Slight Oil pres drop at higher rpms

[adsala]

Well, my repaired 460 is running fantastic. Thanks to you guys and this forum. I took out the boat two different times so far.
My other posts tells my story but to make it short I replaced my ruined cam with the same one, new lifters, rod/main bearings(plastigaged at .0025 rod and .003 mains), and a melling stock oil pump. I have a 10qt rear pickup Milodon oil pan. Running a small Ford type Napa/wix oil filter.
Now I'm wondering what's going on with my oil pressure. It stays around 45-50lbs hot up to 3400 rpms when I edge up to around 3800 it drops to around 40lbs. And maybe drops a little more up to 4500 or so. 800 rpm Idles at 20 hot and 75 cold. What's really weird is if I romp on it a little harder than what it takes to get on plane, the pressure goes up then momentarily drops to 25, then when I ease up on the throttle at plane, pressure edges up to 50. It's like it does the opposite of what you would expect.
I'm using 20w-50 valvoline as suggested by many others. The Milodon oil pickup is a good 3/8" off the bottom. And it has a small bracket welded to it about 1/4" off the botton to keep it from sucking pan. The only thing I can think of is maybe the Milodon pickup tube opening too small (about 1-.3/4""x2-1/2).
Could you guys, once again, give me some advice.

[Moneypitt]

Simple, 50 WT RACING OIL, brand really doesn't matter, 50 WT RACING OIL, this isn't you father's Oldsmobile, or T Bird, 50 WT RACING OIL..............RACING OIL, 50 WT, will also work.....MP

[HammerDown]

With those clearances, and their good...your fine with a straight wt oil. Like money said 50 wt is a good choice. Personally I use Kendall 40 with a touch of Lucas.
The one time I tryed 20/50 it turned into water...noisy lifters after a hard run and somewhat lower pressure.:eek:

[adsala]

Are you saying going from 20/50 to straight 50 is going to solve my oil pressure drop off when I rev it? That's what it does. When I rev on it hard the oil pres drops a little. My oil pressure never did this when I had the stock oil pan and pump running 15w/40. I don't understand.

[Rexone]

Originally posted by adsala
What's really weird is if I romp on it a little harder than what it takes to get on plane, the pressure goes up then momentarily drops to 25, then when I ease up on the throttle at plane, pressure edges up to 50. It's like it does the opposite of what you would expect.
This part sounds like a "pan design" problem...oil running away from the pickup. Is there baffles around the pickup in this oil pan? I don't think the multi-vis would cause this.
I agree the straight weight is a better choice though. However on the top end pressure drop, if it the viscosity causing it that is a function of increase oil temp and you would see it gradually, not immediate. Also when you backed out of the throttle with hot oil the pressure would not come back up fast like you're describing. That could also be pan design with the oil not around the pickup on acceleration. When you lose pressure due to thin oil it stays low till the oil cools off throughout the rpm range. Then when cool it comes back up throughout the range. What you're describing sound like more of a supply or clogged filter problem to me.

[Fiat48]

" My oil pressure never did this when I had the stock oil pan and pump running 15w/40."
Better look at the pan and the pickup for sure.

[058]

BBFs have a drain back problem from the heads. It sounds like the running oil level in the pan is low and the p/u is sucking air.

[adsala]

Now we're getting somewhere.
Rex,
Yes, right. The pressure is great at 3400 rpm a constant 50lbs. I guess if I was using straight weight the pressure would be higher. But it would still probably drop with higher rpms.
My oil pan has a baffle near the rear. I think it's about 3-4" from the pan's rear. It does not go all the way across about 2/3 and it has two flappers in it. And they are flapping great. It also has windage tray with three bolts holding it down. The rear part bolts to the top of the rear baffle. Sound ok?
058,
Low oil, been there done that ,but it is acting just like that, sucking air. The pan is rated for 10 qts and I have 11 in it. Any ideas how to prove that it's sucking air? Add more oil? I thought this was more of a problem with HV pumps. Oh ya I got EdelBrock Performer aluminum heads. Cost me a fortune!

[Jordy]

Silly question, but is it a jet boat pan? Which way do the baffles swing? The baffles could be keeping the oil out of the pump area, or at least slowing it's return.

[Rexone]

I still suspect a pan problem but without seeing the inside of the pan its a tough call.
Whatever you do don't overfill it. That is just about guaranteed to cause pressure problems caused by windage foaming up the oil.

[adsala]

Yes the pan is supposed to be a jet boat pan.
Here's a link to a picture. Once there click on view image for the bb-ford 429-460 pan. This is what mine looks like.
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=196254&prmenbr=361
As you can partially see. There is a small area for the pickup to go down into.

[adsala]

Man I think you guys are going to nail this one too! This has been a thorn in my side since I put the pan on. I wonder if Milodon has seen reports with this prob. I wish I had a better picture. The very rear of the pan has another horizontal baffle if you can see it in the Jegs picture. But only comes out a little with a small 90 degree bend at the edge.

[Jordy]

So you got the flywheel in the back pan? It will make a huge difference. And as Rexy said, overfilling it is just as bad and underfilling it because it will get in the rotating assembly and have a foam party.

[adsala]

Yes the Flywheel aft pan. I found others that are using it with no problems. I believe that my oil level is good. They say to use 10 qts. Actually it's riding a little low because of the filter. But not that low. I've experimented with the levels in the past to rid the presure prob. I would think that +or- 1qt shouldn't make too much difference.

[BrendellaJet]

Did you check the clearance between the bottom of the pickup and the pan?

[adsala]

The pickup is a little higher than 3/8" from the bottom. I just rechecked it. I looked through the drain hole. I stuck in a 3/8" socket extension and used the square end to measure it. It's just a little bit higher. I've had it at 1/4, 3/8 now a little higher. No fix. But keepem coming. There's got to be a solution right?
I'm going to call milodon tommorow. I followed all the instructions.

[Fiat48]

Milodon oil pan #31365
Pickup 18480 is specified to be used with Pump # 18845.
Not sure if Melling pump you have is compatable with the 18480 pickup, but be worth checking with Milodon to be sure.
Since the oil pump mounts at front of engine, and you have a jet boat, then the pickup would be long going back to the rear of the pan. I'm wondering about the possiblilty of sucking air at the pump bolt up or pickup bolt up area. Worth checking.

[058]

To expand on what Fiat said the next step is to check the oil pump clearances. Since you are drawing oil from the back of the engine to the front the oil pump pick up is quite long and a pump with tight clearances is much more important. A loose pump will not have enough suction vacume to draw oil thru the long pick up tube under accelleration/load. From some of the horror stories I've read about oil pumps and the "production" tolerances I'm surprised some of these pumps accually work at all. You might want to think about a blueprinted high volume pump for your engine.

[adsala]

Originally posted by Fiat48
Milodon oil pan #31365
Pickup 18480 is specified to be used with Pump # 18845.
Not sure if Melling pump you have is compatable with the 18480 pickup, but be worth checking with Milodon to be sure.
Since the oil pump mounts at front of engine, and you have a jet boat, then the pickup would be long going back to the rear of the pan. I'm wondering about the possiblilty of sucking air at the pump bolt up or pickup bolt up area. Worth checking.
I originally used the recomended milodon pump with the pan as part of the new rebuild. It did the same thing. So I decided to put in a Mellings pump hoping it would solve the prop. No go.
I really tried to do my homework before I posted this thread. What are the symptoms of sucking air at the attachments? I paid close attention when I bolted everything up. I used gaskets because they came with the pump. I put black sealer on the pickup to pump gasket. I've tried it with silocon only, gasket only, and combination gasket and silocon. Same prob
I had an old 78 blazer oil burner and when the oil got low the pressure would drop the same way. Look at the dipstick and yes it's low. Put in another couple of quarts and good to go. My 460 is acting just like that.

[Rexone]

Milodon boat pans are cheaper for a reason. IMO of course. ;)

[adsala]

Originally posted by 058
To expand on what Fiat said the next step is to check the oil pump clearances. Since you are drawing oil from the back of the engine to the front the oil pump pick up is quite long and a pump with tight clearances is much more important. A loose pump will not have enough suction vacume to draw oil thru the long pick up tube under accelleration/load. From some of the horror stories I've read about oil pumps and the "production" tolerances I'm surprised some of these pumps accually work at all. You might want to think about a blueprinted high volume pump for your engine.
This make sense a lot of sense actually. The original milodin pump that I used was HV. It was pressure dropping too. I was trying to make this story uncomplicated. I then used a mellings HV pump for about two years. The pressure did'nt drop but was only 40lbs max and I kept shearing the 1/8" distributor gear pin. Going to different distributor with the wrong gear height is why I had to put in a new cam. Long story but I've since put in a larger roll pin in the original distributor and stock pump. Maybe going back to a HV pump may fix it! But I want more pressure right? What should I do? How do you blue print a pump. Or better yet where do I get one. I'm really apprehensive about going to a HV pump. Many have said to use a stock pump because of pin shearing or dist gear wear.

[adsala]

Originally posted by Rexone
Milodon boat pans are cheaper for a reason. IMO of course. ;)
Ok, it's late but you guys are close to my solution. I feel it. And I really appreciate it. Ok, It's either the pump or the pan. Down to two things. At least you have not told me it's the bearings or something else. I can handle it now. I am going to have to probably pull the engine once more. I see that. Man! But I hope I do the right thing this time. Pulling the engine out three times in two weeks has killed me! I can get it out now in about 45 minutes. Geez I know this boat! I'm "one"with my boat and my wife hates it! But she's supportive because she likes the outcome and that's having fun.
So ask me more questions. What should I do next? I am desparate for a good boating season.

[Fiat48]

We are loosing the rabbit here.
Ford oil pumps are not a spur gear pump. The Ford division will have to chime in but they are superior to a spur gear pump. For more pressure you would shim the relief spring.
Pressure really wasn't the concern. It was the dropping of pressure.
"What's really weird is if I romp on it a little harder than what it takes to get on plane, the pressure goes up then momentarily drops to 25, then when I ease up on the throttle at plane, pressure edges up to 50. It's like it does the opposite of what you would expect."
To me....that says oil control or sucking air in the pickup tube.
All fords should have the chevy size roll pin. More Fords have died on the road from a sheared pin or a twisted oil pump drive shaft that anything else I would suspect.
What I was referring to on the pickup was this. Milodn specified the pickup was compatable with certain part number oil pump. That could mean that a standard or Melling replacement oil pump if used with the Milodon pickup could locate the pickup higher off the pan floor. You'd have to check with Milodon on that or compare the HV pump you had to the present low volume pump you now have.
As far as oil pump blueprinting, seems to me the cover clearance should be down to around .002 (like we do a chevy), check of the relief valve functioning and smooth and no cast slag or reduction areas in the outlet area.
Should be a gasket where the oil pump bolts to the block and also a gasket where the pickup bolts to the pump. Make sure that pickup tube gasket flange is flat and the gasket will seal it. Otherwise...it'll suck air.

[cstraub]

Sounds like turbulance around the pickup area. I would suggest putting some type of screen around the pickup area to reduce this. Since Melling is the only pump mfg. left, changing pumps is not going to do anything. Due to the low oil pressure, I would check a rod and main bearing just for piece of mind when you take her out.
Chris

[LakesOnly]

Adsala,
I'm ten minutes away...
PM me when you know you'll have your engine out. We'll look at your pan, pump and pick-up together; I've got the time. :cool:
I'm running the same pan, but a slightly different version (older design) with a Melling pump. My pump has no trouble pulling that column of oil through the pick-up for the length of the rotating assembly; hell, I've known the Melling pumps--in modified form--to pull a volume of oil though a pick-up tube 1.1" in diameter (and I'm expecting a case of those pumps to arrive at my place in a few weeks, by the way).
We'll go over your lubrication system together. Worst case scenario (I believe) will be another stock-specification pump that has been well inspected...but we may find the culprit to your problem before that's necessary.
LO

[Hallett19]

I am having a very similar problem however, not as extreme. My motor (460 BBF) pulls about 65psi at idle cold and 70 above idle cold. When warm, the least I see at idle is 35psi and above that around 55-60psi. However, when I am wide open, I run a touch below 50psi. Its strange, I have run lower oil, more oil, a quart low a quart high and it still did it. I want to change my filter to a Wix or k&n to see if that fixes anything, it seems my Fram could be at fault but I vaguley remember it having the same problem with a Mobil1 filter. Froggystyle and I had a funny problem while putting the pump and pan on my motor, I was drunk and being funny and I took his drill and put it on the drivshaft of the pump to spin it, the thing wobbled like a dead duck in my hands!!!!! SO WEIRD, so we went and got a new pump and it ran smooth with the drill attatched. I ran that pump and it caused the motor to ruin bearings. I run a dooley pan with a melling HV pump. I used krylon on the inside of the motor to aid in drain back. If you find a resolve to the problem, let me know.

[roostwear]

Here's my take on it (FWIW). I see 2 separate situations here... First is "It stays around 45-50lbs hot up to 3400 rpms when I edge up to around 3800 it drops to around 40lbs. And maybe drops a little more up to 4500 or so. 800 rpm Idles at 20 hot and 75 cold." This sounds like a temperature related drop in viscocity. I wouldn't tear down and start swapping pumps for this condition right away. First, I would switch to a synthetic or synth blend in a 40 wt. Personally, I hate running 50 weight mostly because of the additional strain on the pump/shaft to compensate for another problem. It takes more HP (transmitted thru the pump shaft) to pump 50 wt than 40. If a switch to synthetic/blend shows promise, I would consider adding a oil cooler.
Second, " if I romp on it a little harder than what it takes to get on plane, the pressure goes up then momentarily drops to 25, then when I ease up on the throttle at plane, pressure edges up to 50." In a starvation condition, you will see an initial increase in pressure on acceleration (as you'd expect), but if there is a drain back problem, the pressure would then drop as the sump level is lowered. As the rpm decreases (and also volume) the sump level will rise again.
I am assuming that the operating temperatures (oil) are normal when the pressure is acceptable, and as load increases (and oil temp rises) the symptoms are more pronounced.
Or not :D

[adsala]

I called Milodon. They said every now and then they get an engine with this problem. The guy said I'm pumping too much oil to the heads/ lifter valley. Same old story starving the pan of oil. He said the only way to fix it is to go to roller lifters and restrict the lifter gallies. I told him about some comments mentioned about possible pan problems. He got really on the defensive and said it was not the pan. At this point he gave me his credentials. I hate that. "I've been in this business for 15 years crap"!
But all in all he was trying to help me.
I told him my old front sump set up never had this problem. He said the rear sump has the longer tube which could create problems.
For one thing I cannot see how I am pumping most of the oil out of the pan into the top. With a stock pump?
He also said that I can get an anti cavitation pump where two slots are cut into the base plate. Well that's what my current pump has!
Many of you have mentioned putting in 40 or 50w straight or synthetic straight. He completely dissagreed that will solve my problem. I myself don't know since so many of you have suggested it.
Geez that's why I got a rear sump pan in the first place....to avoid this problem!

[blowngas]

not a ford guy but sounds like you have two things you have working against you-----hot oil (lower viscosity) resulting in lower pressure and oil not draining back to the pan----were you running the crank baffle with the other pan??----check and make sure there are more than one place for oil to come back down from the upper part-----install an oil cooler-----some of the oldsmobile powered jets down here in the texas badlands were having hell keeping oil pressure in their motors----cooling it down helped a lot and limiting some of the oil to the heads helped some too-----keep after it!!!!

[058]

As I said in my previous post about too much oil to the heads can be the cause of your pressure drop, this can be caused by aftermarket lifters with too big of oil feed hole to the pushrods. Having experenced this problem with a 460 in a car I restricted the oil to the heads by using restrictor pushrods and switching to roller rockers. If you notice the return holes in the heads are quite small and are designed to work with the engine level as it is installed in a typical Ford chassis. By installing the engine in a jet hull the engine is tilted to the rear several degrees overloading the rear drain hole and rendering the front hole useless. Just something else to think about.

[adsala]

Originally posted by blowngas
not a ford guy but sounds like you have two things you have working against you-----hot oil (lower viscosity) resulting in lower pressure and oil not draining back to the pan----were you running the crank baffle with the other pan??----check and make sure there are more than one place for oil to come back down from the upper part-----install an oil cooler-----some of the oldsmobile powered jets down here in the texas badlands were having hell keeping oil pressure in their motors----cooling it down helped a lot and limiting some of the oil to the heads helped some too-----keep after it!!!!
I don't think my oil pressure is too low. Is it? It's running at 50 or so hot at Rpms up to 3400 or so.
The problem is the pressure drops momentarily if I rev hard on it. If I'm easy on it the pressure stays around 45-50 all the time.
My old pan was a plain old front sump stock pan no with baffles. Worked great. Too bad I toosed it.

[roostwear]

Originally posted by adsala
Many of you have mentioned putting in 40 or 50w straight or synthetic straight. He completely dissagreed that will solve my problem. I myself don't know since so many of you have suggested it.
Geez that's why I got a rear sump pan in the first place....to avoid this problem!
My point in mentioning synthetic is to see if it lessens the condition. It's unlikely it will cure it, but will indicate if you're on the right track. Fuel dillution occurring because of low water temps will make it start dropping again, too. Ideally, (like that ever happens) you could regulate your water temp at 160 and run an oil cooler. What water temp are you running?
On a tangent, does anyone make a dry sump system for a 385?
Just my opinion....

[cook1]

I run the same pan on my 460 with the same heads and a hyd roller cam. Also about the same clearances on the bearings. Guess what, my oil pressure does the same thing only not as big of change. I run the stock oil pump and mobil1 15w50. My oil pressure will go from 65 to 45 when I go from 4000 rpm to 5000 rpm right away and goes back right away when I slow it back down. I run a remote oil cooler and filter so the oil has to go through 8 ft of line before it enters the engine. This coupled with the ford 460 not having very large internal oil passages for volume could be causing the problem. If you have a remote filter or cooler you may just have a volume issue.

[adsala]

Originally posted by 058
As I said in my previous post about too much oil to the heads can be the cause of your pressure drop, this can be caused by aftermarket lifters with too big of oil feed hole to the pushrods. Having experenced this problem with a 460 in a car I restricted the oil to the heads by using restrictor pushrods and switching to roller rockers. If you notice the return holes in the heads are quite small and are designed to work with the engine level as it is installed in a typical Ford chassis. By installing the engine in a jet hull the engine is tilted to the rear several degrees overloading the rear drain hole and rendering the front hole useless. Just something else to think about.
Ok restricted push rods may be worth a try and I don't have to pull the motor. Who carries restrictor push rods. And what size oil hole in the rod is considered restricted. Yes my heads have small return holes. Is there anything I can do there. Question, if my heads are filling with oil, why am I not seeing oil leaking all over the place like around the valve covers or out the breathers or PCV hole.
Still why would this prob pop up with rear sump oil pan? Did not have prob with old front sump pan. Still running stock pump. But everything else was stock too. (stock pushrods as well).
THIS MAYBE A PARTIAL SOLUTION!!! I need to figure out a method to test this theory though before I go off and buy pushrods. Need to measure the hole diameters in my current rods right? Please more help. I like this one.

[Hallett19]

if you have the 10psi per 1000 rpm's, you are still ok from what I understand. my motor pulls 4700 RPM's and I never see less than a butt hair under 50psi on the guage, thats good, right ? Even though the oil psi is higher at 4k thank 4700.

[cook1]

When I say volume issue I mean that your pump's internal bypass will open at about 70 psi and when you are running 4500 the oil pump pressure at the pump is probably 70 psi. It is just because of the volume required by the engine is more than the main passage from the pump to the motor will supply. So then you have a pressure drop after that point . Sinthetic oil will help as it did on mine. It now only drops about 10 psi. I have read that some engine builders say to drill out the supply passage to the engine because it is to small on the bbf.

[adsala]

I had to go to a really boring meeting and this gave me the opportunity to digest all the comments and think about the problem further.
The main problem:
Oil pressure drops on accelleration.
Here is what I think it's not:
-It's not the filter
-It's not the oil weight. (won't solve but may help)
-It's not the oil temp.
-It's not the bearing clearances.
-And I've changed my mind, I do not think I'm pumping all the oil to the heads.
Here is what I think it could be:
-Oil pump cavitation
-And/Or oil pick tube cannot keep up with demand
-Still could be pan design. But I'm thinking it's not.
My Milodon pickup to me seems pretty small. But the Milodon pickups are probably a proven design one would hope.
The bottom intake is a plate (about 1.5"x2.0") with a bunch of small round holes.
Fiat and 058 made some comments about the pump not having enough vacum/suction for the long tube under accelleration/load.
I'm starting to lean in this direction too.
So the question is, is it the pump cavitating(or has low suction)or is it the pickup not being big enough to supply flow.
Just as a comparison though, what is the typical dimensions of the opening of a rear sump pickup?

[adsala]

Here is what my pickup opening looks like. It's not my actual pickup. But the opening on this one is the same as mine.
http://store.summitracing.com/partdetail.asp?part=MIL%2D18425&view=257#largerimage

[Rexone]

Originally posted by adsala
Many of you have mentioned putting in 40 or 50w straight or synthetic straight. He completely dissagreed that will solve my problem. I myself don't know since so many of you have suggested it.
I agree with him on that one point. It's a good thing to do IMO but it isn't your problem.
I stand by the oil strarvation track I posted on above due to pan design or possibly the oil not draining back theory.

[adsala]

Originally posted by Rexone
I agree with him on that one point. It's a good thing to do IMO but it isn't your problem.
I stand by the oil strarvation track I posted on above due to pan design or possibly the oil not draining back theory.
Rexone,
I just read up on the dooly oil pan pitch on your web site. This is very tempting. The pitch mentions "The oil needs to stay in the pickup area". So have you seen my problem before?. And has an oil pan upgrade solved it? Can you PM me with a price.
I am still not sure it's a drainback problem. Because accellerating quickly from idle makes the pressure drop slightly and immediately. Probably not even enough time to fill the top end and empty the pan. The harder I accellerate from idle the lower the pressure drops.
I had a 68 camaro with a HV pump and it used fill the top end but under high rpms. The pressure would drop almost to zero! Mine only drops a little if I gradually increase to higher RPMs maybe to 39lbs or so.

[396_WAYS_TO_SPIT]

Originally posted by adsala
I had to go to a really boring meeting and this gave me the opportunity to digest all the comments and think about the problem further.
The main problem:
Oil pressure drops on accelleration.
Here is what I think it's not:
-It's not the filter
-It's not the oil weight. (won't solve but may help)
-It's not the oil temp.
-It's not the bearing clearances.
-And I've changed my mind, I do not think I'm pumping all the oil to the heads.
Here is what I think it could be:
-Oil pump cavitation
-And/Or oil pick tube cannot keep up with demand
-Still could be pan design. But I'm thinking it's not.
My Milodon pickup to me seems pretty small. But the Milodon pickups are probably a proven design one would hope.
The bottom intake is a plate (about 1.5"x2.0") with a bunch of small round holes.
Fiat and 058 made some comments about the pump not having enough vacum/suction for the long tube under accelleration/load.
I'm starting to lean in this direction too.
So the question is, is it the pump cavitating(or has low suction)or is it the pickup not being big enough to supply flow.
Just as a comparison though, what is the typical dimensions of the opening of a rear sump pickup?
This sounds logical to me but I have the same problems and I have a stock pick tube on my pump.I have tried more oil,less oil, and no luck. I think my problem maybe the water my cabs were dumping into my oil:eek: Just an idea though.
396

[seho]

Have you changed oil sending unit (electric) or gage? I posted this once before I think but here goes. I ruined a crank once and had to rebuild. First trip out after new engine I watched the oil press. like a hawk..start up at 55 psi. and when it warmed up it dropped to 50 ish. So far not too bad BUT after running across the lake it dropped to 45 and I noticed that when I accelerated from a low rpm the oil press. would rise to about 55 and then drop to 40 after 15 seconds or so and if I stayed on the throttle it would creep down to 25 before I'd back out of it. Oil press would rise back to 45-50. Accellerate again, same scenario. I figured I had another 'drain back problem' (Olds engine) and was about to get seriously pissed. Long story short (after tearing down a ways not to find a thing wrong with the engine or components) I remembered that I had put in a new gage, 0-80 psi. but my sending unit was for a 0-100 psi gage. I found a sending unit for a 0-80 psi. gage and now Im reading 70 psi. on start up and it runs a constant 65 psi all day long and no engine problems to date.

[Rexone]

I've seen, heard of, and dealt with customer's oil starvation problems for about 25 years now. Inadquate oil to the pickup due to various problems covers about 90% of what I've seen. One of the main areas is poor oil pan design or should I say un-optimum oil pan design. I've sold Dooley, Olson, and Avaid pans for a long long time and never have had anyone complain about an oiling problem that ended up being due to these pans designs. I have seen and heard of many problems with the brand you are running and others as well although I have never run or sold them. The bottom line is that if the oil is not kept concentrated around the pickup during acceleration, deceleration, and hard cornering, YOU WILL have oil pressure problems at least momentarily during these extreme events (extreme for oil control). That is my view on the oil pan topic.
Whether it's your problem obviously I'm not 100% sure. I feel its high on the probability list though based on the above. Hope that helps you.
Problems that are common other than pan design that I've seen, in no particular order of popularity...
Silicone partially plugging the oil pickup
Cracked tube on oil pickup
Pickup mounted too close to pan bottom
Pickup loose on pump sucking air
Too high oil level allowing windage to foam up the oil
Too low oil level allowing the pump to suck the pan dry
Inadequate oil drainback at high rpm
Fram (primarily) oil filters clogging up
Water in the oil clogging any filter up
Shitty oil pump
Shitty oil or too low viscosity for application
Oil too hot causing pressure drop
Wrong bearing clearences
poor oil pickup design
There are probably some others. Those are the ones that immediately come to mind.

[adsala]

Originally posted by seho
Have you changed oil sending unit (electric) or gage? I posted this once before I think but here goes. I ruined a crank once and had to rebuild. First trip out after new engine I watched the oil press. like a hawk..start up at 55 psi. and when it warmed up it dropped to 50 ish. So far not too bad BUT after running across the lake it dropped to 45 and I noticed that when I accelerated from a low rpm the oil press. would rise to about 55 and then drop to 40 after 15 seconds or so and if I stayed on the throttle it would creep down to 25 before I'd back out of it. Oil press would rise back to 45-50. Accellerate again, same scenario. I figured I had another 'drain back problem' (Olds engine) and was about to get seriously pissed. Long story short (after tearing down a ways not to find a thing wrong with the engine or components) I remembered that I had put in a new gage, 0-80 psi. but my sending unit was for a 0-100 psi gage. I found a sending unit for a 0-80 psi. gage and now Im reading 70 psi. on start up and it runs a constant 65 psi all day long and no engine problems to date.
Yes I did replace the sender on the new rebuild. But I swear I got the right sender. I can't believe this would be my problem so I set out to test your theory. I could not find a part number on my sender but it has 80 mexico on it (as in 80lbs?). regardless I looked up the specs on the teleflex senders. Both the 80 and 100 lb senders are rated at 240-33ohm signal. So I fired up my air compressor to use as a pressure supply to test my current sender. I rigged up a pressure connection to the sender right at the compressor. Then I tracked down the multimeter and hooked it up and low an behold I got some interesting readings. I set the pressure to 100psi and the ohm meter read ~240-30. When I set it to 80 I got, get this, 240-45ohms! According to those readings I got a 100lb sender. Man! you may have solved my problem. I am going out to get a new sender tomorrow. I'll let everyone know if this solved the problem once I can get the beast on the water again. I am still in denial! But there is hope.
Does a 100lb sender cause an 80lb gauge to overload thus showing drop in pressure? W'ell see.

[Rexone]

I've seen mismatched senders cause some strange readings. Make SURE you get the sender that is intended for your particular brand of Gauge. Senders vary between manufacturers even for the same range gauges depending on the calibration of the gauge.

[cstraub]

I would not say that it is a drain back problem of the oil. . .if it was it would have also been a problem with the old pan.
Restrictor pushrods are made by Smith Brothers. They run about $10 a rod. I don't feel this is going to solve the problem.
Chris

[CustomCruiser]

I am running the same type of oil pan (Milodon - flywheel aft) in my Merlin III 540 and I have not experienced any oil pressure problems.

[adsala]

Sending unit is correct. It was a matched set when I purchased it. I recall the reason why I even replaced the guage and sender in the first place was because of the pressure drop readings. My memory is going! Oh well. So I'm starting to really lean toward the oil pump.

[adsala]

From Rexone:
Problems that are common other than pan design that I've seen, in no particular order of popularity...
My responses. If you are interested please read carefully. You may see something wrong which may help me.
Silicone partially plugging the oil pickup
-Mine is clean
Cracked tube on oil pickup
-No cracks
Pickup mounted too close to pan bottom
-at 3/8"
Pickup loose on pump sucking air
-Pickup not loose. Verified
Too high oil level allowing windage to foam up the oil
-Pan Rated 10qts ~2-1/4" oil level at pickup location with level pan. Is this right?
Too low oil level allowing the pump to suck the pan dry
-See above. But pressure drops quickly from hard loading off idle too! Is this quick enough to empty pan?
Inadequate oil drainback at high rpm
-Never had this problem before
Fram (primarily) oil filters clogging up
-not using Fram
Water in the oil clogging any filter up
-not a drop of water in oil
Shitty oil pump
-BIG POSSIBILITY. New mellings stock pump currently installed.
Shitty oil or too low viscosity for application
-20w-50 Racing Valvoline
Oil too hot causing pressure drop
-never ran too hot before. But I have not measured
-Still Getting 50lbs at boat planing RPMs (3500)
Wrong bearing clearences
-bearing are clearances correct. Pres would be low all the time if clearences or loose. Right?
poor oil pickup design
-BIG POSSIBILITY. Like I said before.
And Rexone says my pan could have flow problems too. What should I do? Replace the whole system with a Rex-Marine dooly pan and replacment pump?
I thinks we have narrowed it down pretty good though. Pan, Pump, or Pickup. Or a combination of the three. What to do what to do?

[roostwear]

I have a 460 in my Advantage with a pressure loss problem similar to yours. I have done to my boat what I suggested you do, and am positive the biggest contributor is viscocity loss due to heat. I even have a dooley pan and pickup. When I shut down for an hour or so, the pressure is fine until I'm just on plane (or faster) and it builds heat. I suspected the pickup in the beginning, but after measuring the oil level in the pan, found that the pump is partially submerged, and the pipe (that's bolted to the bottom of the windage tray) is near the oil level. The pickup pipe diameter is larger than an automotive pickup so I discounted that reason. I changed from a dyno based oil to synthetic, and the condition was much better (but still there to a degree). The more hours on the oil, the more drop I'll get.... I assume from fuel dilluting the oil in time (I run it too cold).
At idle, the oil level is not at the level on the dipstick, it's a little lower due to normal circulation. As you accelerate, the oil level will drop further as higher rpm will produce greater volume. A high volume pump will displace an even greater volume at a given rpm, with the drain back volume limited by the size of the drain holes. Easing into the throttle would cause less volume to be sent to the top end than if you stabbed it hard, but is it the basis of your problem? I don't know. It may contribute to it, but to me, loss of viscocity would seem the more logical reason.
I don't know what effect the Milodon pan is having on your situation as I've never run one. The problem is, most of the advice in this thread is theoretical, although based on reasonable logic. The only way I can narrow my condition down more is to add a cooler, and test it again.
Just another .02

[adsala]

Originally posted by roostwear
I have a 460 in my Advantage with a pressure loss problem similar to yours. I have done to my boat what I suggested you do, and am positive the biggest contributor is viscocity loss due to heat. I even have a dooley pan and pickup. When I shut down for an hour or so, the pressure is fine until I'm just on plane (or faster) and it builds heat. I suspected the pickup in the beginning, but after measuring the oil level in the pan, found that the pump is partially submerged, and the pipe (that's bolted to the bottom of the windage tray) is near the oil level. The pickup pipe diameter is larger than an automotive pickup so I discounted that reason. I changed from a dyno based oil to synthetic, and the condition was much better (but still there to a degree). The more hours on the oil, the more drop I'll get.... I assume from fuel dilluting the oil in time (I run it too cold).
At idle, the oil level is not at the level on the dipstick, it's a little lower due to normal circulation. As you accelerate, the oil level will drop further as higher rpm will produce greater volume. A high volume pump will displace an even greater volume at a given rpm, with the drain back volume limited by the size of the drain holes. Easing into the throttle would cause less volume to be sent to the top end than if you stabbed it hard, but is it the basis of your problem? I don't know. It may contribute to it, but to me, loss of viscocity would seem the more logical reason.
I don't know what effect the Milodon pan is having on your situation as I've never run one. The problem is, most of the advice in this thread is theoretical, although based on reasonable logic. The only way I can narrow my condition down more is to add a cooler, and test it again.
Just another .02
Thank you very much for your input. Your idea won't hurt to try. But what if I told that it happens immediately when the oil only warm not hot? I did'nt try it yet but, I bet you it would still drop. You said your problem goes away after an hour or so after the oil cools down. You mean that you get NO oil pres drop on accelleration when the oil is warm?
Why am I having these problems since the pan upgrade? There were no oil pressure drops with the old front sump stock pan running 10w-40. So I'm not sure it's a viscosity problem.
Another thing is the pressure drop is pretty constant. Never goes below 25lbs on hard acceleration from idle only. After an hour of drive time!
I promise when I find a solution, I will post it.

[powerplay230]

Have you thought of switching pan back to original setup and see if problem goes away. don't know if that's possible but one way to isolate the problem?

[adsala]

Originally posted by powerplay230
Have you thought of switching pan back to original setup and see if problem goes away. don't know if that's possible but one way to isolate the problem?
Old pan is long gone. I thought of this. Would be a good test. But I'm pretty sure that the old setup would have worked ok. I did not do anything else really major to my engine to affect oiling except the pan upgrade.

[powerplay230]

Dean,
Just looked at your site, sweet job redoing the boat... that your line of work or just a personal project?
:D

[adsala]

Originally posted by powerplay230
Dean,
Just looked at your site, sweet job redoing the boat... that your line of work or just a personal project?
:D
Personal project. Thanks