Ask Away! with Jeff Smith: Should I Run a High Pressure/High Volume Oil Pump in My Street/Strip 383 SBC Stroker Engine?

I’m building a 383ci small block Chevy for my 1980 Malibu that will see a combination of street use with some fun runs at the drag strip. I don’t plan on running nitrous or supercharging. At least not yet. My plan includes a set of 195cc Dart Pro 1 cylinder heads and 10:1 compression but I’m going to have to stick to my budget with a mechanical flat tappet cam matched with a big single plane intake and a 750 cfm Holley mechanical secondary carburetor.

My buddies tell me I should run a high pressure and high volume oil pump to make sure I have plenty of oil pressure when I rev it beyond 5,000 rpm. But I’ve also heard that this isn’t really necessary. So I’m not sure which way to go. Do you have any recommendations?

G.S.

This is a great question that leads right into a common oil pressure urban myth. The short answer to your question is that unless you plan on spinning this engine upwards of 8,000 rpm or pushing power up to or beyond 800 hp, there really isn’t any need for anything more than a standard pressure and standard volume oil pump.

In fact there are plenty of good reasons to avoid high volume/high pressure pumps for mild street engines.

For close to 70 years now, the small block Chevy has been racking up untold millions of street miles without the need for excessive oil pressure or volume. Having said that, why then are there multiple companies selling high performance oil pumps on the pressure and volume side? This has as much to do with internal engine clearances as with anything else.

If you drastically increase the main and rod bearing clearances, this will require more oil pump volume to fill that space and a thicker viscosity oil.

But assuming you keep your rod and main clearances around 0.0025 inch or tighter, a stock oil pump is more than capable of supplying a sufficient volume of oil to maintain pressure.

Remember that pressure is created when the pump’s capacity exceeds the volume requirement to feed the engine. When the pressure created by the pump reaches a given point, the pressure relief valve in the pump will open and bleed enough pressure off to maintain the pressure set by this relief valve. In most oil pumps, this relief valve is a simple needle valve seated by small coil spring rated to compress at a given pressure. With a small block Chevy this is generally around 55 to 60 psi. This maximum pressure is more than enough to force oil throughout the entire engine and thoroughly supply lube throughout.

Idle oil pressure is another area where many hot rodders think that they must have 30 psi or more for a bare minimum. This is another fallacy that seems to gain new life every few years. If you think about it, oil pressure is merely a representation of resistance to the flow of oil throughout the engine. Since the oil pump is spinning at half engine speed because it is driven by the camshaft, idle oil pressure will be lower. But any oil pressure above 10 to 20 psi is more than enough to supply oil to the rotating parts.

Think about it: An engine at idle is only putting out enough power to rotate itself and perhaps drive the pump on an automatic transmission. Neither of these demand much power. Since there is no excessive load, there’s no need for excessive pressure. So 20 psi is more than enough pressure at idle to feed the engine and keep it properly lubricated.

Plus, the old adage of 10 psi per 1,000 rpm is also outdated. With proper clearances and because the quality of engine oil is so good these days—especially the synthetics—50 psi is sufficient.

We had an experience several years ago when our 560 hp 421ci small block at an open road race broke the end off of the oil pump pickup due to vibration and the oil pressure fluctuated to between 45 to 50 psi at maximum power at 6,000 rpm and a subsequent look at the rod and main bearings revealed no damage—they looked nearly new.

So the point is that for a street small block Chevy, oil pressure beyond 60 psi is just wasting hp. There are certainly exceptions, but as a general rule you are safe with this.

There’s far more to this discussion than we have space to give this, but ultimately if you run quality performance engine oil in your street engine with 50 to 60 psi of oil pressure, your engine will be fine. But you don’t need to invest in an expensive high volume, high pressure pump to achieve this. There are more important places to invest your money, like a high quality oil pan to ensure that there is always oil around the pump pickup. That’s far more important than a high pressure pump.