460 oil pressure issue starting at 4600 RPMs

How exactly would a high capacity pan cause this RPM related problem?

They do have a trap door type box around the pickup. Should that door be taken off? What reason do you have for the pan being the issue??

Yeah Do tell Paul... How's the Pan the issue?

Had a similiar problem on a v-drive boat with a 396 chev. It too had an oil pan with the flapper doors around the pickup. The problem ended up being a leak in the pickup tube. At higher RPM more oil was up in the top end and less in the pan. This exposed the crack in the pickup tube allowing it to draw in air.

I've also seen motors with excess blowby cause poor oil drainback and lose oil pressure at high rpm's. The blowby gases going up through the block prevents the oil from draining back down into the pan.

Try overfilling the engine a little and see if it changes the symptoms.

Does the Oil Pressure pick back up again ABOVE 4,700 rpm's?

Originally Posted by Motorhead

How exactly would a high capacity pan cause this RPM related problem?

Originally Posted by FEandGoingBroke

Yeah Do tell Paul... How's the Pan the issue?

There's a lot more to a proper oil pan than increased/high capacity, and in this case it ain't got nothing to do with capacity at all...it has a lot more to do with the specific design relative to the application.

Originally Posted by electrowoman

They do have a trap door type box around the pickup.

Hardly, and your oil pressure symptoms are proof of that. What they have for collecting oil around the pickup is barely boxing the oil in at all....if you can even call it "boxing."

Let me first start by saying that 8 out of every 10 engines that we build are marine engines, and 7 out of those 8 are jet boat engines. A recent jet boat engine that we built is currently posted in the dyno section of this Forum and may be viewed by clicking HERE (By the way, the engine build in the link holds 80+ psi oil pressure all the way to 6000+ rpm with all bearing clearances at 0.003" or greater.)

We have heard of more oil pressure related issues in the 460 Ford jet boat engine using the Milodon pan than any other jet boat pan available. That being said, my very own jet boat uses the Milodon and I don't have oil pressure problems.

Electrowoman, I dare you to do this: next time you go out, have your friend drive the boat and you ride shotgun. While sitting in the passenger seat, place a 10-gallon fish tank in your lap, fill it with 20w-50, and have your friend nail the throttle. You'll get a really good idea of how difficult it is to control all that oil in a speed boat because if you actually dared do this you would be covered in 10 quarts of 20w-50. (So don't really do it!) Boat's launch hard, run hard and hop wakes and swells all day long and technically are subjected to more random bucking and bouncing than most any street driven vehicle and a lot of asphalt racing vehicles too. Oil control is ever more critical and ever more tricky in a marine application such as a jet boat.



I truly wish I had a picture of my pan (below) with the windage tray off of it, but I don't.





In the above picture, the front of the pan is to the left and the rear of the pan is to the right. At launch, oil indeed sloshes toward the rear. Beneath the windage tray is a couple of trap doors that prevent the oil from passing back (forwards) through the trap doors at decelleration, but the walls of the trap doors do not cross the entire bottom of the pan, so want's to stop the buildup of oil from travelling around the open portion of the pan and away from your pickup??? This is just an description/example to allow everyone to understand one aspect of this particular pan's design.

We've discussed the lack of adequate baffling and boxing; now lets add two more culprits: 1) the windage tray is not full coverage / fully protecting the sump from the crank windage, and, 2) when you launch you can bet that a LOT of oil has climbed up the back of your pan, and has travelled up the backside of the cylinder block (if you don't believe me than try that fish tank thing) and has further been drawn into your rotating assembly (thereby reducing the amount of oil in the sump).

So now, your 4000+ rpm spinning crank has a roping effect--like a horizontal tornado--that is somewhat preventing your oil from returning to the pan. Add to this that the small amount of oil remaining in the sump is resultingly so little that it can actually be drawn up into the crank windage.

The reason that the baffles & gating do not cross the entire floor of the pan is because the pickup tube essentially runs along the bottom of this pan where there is no windage tray.

There are several ways to correct this: One is to box the oil in the pan better, and the other is to reduce windage to the sump/minimize windage. In my case, my crank has been heavily streamlined and windage is reduced. But I have known others that tried a lot of things and simply could not alleviate the problem until they changed oil pans.

Your symptoms are beginning to occur at an rpm that is about as low as I have seen, but I have known this to happen to another guy at cruise speed (~4000 rpm)...took awhile but eventually acted up, then he'd bring the boat to a rest and oil pressure builds again once oil is collecing in the pan.

One last thing: with all these severe forces going on in your crankcase, you can bet that your oil is taking a severe beating and getting aerated, which will show up as reduced oil pressure, too.

My advice is to remove the pan and modify it so as to better "box in" the oil that it holds. If you don't feel that you are up to the mods and/or cannot determine how to improve the pan, then buy a new pan. I strongly recommend an Armando's 10-quart pan. The windage tray sits atop full-pan-width gates and it also covers the entire perimiter of the pan. Oil is truly boxed in and has nowhere to go except for up the pickup tube.

Paul

Originally Posted by Blulakr

Had a similiar problem on a v-drive boat with a 396 chev. It too had an oil pan with the flapper doors around the pickup. The problem ended up being a leak in the pickup tube. At higher RPM more oil was up in the top end and less in the pan. This exposed the crack in the pickup tube allowing it to draw in air.

I've also seen motors with excess blowby cause poor oil drainback and lose oil pressure at high rpm's. The blowby gases going up through the block prevents the oil from draining back down into the pan.

Try overfilling the engine a little and see if it changes the symptoms.

All good points.

Paul

p.s.: Post some pics of your boat, here are some pic's of one of mine (jet boat):

Im no expert, but pauls defination makes sense. the only thing i thought of is that she said it happens ANYTIME the RPM goes about that 4600. Maybe she just wasnt being as specific as possible, but she didnt say from 4000-5000, it was right at the 4600, like an on off switch. I doubt it would be the pan baffleing or lack of with such a consistant thing. Try getting the boat up on plane on a smooth lake, taking it easy getting up there so you slosh the oil out as little as possible. Get on plane and leveled out at about 4000 rpm, and slowly climb up to 4600 or whereever the pressure usually drops. See what happens, if it doesnt drop, its oil sloshing around. If it does drop right at 4600 like clockwork, then its probably not it.

If it was oil sloshing away from the pickup it would happen at a much lower rpm on takeoff than it would at crusing, it wouldnt be consistant througout.

I have no idea if the pressure comes back up at higher rpms, when the pressure drops so does my desire to push it. I back off a bit and the pressure comes right back. I ordered another oil pump to try and I'll check the tube to see if I can tell if it's leaking somewhere.

I don't want to hurt this motor.