wonso79

Any thoughts on using a Hi Flow or Standard Oil Pump on a 302 engine? What's the advantages and disadvantages?

67mustang302

Spend the money on a hand prepped high pressure pump if it's a performance engine.

Standard pump is ok in most applications. But in high performance stuff there are better options, and the oil pump can determine whether the engine lives or dies.

High volume will generate more pressure sooner (trying to flow more volume through the same resistance), so the engine will actually be able to handle more load at lower rpm without damaging the bearings (more flow at lower rpm), but will cap out pressure like a standard pump at higher rpms. Once it gets to the set pressure, usually about 65psi, the bypass opens and it functions like a normal pump.

High pressure pumps are basically a standard pump, but with a higher pressure setting in the relief valve. You won't notice a difference except at higher rpm...instead of hitting a pressure ceiling at around 60-65psi, it'll top out at around 85psi. This means more oil gets to the bearings at higher rpm than with a standard, since the relief won't open to bypass oil until higher in the pressure range (and therefore rpm range).

A hand prepped high pressure pump will have much tighter internal tolerances than a typical pump, so with less leakdown they generate more pressure sooner (like a high volume), and since the relief is set higher, they flow more oil at higher rpm since the bypass doesn't open as soon. They're a much more efficient pump internally.

Hand prepped high pressure pumps tend to run around $100+ though.

wonso79

Thanks for that information, makes tons of sense! I found a high flow oil pump on CJPonyParts for around $70 bucks, might have to pick it up!

67mustang302

Standard street blueprinted? That's about the price for the standard hand prepped. The race ones with better parts are more expensive, over $100 like I said.

What is the car being used for? The oiling system is critical to get right, if you invest in a good pump, invest in a good pan.

I run the Canton 9qt diamond shaped trap door baffle road race pan one mine, with the built in scraper and a girdle mounted windage tray. I'd have to roll the car on it's ****in side before the pump can't get oil.

wonso79

Weekend driver, leaving it stock except going to upgrade to a 4v carb and intake and maybe a performance cam.

67mustang302

Might as well just use a standard pump from Melling then. No point really in spending more money than needed.

scootchu

Correct me if I'm wrong but more isn't always better. Seems to me I remember hearing stories of high volume pumps emptying a standard pan, which kinda defeats the purpose of a well oiled engine. Again I may be wrong.

Iskwezm

also dont forget about the oil pump shaft.A "stock" type shaft can twist when used with a high volume/pressure pump.

67mustang302

You shouldn't use a stock shaft when rebuilding an engine anyway. The standard Melling shaft is usually fine, but the ARP is prudent in performance engines.

And a high volume pump emptying the pan is a myth. It comes from people's anecdotal stories from the internet, and the pump/pan manufacturers (Melling, Canton etc) even have literature on the use of high volume pumps that say a hv pump won't drain a pan. If the oil pan gets emptied it's a bearing clearance or pan size issue or oil return issue, or a mix. A high volume pump isn't able to pump any more oil than the bearing clearances will allow for a given pressure. Since a std pressure hv pump doesn't flow any more oil at high rpm once you get to the pressure ceiling of 65psi (same pressure, same resistance, therefore the same flow), if a hv pump will empty a pan, so will a standard pump. The hv will flow more oil at lower rpm where it builds more pressure sooner, but flow at that point is still well below maximum.

A high volume and high pressure pump could drain a pan since it has a higher pressure ceiling and more volume, but at that point you have a high performance/race engine and if you're running a stock pan then you're stupid.

They've actually found that the biggest issue in pans getting drained is oil return from the top end, drain holes in the heads/block that restrict flow back to the pan. Clearance is another one, where the extra oil gets thrown out of the loose bearings faster, and before it all drains back the pan empties. But in the case, you already had low local bearing pressure before the pan went dry and were already causing bearing damage.

Just an FYI, but the oil pressure we measure is general system pressure in mainline flow, the actual pressure in the bearing at the oil wedge that's supporting the crank is many orders of magnitude higher (because of some physics that's going on involving motion). Typical wedge pressures at the bearing are in the thousands of psi of pressure, with eccentricity causing running clearances to measure in ten thousandths of inches.

wonso79

thanks guys, I'll just go with a standard pump.