pressure v volume

[fekbmax]

Id like to hear some input on oil pressure versus volume in a higher rpm race type Fe engine.  What kinda pressures do you guys like to see ? When should you worry about washing the bearings out and over heating. ?  I have always went the volume route and not stressed to much over pressure but id like to hear what you guys think.

[My427stang]

I have built a lot of engines and have never seen damage due to too much oil pressure.  However, that needs 'splainin Lucy...

I have seen 100 psi+ engines and it has never hurt a bearing or any other component.  So honestly I tend to think that's a wives tail on the oil pressures an engine can build causing damage.  However, IMHO big pressures CAN cause issues.  It steals power when you may not need the pressure, it's rough on a Ford style oil pump drive, the reliefs sometimes can't control it in cold weather until it warms up, and most common of all, filters and or filter o-rings can blow at crazy pressures.

I too like volume, but ultimately if the output of a Ford style standard pump can build pressure to whatever the relief is set at, my opinion is that a high volume pump doesn't do much different in function.  In other words, if the smaller geared pump can reach 80 psi, a larger geared pump isn't putting out more volume to the motor, it's just dumping more past the relief. 

To answer the question though, I like to see 20 at idle, just so I feel good, they can idle lower without hurting, then I like to see it come up quick to the 60-65 psi range.

The key though, especially with most FEs with small pans and front sumps, is to know that it stays there.  As an experiment years ago, prompted by a discussion with RJP, I put a 1/4 copper tube on my 427 feeding a larger gauge, at launch on street tires, the gauge wiggled (really dropped toward zero) at launch with an HV pump, stock pan and windage tray. This was on street tires on Craig Road in Las Vegas, not even a track.  When I did the 489 later, I went with a Canton pan, and the baffling as well as increased capacity, although that copper line setup is gone now, I did do the same experiment when first assembled and it never wiggled. 

Now, did the HV pump make it worse or better in the original issue?  My guess is that it neither helped or hurt, the extra volume compared to a standard pump likely didn't go to the heads, it went out the relief, so IMHO it really was a supply issue.

[jayb]

I like to use high volume pumps because of the added safety factor in case of an engine failure.  Let's say you break a rockershaft and suddenly have a bunch of oil gushing out uncontrolled from the leak.  A high volume pump should be able to keep up with that and still supply the required oil to the rest of the engine, whereas a standard volume pump might not.  Same thing could happen with a spun bearing, a bent pushrod where the lifter pops out of the bore, etc. etc.

On pressure, I like to see 15-20 at idle and jumping right up to 50+ when you hit the throttle.  At highway speeds I like to see at least 60 psi, and no more than about 90 psi in any case, for the oil filter reasons described by Ross above.  A blown oil filter or oil filter gasket will wreck your day...

[blykins]

Most of my junk idles at around 20-25 hot and hits around 70 psi at full song.  I use mostly HV pumps but a HV pump does rob horsepower, so in some applications they are not warranted.

An engine is just a combination of controlled internal oil leaks.  If you have control over the bearing clearances, lifter clearance, oil to the top end, oil drainback, and a good quality pan, you can get away with a lot less. 

I've built drag race motors that have 55 psi crossing the stripe at 7500....oil pressure was measured at the rear of the engine, so I would imagine at the front near the pump, the engine is seeing around 65 or so.  On a freshen up, all the bearings looked excellent. 

[RJP]

Oil pressure is over rated... I've had tired engines [example: Q code 428 Galaxie] that had no oil pressure hot/idle, zero, nada.  Gauge read as if the engine was not running. Only had 20-25 lbs hot/freeway speed, I'm guessing 2500-2600 rpm.  The engine ran good, smooth, no knocks, taps, clicks, ticks, nothing. But that annoying red oil light bothered me. Rolled a set of rod/main bearings in, new Melling pump and waaa laaa...25-30 lbs hot/idle, 60+ hot/freeway speed. Made me feel better but did nothing for the engine, ran exactly the same. But on the other hand a fresh engine with correct clearance should have 15-20 hot/idle, 60+ freeway speed and should have at least 65-70 at max. rpm. I have 2 street driven only 427 sideoilers, both have the block relief valve stacked solid and rely only on the relief valve in the Melling HV pump. Both those engines have 20lbs hot/idle 65 hot freeway speed. As for the question I favor more volume using less pressure. I see no need for 90-100 lbs pressure in any engine, even a FE. Counter to old school thinking that FEs need lots of pressure they do just fine with the 10lb per 1000 rpm rule as with most other engines. The biggest "old wives tale" is FEs don't oil properly, hogwash, even a center oiler, whos oiling system looks quite similar to that of a small block Chevy which BTW is touted and bragged on as a great oiling system. So why is the SBC so good and the FE so bad? Circuitry is the same, only difference between the 2 is the location of the pump and the pan sump. Use a stock front sump 5 quart pan and see whats going to happen when you nail the throttle from a dead stop. FE=0 oil pressure, SBC= normal pressure. FEs used in flat bottom V-drives live long and happy lives under much harsher conditions than in cars because in those types of boats the engines are mounted backwards. Flywheel facing forward, sump and pump in the rear. Oil never leaves the pick up. Draw your own conclusion.   

[fekbmax]

Thanks guys for all the input.  Its always nice to hear what you had hoped to.
I remember Charlie Peppers mountain motor pro stocker having 8 - 10 lb of oil pressure idling.  I was like WOW . just as you guys have said though he said he would have about 110lb - 120lb going through the traps. I always loved those mountain motor pro stocks.. I hope they make a resurgence.