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Discussion Starter #1
My sbf 440 cube street car is having oil pressure fluctuations at the end of a 1/4 mile run between 8000 and 8500rpm. It has an external peterson oil pump with a modified canton oil pan. Recently it hurt some big end bearings from this issue These were replaced and the oil pan was further modified. I made an extra sump section to hold an extra 2.5 quarts (total of 11 quarts). Also did a kick out on the passenger side, gates, mesh windage tray and slotted tube pickup #16. Heads have external drain backs and max vac 15". The oil issue is still accuring. Unsure if it's running out of oil or the oil is aerated or overfilled or oil not staying where it should be. Any advise would be great.

Note: data logger white engine rpm, red driveshaft and green oil pressure.


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What is the oil pressure ?
I wonder if its just spinning the pump too fast at that rpm , might need a pully change to slow it down a little
 

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You might be hurting the bearings during the first 60 ft.
Where do you think all the oil goes during launch on a front sump ?
Straight to the back of the pan!
Might be worth looking into running an accumulator for this reason.
Something else that may be happening is that you have too much oil and it’s aerating from the crank action.
 

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Gday,
Good data mate, I think you need to look at it as a trend, what rpm are you at prior to leaving?
You are dropping oil psi from the start line onwards, It’s not rpm related or it should recover after the shift?
Unless you have a gforce / pick up issue or maybe you are a putting more oil to the top end than what you can drain back and are actually starting to suck air towards the end of the pass?
Good luck with it! Any pics of the pan / pick up etc?
What type of lifter and clearance?
Cheers
 

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Discussion Starter #6
This data log if after the oil pan upgrades. It's better but still not right.


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This data log if after the oil pan upgrades. It's better but still not right.


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Gday,
Yes better but not good, looks fairly rpm related there it’s not flash at the top of each gear.
Is it a fulll length pan? Hard to tell from those pics, no pics of the pickup and where it is?
No expert here but that pan doesn’t look real flash from above tray and screen wise
Cheers
 

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Shane have you checked that the oil isn’t being pumped to the top end?
We had this problem with my combo

Pull the intake off & valve covers the pressurise the oil pump with a drill & see what’s going on with the oil system
 

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Discussion Starter #9
Here is a shot of the external pickup and gate. This is a front sump design.


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Is it possible that your oil pan is holding a lot of oil in top section and not returning to lower section fast enough
Have you had engine on dyno to see if it still drops pressure ? That would help eliminate if it’s g force related
 

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Discussion Starter #11 (Edited)
Engine oil pressure was perfect on the engine dyno. I can't tell if the oil is not returning quick enough. The engine builder thought so which was why we gave it more oil capacity. It has 2 an8 oil returns from the heads to the pan. These both go to the drivers side of the pan and line up with a main cap.
Initially I though I ran too much vacuum and backed it up to 13". I also welded a an10 bung close to the pan rail so I could experiment with vacuum equalisation from the top to bottom of engine to aid oil return.
Not sure if I should run it again and experiment with lower and higher oil levels or its to risky.

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You have a TON of oil in that pan. Oil full of air bubbles compresses and you lose oil pressure. A crank scraper and less oil would do wonders.
 

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This is a log of mine with a mellings pump , canton front sump .
This is only too 8000rpm but has been to 8300rpm with no issues
Light Blue line is oil pressure which only changes 3psi through the entire run .
Seeing people have issues with an external pump makes me nervous of changing from internal on my new combo
 

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Discussion Starter #16
This is a log of mine with a mellings pump , canton front sump .
This is only too 8000rpm but has been to 8300rpm with no issues
Light Blue line is oil pressure which only changes 3psi through the entire run .
Seeing people have issues with an external pump makes me nervous of changing from internal on my new combo
Unfortunately I can't view your datalog. External pump pressure is linear with rpm with an adjustable max pressure. It only has 20psi hot at idle and peaks around 70psi. They will not flat line like a standard style pump.

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Discussion Starter #18
I think so but I didn't build it so I'm not sure.

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Only difference between internal and external pumps is the gearing, size of the pumping element and pickup.
Operation is identical , all depends on how you have it set up.
You either have an issue with the sump design / pickup or you are putting a heap of oil in the top end and the pump is starting to suck air, as I mentioned earlier , what lifters and what clearance?
I measure how much oil comes up one pushrod in a set time period using oil at operating temp and a flat tappet correct metering style lifter with the engine on the stand and priming it
I use that as my baseline
I then make sure the solid rollers do not exceed this amount, I then know I am good to go as far as not over oiling the top end
The difference will blow your mind
You need to know where you are there and your sump design needs to be right, no way do you require a huge sump like you have
The best thing you have done is with the data logger!😀
Good luck
Cheers 😀
 

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Discussion Starter #20
Only difference between internal and external pumps is the gearing, size of the pumping element and pickup.
Operation is identical , all depends on how you have it set up.
You either have an issue with the sump design / pickup or you are putting a heap of oil in the top end and the pump is starting to suck air, as I mentioned earlier , what lifters and what clearance?
I measure how much oil comes up one pushrod in a set time period using oil at operating temp and a flat tappet correct metering style lifter with the engine on the stand and priming it
I use that as my baseline
I then make sure the solid rollers do not exceed this amount, I then know I am good to go as far as not over oiling the top end
The difference will blow your mind
You need to know where you are there and your sump design needs to be right, no way do you require a huge sump like you have
The best thing you have done is with the data logger!
Good luck
Cheers
Thanks for the reply. It is a solid roller unsure of clearances. It doesn't appear to get to much oil to the top end when priming the engine with the valve covers off but I have not measured it.

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