David DeCan

In the midst of a 455 rebuild. Concerned about an oil pressure problem I experienced in a previous 455 build repeating itself.

Current build will use a Melling High Volume pump with bolt on pick up. Would like to use a stock 455 pan--non Toro. .0025 approx. main and rod clearances. I have read numerous threads here with differing opinions as to whether the stock pan will hold enough oil. Not really understanding why a high volume pump is not going to use more oil from the pan--thus "sucking" it dry in certain circumstances. I suppose the pump will only use as much oil as the passages will flow at a specified pressure??

Previous build used a Melling High Volume and Toro Pan. Bearing clearances .0025 approx. Don’t remember what the rod side clearances were on previous build but if memory serves I notched the big end of the rods and used press-in main saddle oil restrictors. Problem: Cruising on freeway at sustained rpm's of 3000 oil pressure would drop to 20 pounds and wobble around there. Start-up oil pressure was fine at 60 pounds. Idle oil pressure was fine at 30 or 40. Seemed like it was cavitating at the sustained rpms. Would back off the throttle and pressure would come back-up. Sustain 3000 rpms and pressure drop would occur again. Sold the car and never was able to investigate cause. As I remember the oil filter adapter was tapped and plugged as well.

Not against using a 7 quart Moroso pan, but it is really not that kind of car. Car is a 70 Convertible. 450-500 HP/500 Ft Lbs Torque, I would guess. Need to be able to cruise Montana freeways at 80 mph, top down, with solid oil pressure. Don't want a repeat.

Octania

"I suppose the pump will only use as much oil as the passages will flow at a specified pressure??"
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That is my understanding. The HV pump "can" flow more, if need be. What oil it does pressurize and flow, but cannot get out thru the engine's oil passages, is simply dumped back to the inlet across the relief valve, like any other such pump.



"Previous build used a Melling High Volume and Toro Pan. Bearing clearances .0025 approx. Don’t remember what the rod side clearances were on previous build but if memory serves I notched the big end of the rods and used press-in main saddle oil restrictors. Problem: Cruising on freeway at sustained rpm's of 3000 oil pressure would drop to 20 pounds and wobble around there. Start-up oil pressure was fine at 60 pounds. Idle oil pressure was fine at 30 or 40. Seemed like it was cavitating at the sustained rpms. "
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Sounds like maybe pickup too close to the pan. Pay close attention to that detail, and measure carefully. I think around 1/2" clearance is prudent.

rad

what part of Montana do you live in Dave?

bobus8

When I built my 455 using the melling HV pump, my machinist said to be sure to use a 7 quart pan as the pump can drain the pan at sustained highway speeds. Apparently, the 455's don't have good drain back and the oil stays in the valve covers. A little creative grinding and polishing in the return hole area of the heads can help drain back.

David DeCan

We live just outside of Missoula.

Yes, I have read the threads regarding oil pan being sucked dry. I don't know what to think. There seems to be just as many on the side that a stock pan with a HV pump is not a problem. I wonder if we could take a poll or something?

"How many are running a stock 455 oil pan--non Toro, and a Melling High Volume pump with no issues?"

Here is my problem--its a budget build. Moroso 7 quart throws another $300 at the issue. I just purchased a nice 455 non-Toro, original oil pan and I have the new HV Melling pump. Would like to use them. But on the other hand do not want to suffer what happened on the previous build---significant oil pressure drop at sustained higher RPM's. Really don't want to do this twice. Thank you your thoughts.

Don't know how to set up a poll. New to Classic Olds. Perhaps a moderator could help me with the poll? Thank you in advance. David DeCan

spooge031

I would install the restrictor kit from mondello performance, it is designed to keep oil directed at the mains and keep too much oil from getting to the upper end and chuck the high volume pump, high volume pumps in this engine will drain a stock oil pan fast and starve the engine bearings for oil, also be sure and deburr the block ESPECIALLY around the oil drain back, I am building a 455 for my second gen bird and this is also a budget build with me being most of the labor, but I can only afford to do it 1 time so anything to help with durability is going in.

TripDeuces

How much oil do you think gets through a lifter into the pushrod and then to the head?
How many threads have you read where people spin their drills for 15 minutes plus only to get a dribble of oil?
I'd like to hear from all the people who have sucked a pan dry and filled up their valve covers.
I'm calling BS on this.
If you take a pipe and increase it's diameter by twice you quadruple (that's 4x) the volume that can pass through it. EI 1 inch pipe to 2 inch pipe.
Eight 1/16 inch holes in the end of a pushrod aren't even close to the volume that flows through a 1/4 or 3/8 inch drain back hole. and you have two of those per head.

spooge031

it's a common failure and very well documented, on any olds engine ESPECIALLY a 455 that's turned over 5k the problem is oil does not return fast enough, ever try and adjust a valve on a sb chevy?you get SOAKED in oil there is a ton of oil getting to the heads

TripDeuces

Show me the facts.
This is another urban legend like headers won't fit a Cutlass S.
If this were the case then dyno runs would be dangerous for all Olds big blocks as well as driving at 70 mph with 4.10 gears. I've never heard of these failures.

spooge031

well then tell mondello performance you're better than they are, and know more than they do, enjoy I'm done debating with you I gave my opinion take it or leave it, btw how many years have you worked on cars? I have a quarter century under my belt

TripDeuces

Got you beat. I have over 40 years. Built my first Olds at 18. Sorry I hurt your feelings. I won't debate any longer either.

Fun71

Most of us here can do that.

You are obviously not aware of the extremely poor reputation "Mondello Performance Products" has in the hardcore Oldsmobile community.


edit:
I changed the above from "Mondellos" to "Mondello Performance Products" in order to differentiate the Paso Robles facility from the legendary Joe Mondello and his facility in Tennessee (Joe Mondello Racing Engines) that is still run by his family. I didn't want anyone reading this in the future to think I was disparaging Joe Mondello or his family's business.

David DeCan

Thanks for the replies. This is the problem: I don't want to finish this project and drive over to Interstate 90, top down, and set off for Seattle and get two miles down the road on Montana's newly crowed 80 MPH Interstate and watch my oil pressure skit skat around 5-20 pounds. Putting a 7 quart pan on and not seeing the problem doesn't answer the question either--possibly I did something haywire on the first rebuild. Maybe it was those notched rods? Maybe it was those oil restrictors? Maybe it was the plugged high pressure hole in the oil filter adapter? Maybe it was the .0025-.0035 clearances on the mains and rods? Maybe it was it was the Toro Pan with the scraper I put in?

Possibly this is how diagnostic work is done on an issue like this. It seems to be the way Dr. House operates--throw a fix at it and stand back and watch. I guess I am OK with that--you never really know if the stock pan would do the same thing unless one goes back and tests it as well.

You know what might help--could I hear from a few people who have Melling High Volume pump with a stock oil pan--non Toro? Did you have oil pressure problems? No mods to the oiling system. If I can get a few of you guys out there to confirm that the High Volume pump does not, cannot, pump the pan dry--I think the discussion is over. The answer that the factory put out thousands of stock oil systems out without these issues does not answer the problem--they used stock oil pumps.

Thanks for your help everyone who jumps in. If someone were inclined to set up a poll that would be helpful--not sure how to do that from here??

83hurstguy

Oil pan to pickup clearance. Check it, verify it... it's a surprisingly common issue.

You aren't going to pump all the oil into the valve covers with an HV pump. As mentioned above, you can only flow what the engine passages will support, and hydraulic lifters act like restrictors already.

Notching the rods can also cause a reduction in oil pressure (more area for oil to escape). That's an old school mondello deal that doesn't do you a whole lot of good. Obviously, small notches will have less impact than larger ones.

83hurstguy

Here's everything you need to know about Mondello Performance. Feel free to keep using them, the rest of us prefer to have our stuff last longer than 200 miles:

https://www.oldsmobilecentral.com/fo...ngine-had-.php

70cutty

The sad part is that this is just one of many, many cases.

TripDeuces

I met Joe Mondello at the Olds Nationals in Ohio. I really enjoyed talking to him and listening to his stories and vast knowledge of Oldsmobiles and all makes of heads he had ported throughout the decades. Until recently I even owned a set of his heads he had ported for me. I am not trying to disparage his good name in any way. His work speaks for itself.
I have not had any dealings with Lynn but the fact that Joe's son Bernard has distanced himself from the original Mondello business and started on his own may offer an explanation of that situation. Not my business.
Newer technologies today such as grooved and reduced feed hole cam bearings have basically addressed any oil restrictor issues from the past. If you think about it did the oil restrictors move any less oil than the original cam bearing hole anyway? The holes were about the same size.
A static Olds engine will not run the pan dry at any rpm as long as the oil pump pickup is at the proper height. There is a reason many pickups come with a strap to prevent the pickup from being too close to the pan floor.
Circle track and drag cars are a different story due to g forces acting on the oil itself. It's not uncommon for oil to climb 18+ inches up the rear of the block under hard acceleration like in a drag car. In circle track cars the oil climbs the side of the block much the same way and can cause problems. I good baffled pan and windage tray goes a long way here to keeping the oil around the pickup.
If you read several racing forums you see that racers who use these larger pans, 7-8 quarts or more, typically run 1-2 quarts lower than the max specified. This is due to windage and wanting to keep the oil level as low as possible in the pan. They sure aren't worried about sucking a pan dry.

bobus8

David
You have already experienced this problem first hand. Why do you even need advice on this subject. I know $300.00 is a lot of money but for your own peace of mind, just buy the pan and be done with it. Re pulling the engine at a future date to install a 7 quart pan just isn't worth not putting one in to begin with.
One more thing, check out the return passage in the cylinder head (it's not a straight shot) and remember that with the engine slanted up at the front, you don't start getting drain back from the front side until you have about an extra quart laying in each head.

bobus8

BTW, I used the Milodon MIL 30305 oil pan in mine. ($307.95 today from summit.)

TripDeuces

I have a HV pump in my engine but then again I have over size clearances. If your clearances are standard then a regular pump is more than enough. .001 per inch of bearing is fine for a standard pump.

If still not convinced then park in in the driveway and rev it to 3k rpm and observe the outcome. Did it lose pressure? Add a quart of oil and do it again, Did it lose pressure with more oil. Yes? Add another quart until it stops. Then you'll have you answer.
Honestly think how much oil are we talking about? Will the block hold a quart? Maybe.
Will the valve covers fill up? Doubt it but you'll see it at the breathers, etc. you have on the car if so. Sometimes you need to go outside the box but sometime not

MDchanic

Okay, I've been reading this BS-fest for a while now, and I have to say something.

How many here have ever sucked your pan dry? (Raise your hands!)
I have. Used to do it regularly in my Chevelle when I was a kid - the thing burned oil, and the way I'd tell it was low was when I'd go around a corner, the lifters would start ticking, and the pressure gauge would go to zero. I'd stop, get a couple of quarts out of the trunk, and pour 'em in.

That's what happens when you suck your pan dry.
It doesn't go to 20 pounds. There is no oil. It goes to zero.

If the pan isn't dry? Then you have oil, and you have normal oil pressure.

What about the pressure dropping at a certain engine speed because of poor drainback?
Well, let's think about it:

At a certain RPM, the engine can drain back more oil than it sends up.
All oil returns to the pan within a few seconds.
Oil pressure is not affected.

At a certain RPM, the engine equalizes - the drainage capacity and the pumping capacity are exactly equal. This occurs at one exact engine speed at a given engine temperature - not 5 RPM more or 5 RPM less.

Above this engine speed, more oil is pumped up than can drain down.
Slowly (or quickly, depending on RPM), the amount of oil in the valve covers increases, while the level in the pan decreases.
At a certain point, the level in the pan drops below the pickup, and the oil pressure does what?
Drops to zero.

It is possible that a low pickup could present enough of an obstruction to flow that the pressure drops at high RPMs, but it is not possible that a low pan level could do this.

Whether you are using a high or low volume pump has nothing to do with this, as the excess oil (effectively, the excess pressure) is simply shunted through the relief valve back into the pan (wasted horsepower) - if there is no excess, then it is all pumped through the galleries.
So a high volume pump will return more oil to the pan before it goes through the engine, and in the event of an intake flow restriction, that excess oil will just be pumped through the engine instead, until the restriction is so much that normal flow through the engine is affected (which is the same amount regardless of which pump you are using).

Any questions?

- Eric

Koda

Here's something else to consider. Big pans are designed for drag racers, with big pumps and big clearances and short duty cycles. Like Eric says, once the engine gets to pumping more up than gravity will drain down at that same time, the level in the pan will decrease. If you have that situation at steady operation on the highway, the only thing a bigger pan will do is lengthen the amount of time the pump has oil until it runs out, but it WILL run out.

If the engine returns 3 quarts of oil a minute (dumb number) and the engine pumps 4 quarts a minute above 4000 rpm up, then you look like this:

0 oil in pan = Pan Size (quarts) + 1/2 quart in filter - 1 quart per minute * the amount of minutes it takes you to run out. All a bigger pan does is work for short drag race sprints, and/or baffles and a bigger pan to avoid starving the pump on turns.

wr1970

I have a 7 qt pan on a 468ci no restrictors melling hv oil pump. I have drove this car 40 miles one way and never noticed a oil pressure drop. As a matter of fact says around 50/60 pounds at a sustained speed of 60/70 mph. When at idle it 30/40. I did do a oil mode to front drain smoothed it out nothing else. This is a street /race car 3750.

BlackGold

But just to be clear for everyone following along, your success is not because you have a 7-quart pan. Like others said, the bigger pan will delay "sucking the pan dry" (if the problem even exists), but cannot stop the inevitable at sustained high RPM.

mrw8i

I had rebuilt engine in my Denali. After the first oil change was done startup oil pressure was good, idle oil pressure was good, as it warmed up and got up to speed the oil pressure dropped and sometimes would go up and down; back to idle it went back up. The problem was too much oil. Fresh engine, the mechanic nor I could read the oil on the dip stick - too much was put in. The crank was dipping into the oil and cavitating the oil at high RPM. Drained 2 qts out and the oil pressure was good at all RPMs.