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BBC oil restrictors

General engine tech -- Drag Racing to Circle Track

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70MC
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BBC oil restrictors

Post by 70MC »

I bought a used GM 572 crate motor and changed heads (AFR), cam (solid roller by Jones),lifters (Crower), rocker arms (Crower shaft), oil pump (Titan) and oil pan (Milidon).
I ran the motor with the changes I listed with exception to the oil pump and pan with no problems. I then added the Titan pump and the Milodon pan and immediately had an oil pressure problem. The problem was an oil pressure fluctuation while steady cruising at 55mph, the rpms are around 2500, cant remember exactly. The oil pressure was bouncing from 50-to 60 lbs, and gets worse with rpms.

I sent the pump back to Titan to have inspected since I was sure there was something wrong with it because I ran this motor for a few years and it never had this problem prior to the the pump and pan change.
He found the pump to be in perfect working order and said I am not draining oil back to the pan fast enough and sucking air due to the volume of oil this pump is capable of. That answer surprised me, but I believe him. He is recommending oil restrictors, and doing what I can to ensure oil drain back. I removed the heads to enlarge the drain back holes, removed the valley screens and am seriously considering external drain back lines.

This motor is in a street strip car and may see many miles at hours at a time on the freeway. I have no experience with oil restrictors, or external dran back lines. I see Moroso makes them for the Gen VI Bow Tie motor with a .0625 orifice that can be drilled larger if needed.

I am looking for everyones thoughts on this, and recommendations for the restrictor size and external drains?
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Re: BBC oil restrictors

Post by Racing68 »

What part number pan? Avoid restrictors if possible since it will see highway driving, you will need more oil to the springs to keep them cool during long running periods.
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Re: BBC oil restrictors

Post by Belgian1979 »

70MC wrote: Tue Jun 30, 2020 1:07 pm I bought a used GM 572 crate motor and changed heads (AFR), cam (solid roller by Jones),lifters (Crower), rocker arms (Crower shaft), oil pump (Titan) and oil pan (Milidon).
I ran the motor with the changes I listed with exception to the oil pump and pan with no problems. I then added the Titan pump and the Milodon pan and immediately had an oil pressure problem. The problem was an oil pressure fluctuation while steady cruising at 55mph, the rpms are around 2500, cant remember exactly. The oil pressure was bouncing from 50-to 60 lbs, and gets worse with rpms.

I sent the pump back to Titan to have inspected since I was sure there was something wrong with it because I ran this motor for a few years and it never had this problem prior to the the pump and pan change.
He found the pump to be in perfect working order and said I am not draining oil back to the pan fast enough and sucking air due to the volume of oil this pump is capable of. That answer surprised me, but I believe him. He is recommending oil restrictors, and doing what I can to ensure oil drain back. I removed the heads to enlarge the drain back holes, removed the valley screens and am seriously considering external drain back lines.

This motor is in a street strip car and may see many miles at hours at a time on the freeway. I have no experience with oil restrictors, or external dran back lines. I see Moroso makes them for the Gen VI Bow Tie motor with a .0625 orifice that can be drilled larger if needed.

I am looking for everyones thoughts on this, and recommendations for the restrictor size and external drains?
Just my .02$.

A pump will pump the maximum it can at a given rpm as it is a positive displacement pump. Always. Most pumps volume vs rpm diagram will show you that it will reach maximum volume at around 1300-1500 rpm. All it will do, when it pumps more volume than the engine needs (which depends on internal clearances) is raise pressure. It will do that until the point when the bypass will open. At that point, all of th excess will be pumped back into the pan. So in principle there is not such thing as sucking the pan dry.

A couple of things could be the problem here:
- incorrect installation of the pump screen versus the pan (not deep enough or too close to the floor of the pan).
- if suction is so strong and the pan has a large surface it could suck up the floor of the pan thereby decreasing the distance to the screen. This can be solved by welding nuts to the screen that prevent the floor from coming too close.
- Incorrect oil level in the pan.
- aeration of the oil due to the crank whipping up the oil and turning it into foam (check if the oil level in the pan is correct and the oil is below the pan baffles.

Long time ago I witnessed a similar problem on mine but it did so at high rpm. The root cause was that I neglected to test the contence of the pan before I mounted it. So I poured in the amount of oil that the manufacturer of the pan said it could contain and I marked the dipstick. I found out that amount of oil would actually make the oil level sit above the baffle of the pan. (courtesy of Kevin Johnson who gave me this advice) I adjusted the oil level to the correct height while measuring the amount of oil. I then remounted the pan, filled it up with the required amount of oil after my test. Remarked the dip stick and never had to look back again.
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Re: BBC oil restrictors

Post by 70MC »

Racing68 wrote: Tue Jun 30, 2020 1:53 pm What part number pan? Avoid restrictors if possible since it will see highway driving, you will need more oil to the springs to keep them cool during long running periods.
The pan is their pro competition pan part number 31185. I always thought the same as far as the restrictors go.
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Re: BBC oil restrictors

Post by 70MC »

Belgian1979 wrote: Tue Jun 30, 2020 2:38 pm
70MC wrote: Tue Jun 30, 2020 1:07 pm I bought a used GM 572 crate motor and changed heads (AFR), cam (solid roller by Jones),lifters (Crower), rocker arms (Crower shaft), oil pump (Titan) and oil pan (Milidon).
I ran the motor with the changes I listed with exception to the oil pump and pan with no problems. I then added the Titan pump and the Milodon pan and immediately had an oil pressure problem. The problem was an oil pressure fluctuation while steady cruising at 55mph, the rpms are around 2500, cant remember exactly. The oil pressure was bouncing from 50-to 60 lbs, and gets worse with rpms.

I sent the pump back to Titan to have inspected since I was sure there was something wrong with it because I ran this motor for a few years and it never had this problem prior to the the pump and pan change.
He found the pump to be in perfect working order and said I am not draining oil back to the pan fast enough and sucking air due to the volume of oil this pump is capable of. That answer surprised me, but I believe him. He is recommending oil restrictors, and doing what I can to ensure oil drain back. I removed the heads to enlarge the drain back holes, removed the valley screens and am seriously considering external drain back lines.

This motor is in a street strip car and may see many miles at hours at a time on the freeway. I have no experience with oil restrictors, or external dran back lines. I see Moroso makes them for the Gen VI Bow Tie motor with a .0625 orifice that can be drilled larger if needed.

I am looking for everyones thoughts on this, and recommendations for the restrictor size and external drains?
Just my .02$.

A pump will pump the maximum it can at a given rpm as it is a positive displacement pump. Always. Most pumps volume vs rpm diagram will show you that it will reach maximum volume at around 1300-1500 rpm. All it will do, when it pumps more volume than the engine needs (which depends on internal clearances) is raise pressure. It will do that until the point when the bypass will open. At that point, all of th excess will be pumped back into the pan. So in principle there is not such thing as sucking the pan dry.

A couple of things could be the problem here:
- incorrect installation of the pump screen versus the pan (not deep enough or too close to the floor of the pan).
- if suction is so strong and the pan has a large surface it could suck up the floor of the pan thereby decreasing the distance to the screen. This can be solved by welding nuts to the screen that prevent the floor from coming too close.
- Incorrect oil level in the pan.
- aeration of the oil due to the crank whipping up the oil and turning it into foam (check if the oil level in the pan is correct and the oil is below the pan baffles.

Long time ago I witnessed a similar problem on mine but it did so at high rpm. The root cause was that I neglected to test the contence of the pan before I mounted it. So I poured in the amount of oil that the manufacturer of the pan said it could contain and I marked the dipstick. I found out that amount of oil would actually make the oil level sit above the baffle of the pan. (courtesy of Kevin Johnson who gave me this advice) I adjusted the oil level to the correct height while measuring the amount of oil. I then remounted the pan, filled it up with the required amount of oil after my test. Remarked the dip stick and never had to look back again.
Your thinking is the same as I thought when it comes to pumps and sucking the pan dry. It was a small twist when I started reading of drain back issues.
The pump and pickup is integral, and matched to the pan depth. I will have to look at my specs but the distance of the pump to pan was a little further than I am use to, it was 1/2 maybe 5/8, I will have to double check to be certain, but again, I do remember it being a little further than what I am use to.
I had a windage issue in my 420 sbc that was solved by removing 1 quart and running 6 quarts instead of 7. That problem showed up at higher rpms. Ever since then I filled my pans up on the bench prior to install to be sure they were not to full. 7 quarts and this pan was full to the tray.
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Re: BBC oil restrictors

Post by mt-engines »

70MC wrote: Tue Jun 30, 2020 7:04 pm
Belgian1979 wrote: Tue Jun 30, 2020 2:38 pm
70MC wrote: Tue Jun 30, 2020 1:07 pm I bought a used GM 572 crate motor and changed heads (AFR), cam (solid roller by Jones),lifters (Crower), rocker arms (Crower shaft), oil pump (Titan) and oil pan (Milidon).
I ran the motor with the changes I listed with exception to the oil pump and pan with no problems. I then added the Titan pump and the Milodon pan and immediately had an oil pressure problem. The problem was an oil pressure fluctuation while steady cruising at 55mph, the rpms are around 2500, cant remember exactly. The oil pressure was bouncing from 50-to 60 lbs, and gets worse with rpms.

I sent the pump back to Titan to have inspected since I was sure there was something wrong with it because I ran this motor for a few years and it never had this problem prior to the the pump and pan change.
He found the pump to be in perfect working order and said I am not draining oil back to the pan fast enough and sucking air due to the volume of oil this pump is capable of. That answer surprised me, but I believe him. He is recommending oil restrictors, and doing what I can to ensure oil drain back. I removed the heads to enlarge the drain back holes, removed the valley screens and am seriously considering external drain back lines.

This motor is in a street strip car and may see many miles at hours at a time on the freeway. I have no experience with oil restrictors, or external dran back lines. I see Moroso makes them for the Gen VI Bow Tie motor with a .0625 orifice that can be drilled larger if needed.

I am looking for everyones thoughts on this, and recommendations for the restrictor size and external drains?
Just my .02$.

A pump will pump the maximum it can at a given rpm as it is a positive displacement pump. Always. Most pumps volume vs rpm diagram will show you that it will reach maximum volume at around 1300-1500 rpm. All it will do, when it pumps more volume than the engine needs (which depends on internal clearances) is raise pressure. It will do that until the point when the bypass will open. At that point, all of th excess will be pumped back into the pan. So in principle there is not such thing as sucking the pan dry.

A couple of things could be the problem here:
- incorrect installation of the pump screen versus the pan (not deep enough or too close to the floor of the pan).
- if suction is so strong and the pan has a large surface it could suck up the floor of the pan thereby decreasing the distance to the screen. This can be solved by welding nuts to the screen that prevent the floor from coming too close.
- Incorrect oil level in the pan.
- aeration of the oil due to the crank whipping up the oil and turning it into foam (check if the oil level in the pan is correct and the oil is below the pan baffles.

Long time ago I witnessed a similar problem on mine but it did so at high rpm. The root cause was that I neglected to test the contence of the pan before I mounted it. So I poured in the amount of oil that the manufacturer of the pan said it could contain and I marked the dipstick. I found out that amount of oil would actually make the oil level sit above the baffle of the pan. (courtesy of Kevin Johnson who gave me this advice) I adjusted the oil level to the correct height while measuring the amount of oil. I then remounted the pan, filled it up with the required amount of oil after my test. Remarked the dip stick and never had to look back again.
Your thinking is the same as I thought when it comes to pumps and sucking the pan dry. It was a small twist when I started reading of drain back issues.
The pump and pickup is integral, and matched to the pan depth. I will have to look at my specs but the distance of the pump to pan was a little further than I am use to, it was 1/2 maybe 5/8, I will have to double check to be certain, but again, I do remember it being a little further than what I am use to.
I had a windage issue in my 420 sbc that was solved by removing 1 quart and running 6 quarts instead of 7. That problem showed up at higher rpms. Ever since then I filled my pans up on the bench prior to install to be sure they were not to full. 7 quarts and this pan was full to the tray.
If your pump is sucking the pan fry, you have too many leaks and not enough drainbacks..

Sounds like an oilpan issue. What oil pan are you running?

I run restrictor on many street engines. But I also set all the other clearances inline.

You'd be surprised how much oil can go through an .080" orifice
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Re: BBC oil restrictors

Post by Kevin Johnson »

If air is inadvertently being directed to the pump intake via windage flow then ~9% by volume per Bar pressure can be dissolved and directed through the oil circuits. As the oil pressure lessens and passes the saturation level per Bar pressure, the air will evolve out and create foam. Foam takes time to "break" and release the oil phase. Additionally foam itself flows slowly. Many consumer cleaning products trade on this property.

If the return rate of the oil to the sump does not equal or exceed the volume pumped into the heads/valley, then, yes, it is possible for a pan to be pumped dry or nearly so.

You need to carefully look at the flow patterns in the bottom end and pan.

The pan core that Yves had differed slightly from the one that the design was developed on and this allowed a stream or flow of air into the pickup area. Pan core stampings vary despite looking similar at first glance.


70MC wrote: Tue Jun 30, 2020 1:07 pm I bought a used GM 572 crate motor and changed heads (AFR), cam (solid roller by Jones),lifters (Crower), rocker arms (Crower shaft), oil pump (Titan) and oil pan (Milidon).
I ran the motor with the changes I listed with exception to the oil pump and pan with no problems. I then added the Titan pump and the Milodon pan and immediately had an oil pressure problem. The problem was an oil pressure fluctuation while steady cruising at 55mph, the rpms are around 2500, cant remember exactly. The oil pressure was bouncing from 50-to 60 lbs, and gets worse with rpms.

I sent the pump back to Titan to have inspected since I was sure there was something wrong with it because I ran this motor for a few years and it never had this problem prior to the the pump and pan change.
He found the pump to be in perfect working order and said I am not draining oil back to the pan fast enough and sucking air due to the volume of oil this pump is capable of. That answer surprised me, but I believe him. He is recommending oil restrictors, and doing what I can to ensure oil drain back. I removed the heads to enlarge the drain back holes, removed the valley screens and am seriously considering external drain back lines.

This motor is in a street strip car and may see many miles at hours at a time on the freeway. I have no experience with oil restrictors, or external dran back lines. I see Moroso makes them for the Gen VI Bow Tie motor with a .0625 orifice that can be drilled larger if needed.

I am looking for everyones thoughts on this, and recommendations for the restrictor size and external drains?
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Re: BBC oil restrictors

Post by gnicholson »

Titan makes 2 different volume pumps if I remember for a bbc . Which do you have? Even the std pump puts out a lot of volume compared to a stock pump. 1st thing I would do is verify I had enough pump to pan clearance which I think should be .500. You may be cavitating the pump and sucking air due to that. Honestly you dont need a pump like that for what you are doing. Std m77 with the high pressure spring would work fine
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Re: BBC oil restrictors

Post by af2 »

That pan has nothing to stop the oil from going up the sump and starving the pump. The extra clearance to the pan from the pump is making it worse.
Some kind of kick out is better than none in the sump.
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Re: BBC oil restrictors

Post by Racing68 »

I'm using a canton 13-334 with 10778 melling pump and 10-30 oil in my 505 with no issues. Your pan is very similar to the one i'm using but my pickup is only 5/16 from the bottom of the pan. I've never run one that far from the bottom and that could be the issue.
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Re: BBC oil restrictors

Post by gnicholson »

The reason you have to run the pump that far from the bottom of the pan is the fact that the volume is great enough to cause cavitation if you run it the same height you would a standard volume stock pump. Run a stock style spur gear hv pump 5/16 from the bottom and you will have erratic oil pressure. The titan pump has even more volume. Basically if you run the pump too close to the bottom you dont have enough flow area
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Re: BBC oil restrictors

Post by 70MC »

[quote=mt-engines

If your pump is sucking the pan fry, you have too many leaks and not enough drainbacks..

Sounds like an oilpan issue. What oil pan are you running?

I run restrictor on many street engines. But I also set all the other clearances inline.

You'd be surprised how much oil can go through an .080" orifice
[/quote]

I agree. I am looking for people that run restrictors on the street. In your response, are you saying your restrictor size is .080? If so, did you drill to a size you wanted, and how did you determine the size?
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Re: BBC oil restrictors

Post by 70MC »

Kevin Johnson wrote: Tue Jun 30, 2020 9:24 pm If air is inadvertently being directed to the pump intake via windage flow then ~9% by volume per Bar pressure can be dissolved and directed through the oil circuits. As the oil pressure lessens and passes the saturation level per Bar pressure, the air will evolve out and create foam. Foam takes time to "break" and release the oil phase. Additionally foam itself flows slowly. Many consumer cleaning products trade on this property.

If the return rate of the oil to the sump does not equal or exceed the volume pumped into the heads/valley, then, yes, it is possible for a pan to be pumped dry or nearly so.

You need to carefully look at the flow patterns in the bottom end and pan.

The pan core that Yves had differed slightly from the one that the design was developed on and this allowed a stream or flow of air into the pickup area. Pan core stampings vary despite looking similar at first glance.
I once had a windage problem years ago with my 420sbc, and since then I have tried to read and learn as much as I could here on Spoeedtalk and anywhere else I could find info on oil pans and oil related issues. The 420 was fixed by removing one quart of oil. Since then I always fill my pans prior to install, and I extended the tray in the 420 pan and this 572pan to cover the sump as much as possible and still get the pan on to try to avoid windage blowing oil away from pickup.

With my block being a Gen VI, there are not many pan choices, and fewer than there use to be because some manufacturers stop make pans for the GenVI. This pan does not have a trap door like I am use to seeing in the SBC pans I have used. Milodons answer to there not being a trap door was that there is a baffle at the forward end of the sump that covers the top of the sump to deflect oil back to the sump and toward oil pump. I still wish there was a trap door in it and would love to find one to weld in, but that has proven to be difficult as everyone I called does not sell them.

Can you help with pics of pans that allow the stream of air to the pickup? And do you have any experience with the Milodon pan I am using Milodon 31185? Actually it is the 31186 which has a dipstick provision.
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Re: BBC oil restrictors

Post by 70MC »

gnicholson wrote: Wed Jul 01, 2020 2:55 am Titan makes 2 different volume pumps if I remember for a bbc . Which do you have? Even the std pump puts out a lot of volume compared to a stock pump. 1st thing I would do is verify I had enough pump to pan clearance which I think should be .500. You may be cavitating the pump and sucking air due to that. Honestly you dont need a pump like that for what you are doing. Std m77 with the high pressure spring would work fine
It is the high volume pump, it has the tall gears.
I checked my specs and this pump is 1/2 off the floor of the pan with a gasket.
I never used nothin but stock type pumps and press in pickups since they never gave me an issue. 18 years ago very soon after building a 434sbc the pick up broke off the pump and spun a main bearing. Ever since then I will not use nothing but a pump with an integral pickup. I repaired the 434 and used a Titan pump, I am still using the 434, but it is now in my pickup truck. I do not have an issue with the Titan pump in that motor, that is why I used it in the 572.
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Re: BBC oil restrictors

Post by 70MC »

af2 wrote: Wed Jul 01, 2020 10:22 am That pan has nothing to stop the oil from going up the sump and starving the pump. The extra clearance to the pan from the pump is making it worse.
Some kind of kick out is better than none in the sump.
I wished it had a trap door. Many many years ago I bought a pan for a 350 that had kickouts on the lower sides of the sump to gain oil volume and ground clearance. My machinist said he did not like that style of pan because it gives the oil more places to go instead of surrounding the pickup.
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