. That will raise cold and hot pressures, and may also reduce engine temperatures. I know my engine runs a bit cooler on synthetic oil than it does on dino, presumably due to reduced internal friction.

P.S. If it were my engine I might even consider 10W50 synthetic.

[Blackbart]

Is it necessary to "bleed" the oil line from the oil filter (FE Engine) to the oil pressure gauge to remove air trapped in the line? It would seem to me that oil and air compress at different levels and if there is air in the line the gauge may not read true oil pressure.