[Bad Karma]

I see alot of bad press on High volume oil pumps. Is it true they suck the pan dry and cause bearing failures on street engines? Is High pressure better? For a strong steet motor what is the best choice?

[Bad Karma]

OK guys feel free to chime in with what you run atleast.

[pro-tour79]

hi presure and hi volume are nothing more than marketing terms when it comes to pontiacs, the "hi presure" ones are nothing more than RAIV 60 PSI pumps and there are no hi volume pumps on the market for Pontiacs other than the Titan

[TR]

The more you think it through, the more curious you get. I just don't see how you can have both a high volume, and a high pressure pump. Can anyone explain? I'm confused.

Pump moves X amount of fluid...in this case oil.

Forcing fluid volume through small clearances would raise pressure.

So:

For increased pressure we would need to either;

1) Put out more pump volume

or

2) Decrease bearing clearances

I just don't see any other way.

[JSchmitz]

The max. pressure (provided you have adequate volume) is set by the pumps internal bypass. More specifically the internal bypass spring. Wider bearing clearances do require more volume at a given rpm to provide the same pressure. I believe, for most applications, Pontiacs have an adequate pump volume from the factory. They don't turn the super high rpm's like some makes. The general rule of thumb is 10# per 1000 rpm. Pressure is a measure of resisstance to flow. As you have basically stated. You just left out the bypass part of the equation.

[engineer]

Pontiacs never had a high pressure oil system. Pontiacs were always a high volume system. yes, they had pumps up to 60 psig but compared to a high pressure system like a chevy has, pontiac is not high pressure. my chevy runs 40-50 psi at a stop light compared to the pontiac at 20-30 and then as rpm increases, so does the pressure. Just like Pontiacs never had big and small blocks, they never had a high pressure and low volume systems. why do you think they had 7 quart oil systems if they did not move high volumes? you can get by with less oil pan capacity if it was run at high pressure.

[Bad Karma]

Thanks for the responses I guess for ponchos hi volume is the way to go.

[Tom McQueen]

Nope. Pontiac has never had a hi VOLUME oil pump. Every Pontiac oil pump has the same gears in it. Same length and same number of teeth. Its the physical size of the gear (length) and number of teeth (diameter) that determines the volume of oil the pump moves per revolution. However, this generic sized pump came with 3 different pressure relief springs. The standard (~45#), the hi-po pump (~60#) and the RAV/SD pump (~80#). So Pontiacs do have a hi-pressure pump, but not a hi volume pump. If you want a hi-volume pump you must look to the aftermarket (Titan).

[P@blo]

Nice information Jschmitz....i have by accident reved my 400 past 6000 RPM a few time but were only short bursts.....Will this excceed the oil pump capacty or was your 10# per 1000RPM a general giude line assuming the different main sizes of Pontiac motors (smaller main will have less inerta).......Let me know please

[Jack Gifford]

Just a reminder, that going drysump allows you to choose from a variety of pump displacements.

[engineer]

those three springs were not available in the same pump housing. Melling made the pumps for pontiac and the housing differed for the 80 psig pump which was not offered in a 60 or 45 range. if you want high pressure, look at chevy systems. pontiac was still low pressure. look at the bearing clearances and flow path and you can see it was for more flow, not pressure.

[JSchmitz]

I believe that general rule of thumb came from none other than Smokey Unick. If my memory serves correct (or was it Bill "grumpy" Jenkins?). Although, I'm beginning to think it serves less correct every day.

Seriously, it's just that; a general rule. There's no switch that goes off and blows your engine up. If it makes you feel better, my 455 has seen 6-grand more times than I care to admit. That was when I was younger, and wilder. Different main sizes do require different pressure per rpm to maintain the gap between journal and bearing. I have a chart somewhere that plots it for Pontiacs. I think it's in the "Pontiac Engine Design and Blueprint" book. I think that's the title. There are many engineering types on here that can give a better explanation of the effect journal bearing diameter has on oil pressure requirements.

[theoldone]

Originally Posted by Burn out Buster

I see alot of bad press on High volume oil pumps. Is it true they suck the pan dry and cause bearing failures on street engines? Is High pressure better? For a strong steet motor what is the best choice?

I run the SD455 pump w/80 psi spring. It has 90 psi cold at idle, then after it warms up it drops to 30 psi at idle 900 rpm in gear- but instantly goes back up to 80 when revved or driving. At cruising speed 2000-2600 rpm is has 60 psi.

If you look into what other engine makes run, you'll find they all run lots of oil pressure- in the Ford 390-427-428 engines, they come right out and say, if you have less than 60 psi oil pressure, shut the engine off or the bearing with be gone.

Oil pressure won't hurt your engine- lack of it will. If you run a high pressure pump 80 psi, just be sure to restrict oil passages to lifters if running a solid flat tappet or solid roller cam. Hydraulic lifters are self-limiting.

[pro-tour79]

sorry I forgot about the 80 psi SD pump in my post

[theoldone]

The RA IV 60 psi will do the job in most cases- but I'd rather have the added insurance of the 80 psi on high rpm 428-455 big journal blocks over 6000 rpm.

[Jack Ferris]

engineer-I have both the 60 psi pump(RA4) and the 80(SD) psi pumps. Both have different springs but use the same exact housing and rotors. In fact I swapped springs around in my 80 PSI pump with the spring from my 60 to lower the pressure. The only pumps I've seen that have a different housings are the factory units that had a smaller hole for the pick up tube.

[Robert C.]

High pressure is the only way to go. You need to have 10 lbs. for every thousand rpms. Because of the large dia. crank journels the high pressure works best. You need to feed the bearings and cool them with oil. In this day in time the poor pump gas that is out there will make your motor knock and beat the bearings to death. The best is high pressure to combat this problem or run race gas mix.

[Tom Vaught]

Quote:

"Pontiacs never had a high pressure oil system. Pontiacs were always a high volume system. yes, they had pumps up to 60 psig but compared to a high pressure system like a chevy has, pontiac is not high pressure. my chevy runs 40-50 psi at a stop light compared to the pontiac at 20-30 and then as rpm increases, so does the pressure. Just like Pontiacs never had big and small blocks, they never had a high pressure and low volume systems. why do you think they had 7 quart oil systems if they did not move high volumes? you can get by with less oil pan capacity if it was run at high pressure."

First off we need a little more history here:

Pontiac's traditional engine did indeed come with two different volume pumps. A normal volume and a higher volume pump but it was many years ago. Early 287/316-317/347/370 type engines were built with a oil pump that had a smaller id inlet tube and screen. This provided a given volume. Later engines that everyone on the board knows about 326/350/389/400/421/428/455 and larger used the HIGH Volume oil pump/ inlet tube with the larger diameter inlet.

So there was a Normal Volume and High Volume option at one time. There was also a pick-up tube that followed the oil in the pan too.

As far as pressure goes. All of the pumps as was mentioned have the same length and diameter gears. If you bought a typical oil pump in the 60s you might get two different springs as the stock 389 engines received the 40 psi pumps. (My GTO had one). The HP engines came through with a different spring for the by-pass and would run 60 psi. Prior to that deal we would stack several oil pump covers from old oil pumps together and put a spring spacer in the by-pass circuit to push the pressure up. The longer better designed spring was a better deal. So after a while all Pontiac pumps had a THICK COVER and a longer high pressure (60 psi) and 40 psi spring in the replacement pumps. They copied the hot rodders!

With the introduction of the 455 SD engines the Pontiac enthusiast saw the 80 psi spring pump appear with the longer spring housing.

Pontiac was having issues on the dyno trying to pass the durability tests and one of the cheap fixes was substituting the 60 psi spring and spring cover nut for a much longer 80 psi spring ($2.50) and a longer spring cover ($3.50). The dealers/ pontiac were charging a high premium for an oil pump (had the 455 SD name) for a oil pump with $6.00 worth of real cost difference. That pump is now called the M54F oil pump. The 60 psi Pump goes by M54D or M54 DS (Screen included).

The M54F pump was needed due to the fact Pontiac was trying to run high rpm with a long stroke crankshaft for more than a few seconds. The higher pressure pump overcame more of the centrifugal forces inside the crankshaft and fed the bearings better. Some people tried cross drilling too to fix the issue. Most very high rpm engines do not use the cross-drilling today as the oil passage causes reduced oil film/ bearing surface area where you need it. Better to have ONE
shear film of oil going a longer distance than to have two smaller oil shear films turning one and off. JMO.

Tom V.

ps I think all of you guys are close to the answer. You need
adequate pressure to establish the oil shear film, adequate bearing clearances to remove the oil from the crank/ bearings to remove HEAT. You need a proper by-pass to remove load on the oil pumping system at lower rpm. You need an oil
pump with a proper inlet tube size to prevent cavatation of the pump at higher rpm, and you need a proper screen/ oil pan to make sure the pump gets continous oil.

[Bad Karma]

Thanks again everyone for this great discussion. I hope this helps others besides myself when building thier next poncho power mill.

[Jack Gifford]

Tom V- Since you said "... a little history is needed ...", I'll nit-pick a little with your wording about the early pickup "following the oil in the pan", only because some readers might think it was a desirable feature. The floating pickup was pivoted to allow vertical movement. Its only intent was to float above any crud that accumulated on the bottom of the pan.