Oil pumps: High velocity, high pressure, both, neither?

I have always used high volume pumps without a problem.
In order to suck the four quarts out of the oil pan your end clearance would have to be very tight and your oil drain back holes plugged. The oil is delivered to the crank where it leaks back to the sump. Oil is delivered to the cam bearings and lifters where it drips back into the pan. Only the oil that goes up the pushrods take oil into the heads and most of that oil runs back along the outside of the pushrods back to the pan. There are two 1/2" return holes that each will flow more volume than all the pushrods on each head can to carry oil back to the valley where slots and holes drip oil back on the cam to keep the lobes lubricated. Most of the oil that the pump pushes runs right out of the relief valve because there simply isn't enough flow to the engine for it to go into the engine. The relief valve dumps most of the oil right back into the pan.
What will clear your pan of oil is the rotating mass of crank and rods. Oil can cling to the parts and load up on them until there isn't enough left in the pan to lubricate the engine. The faster the engine turns the more oil clings to that rotating assembly. To keep the oil off the crank and in the pan where it is needed you can use either a windage tray or a scraper. The fastest turning engines use a scraper and multiple pumps to scape the oil off the rotating assembly and then suck it away from the crank and into a dry sump tank. For engines that don't turn fast enogh to need a dry sump system a windage tray will keep the oil off the rotating crank assembly and in the pan where it does the most good.
If you need proof of this use a pre-oiling pump drive with a high speed 1/2 inch air drill to turn your pump while the engine is on a stand and try to fill the heads. There is simply not enough oil flowing to the heads to drain the sump. Remember that your oil pump turns at 1/2 the speed of your crank so if you turn it at 3000 rpm it is pumping the oil just as it would to have your engine running at 6000 rpm. You will see that there is a lot more oil running out of the relief valve that you are getting to the head. You will also see that there is no build up of oil in the heads. It drains away faster than it is being pumped into the heads.

 

And now, THIS old guy knows why one of the freeze plugs blew out on my 'last' break down and caused me to lose oil pressure. Sad part is, I went through a lot of anguish and paid an "expert" a lot of money to find the problem and fix it. On the down-side, HE wasn't the one to find the problem. On the upside, he didn't charge me for labor after he pulled the engine, put in new bearings, new lifters, etc., etc. and put it back together. If he would've looked behind the timing sprocket, he'd have noticed that one of the freeze plugs was missing (like my brother did when he diagnosed the problem a few days later.

He also couldn't explain the "funny metal/lead-like pieces" in the oil pan.

Another lesson learned.

 

Another vote for a standard pump. The only time you need additional volume capacity from the pump is if you increase the volume need of the engine. A good "for instance" is oil squirters that spray down the bottom side of the piston.

HP pumps are only needed for high speed engines, and even then unless it's an oval track engine it's not really needed. The reason is that you need additional pressure to keep the wrist pin lubed. In other really high HP applications, you can squeeze all the oil out between the bearings and the journals because the forces are so high. I haven't really seen that either, but in theory it could happen. Even considering both of these times when additional pressure would help, it's only necessary in a durability type engine. For a drag engine or a street engine, that only sees these high speeds and loads every once in a while or is rebuilt often it's not an issue.

A deep sump pan that will hold another 2 or 3 quarts with a good baffling and windage system is something that every engine could benefit from. Oil coolers, or even a finned block of aluminum attached to the pan are also beneficial to all engines.

As long as the oil pressure gauge reads more than 30 at idle and about 60 at higher speeds, you're good to go.

 

I have a Melling HP/HV pump with a deep sump pan in my '73. If you decide to go this route, you might consider tapping and installing screw in oil galley plugs. The tap in style can blow out with HP pumps - even when you create a retainer detent.

 

Nope...too much work. I will just stick with the standard pump with a hardened shaft (Anna is a work...no giggling this time)

 

I always use the high volume pump in my race motors. I never use the high pressure ones. Motors don't need a lot of pressure, it just washes out the bearings. But in my race motors I've always felt better knowing that a high volume of oil was available. And I've used Mellings forever, (30 years anyway) only had one problem. And that was an old pump where the pressure valve stuck and dumped all the pressure at idle. Moral of the story...always use a new pump whenever you rebuild a motor.

 

Couldn't say it any better than this,just me and ATOs opinion.