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when are 3/4 grooved main bearings needed for bbc ?

General engine tech -- Drag Racing to Circle Track

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ClassAct
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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by ClassAct » Wed Dec 04, 2019 1:44 pm

Kevin Johnson wrote:
Wed Dec 04, 2019 12:47 pm
A SBC and SBM can have the sump reservoir in different locations. Many SBMs have a front sump and during drag racing with a stock type pan it is more likely that the pickup opening will vortex to the surface and/or that the oil displaced to the rear will be churned by the rotating assembly. During vehicle/motor development with parking or driving on grades this will be noted as well. Yes, I know about front sump Chevy II/Nova oil pans.

The additional air that is whipped into the oil by the rotating assembly cannot all be dissolved by the pump so there are free air bubbles present. A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density. This will delay transit in the passage and could require additional degrees of advance to allow for the outer phase (oil) to successfully reach the rod journal. That would be determined by empirical testing under the expected operating conditions. Different companies or even divisions within the same company will generate different solutions.

If you alter the conditions that the vehicle/engine operates under then changes could be needed. Obviously, successful changes have been found by authors in this thread.

You're correct Kevin and I should have mentioned that too. If I am building something that is capable of making 2 HP/CID at 8000 plus it always always gets a rear sump pan or a box pan with the biggest kick out I can get in the car on it.

Also the gerotor pump requires a significantly larger inlet than a spur gear pump. On my best stuff I had a dual pick up with the main pick up at 1 inch and the secondary pick up at number 10 line.

And all that and still it would nick a Rod bearing in 3-4 passes and if you didn't catch it, the 5/6 pass was kicking the Rod out.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by BobbyB » Wed Dec 04, 2019 2:01 pm

Kevin Johnson wrote:
Wed Dec 04, 2019 12:47 pm
A SBC and SBM can have the sump reservoir in different locations. Many SBMs have a front sump and during drag racing with a stock type pan it is more likely that the pickup opening will vortex to the surface and/or that the oil displaced to the rear will be churned by the rotating assembly. During vehicle/motor development with parking or driving on grades this will be noted as well. Yes, I know about front sump Chevy II/Nova oil pans.

The additional air that is whipped into the oil by the rotating assembly cannot all be dissolved by the pump so there are free air bubbles present. A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density. This will delay transit in the passage and could require additional degrees of advance to allow for the outer phase (oil) to successfully reach the rod journal. That would be determined by empirical testing under the expected operating conditions. Different companies or even divisions within the same company will generate different solutions.

If you alter the conditions that the vehicle/engine operates under then changes could be needed. Obviously, successful changes have been found by authors in this thread.
Kevin,

When you say: "A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density", do you mean the oil passage within the crankshaft? Can you expalin more about this? Thanks

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by Kevin Johnson » Wed Dec 04, 2019 3:55 pm

BobbyB wrote:
Wed Dec 04, 2019 2:01 pm
Kevin Johnson wrote:
Wed Dec 04, 2019 12:47 pm
A SBC and SBM can have the sump reservoir in different locations. Many SBMs have a front sump and during drag racing with a stock type pan it is more likely that the pickup opening will vortex to the surface and/or that the oil displaced to the rear will be churned by the rotating assembly. During vehicle/motor development with parking or driving on grades this will be noted as well. Yes, I know about front sump Chevy II/Nova oil pans.

The additional air that is whipped into the oil by the rotating assembly cannot all be dissolved by the pump so there are free air bubbles present. A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density. This will delay transit in the passage and could require additional degrees of advance to allow for the outer phase (oil) to successfully reach the rod journal. That would be determined by empirical testing under the expected operating conditions. Different companies or even divisions within the same company will generate different solutions.

If you alter the conditions that the vehicle/engine operates under then changes could be needed. Obviously, successful changes have been found by authors in this thread.
Kevin,

When you say: "A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density", do you mean the oil passage within the crankshaft? Can you expalin more about this? Thanks
To simplify things, just think about the passage past the centerline of the crankshaft. There are different possible drillings that can create more or less drama to that point, of course.

The wall of the passage is rotating about the central (longitudinal) axis of the crankshaft and so a vector component of the centripetal reaction force will accelerate the airbubble-in-oil mixture towards the rod journal. The inner phase is air (bubbles) and the outer phase is oil. The higher density of the oil will force any bubbles at the end of the passage back and this will interfere with the transit of more oil (and bubbles) to that area. Hopefully the smaller bubbles will not coalesce into larger ones by their forced proximity.

Here is a free full text paper that explores the wonderful complexity of a related problem; there are numerous papers on the topic in general: https://www.researchgate.net/publicatio ... ating_flow There are also numerous patents for deaerators based on this action. Laboratory centrifuges will stratify samples by relative density.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by BobbyB » Wed Dec 04, 2019 6:58 pm

Kevin Johnson wrote:
Wed Dec 04, 2019 3:55 pm
BobbyB wrote:
Wed Dec 04, 2019 2:01 pm
Kevin Johnson wrote:
Wed Dec 04, 2019 12:47 pm
A SBC and SBM can have the sump reservoir in different locations. Many SBMs have a front sump and during drag racing with a stock type pan it is more likely that the pickup opening will vortex to the surface and/or that the oil displaced to the rear will be churned by the rotating assembly. During vehicle/motor development with parking or driving on grades this will be noted as well. Yes, I know about front sump Chevy II/Nova oil pans.

The additional air that is whipped into the oil by the rotating assembly cannot all be dissolved by the pump so there are free air bubbles present. A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density. This will delay transit in the passage and could require additional degrees of advance to allow for the outer phase (oil) to successfully reach the rod journal. That would be determined by empirical testing under the expected operating conditions. Different companies or even divisions within the same company will generate different solutions.

If you alter the conditions that the vehicle/engine operates under then changes could be needed. Obviously, successful changes have been found by authors in this thread.
Kevin,

When you say: "A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density", do you mean the oil passage within the crankshaft? Can you expalin more about this? Thanks
To simplify things, just think about the passage past the centerline of the crankshaft. There are different possible drillings that can create more or less drama to that point, of course.

The wall of the passage is rotating about the central (longitudinal) axis of the crankshaft and so a vector component of the centripetal reaction force will accelerate the airbubble-in-oil mixture towards the rod journal. The inner phase is air (bubbles) and the outer phase is oil. The higher density of the oil will force any bubbles at the end of the passage back and this will interfere with the transit of more oil (and bubbles) to that area. Hopefully the smaller bubbles will not coalesce into larger ones by their forced proximity.

Here is a free full text paper that explores the wonderful complexity of a related problem; there are numerous papers on the topic in general: https://www.researchgate.net/publicatio ... ating_flow There are also numerous patents for deaerators based on this action. Laboratory centrifuges will stratify samples by relative density.
Thanks Kevin. There is deep stuff in that paper.
My understanding is that very much air in the oil will destroy the bearings if the bearing loads are very high. Is that correct?

However, very little or nothing can be done to the bearings or crankshaft to make them live with much air trapped in the oil. Is that correct?

So, we must take measures to stop air from getting trapped in the oil before it goes to the crankshaft. Correct?

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by Kevin Johnson » Wed Dec 04, 2019 7:21 pm

BobbyB wrote:
Wed Dec 04, 2019 6:58 pm
Kevin Johnson wrote:
Wed Dec 04, 2019 3:55 pm
BobbyB wrote:
Wed Dec 04, 2019 2:01 pm


Kevin,

When you say: "A bubble filled fluid being accelerated by the oil passage will have conflicting phase flow paths determined by density", do you mean the oil passage within the crankshaft? Can you expalin more about this? Thanks
To simplify things, just think about the passage past the centerline of the crankshaft. There are different possible drillings that can create more or less drama to that point, of course.

The wall of the passage is rotating about the central (longitudinal) axis of the crankshaft and so a vector component of the centripetal reaction force will accelerate the airbubble-in-oil mixture towards the rod journal. The inner phase is air (bubbles) and the outer phase is oil. The higher density of the oil will force any bubbles at the end of the passage back and this will interfere with the transit of more oil (and bubbles) to that area. Hopefully the smaller bubbles will not coalesce into larger ones by their forced proximity.

Here is a free full text paper that explores the wonderful complexity of a related problem; there are numerous papers on the topic in general: https://www.researchgate.net/publicatio ... ating_flow There are also numerous patents for deaerators based on this action. Laboratory centrifuges will stratify samples by relative density.
Thanks Kevin. There is deep stuff in that paper.
My understanding is that very much air in the oil will destroy the bearings if the bearing loads are very high. Is that correct?

However, very little or nothing can be done to the bearings or crankshaft to make them live with much air trapped in the oil. Is that correct?

So, we must take measures to stop air from getting trapped in the oil before it goes to the crankshaft. Correct?
I believe damage occurs in rod bearings at 30% (might be lower) and mains at 50%.

The big issue is free air -- dissolved air levels can be quite high (about 9% by volume per bar). However, for an oil pump to accomplish this the oil bubbles need to be small. https://www.sae.org/publications/techni ... 4-01-2915/

Once dissolved air goes through a pressure drop in or external to a circuit, any supersaturation will resolve by the prompt formation of copious amounts of foam. This can quite a problem as well.

Yes, the key idea is to hinder the air getting into the oil in the first place.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by BobbyB » Wed Dec 04, 2019 7:37 pm

Kevin Johnson wrote:
Wed Dec 04, 2019 7:21 pm
BobbyB wrote:
Wed Dec 04, 2019 6:58 pm
Kevin Johnson wrote:
Wed Dec 04, 2019 3:55 pm


To simplify things, just think about the passage past the centerline of the crankshaft. There are different possible drillings that can create more or less drama to that point, of course.

The wall of the passage is rotating about the central (longitudinal) axis of the crankshaft and so a vector component of the centripetal reaction force will accelerate the airbubble-in-oil mixture towards the rod journal. The inner phase is air (bubbles) and the outer phase is oil. The higher density of the oil will force any bubbles at the end of the passage back and this will interfere with the transit of more oil (and bubbles) to that area. Hopefully the smaller bubbles will not coalesce into larger ones by their forced proximity.

Here is a free full text paper that explores the wonderful complexity of a related problem; there are numerous papers on the topic in general: https://www.researchgate.net/publicatio ... ating_flow There are also numerous patents for deaerators based on this action. Laboratory centrifuges will stratify samples by relative density.
Thanks Kevin. There is deep stuff in that paper.
My understanding is that very much air in the oil will destroy the bearings if the bearing loads are very high. Is that correct?

However, very little or nothing can be done to the bearings or crankshaft to make them live with much air trapped in the oil. Is that correct?

So, we must take measures to stop air from getting trapped in the oil before it goes to the crankshaft. Correct?
I believe damage occurs in rod bearings at 30% (might be lower) and mains at 50%.

The big issue is free air -- dissolved air levels can be quite high (about 9% by volume per bar). However, for an oil pump to accomplish this the oil bubbles need to be small. https://www.sae.org/publications/techni ... 4-01-2915/

Once dissolved air goes through a pressure drop in or external to a circuit, any supersaturation will resolve by the prompt formation of copious amounts of foam. This can quite a problem as well.

Yes, the key idea is to hinder the air getting into the oil in the first place.
Thanks very much Kevin.

So, what are the main reasons that air gets in the oil on:

A 5000 rpm factory v8 from the 1970s?

The same v8 hot rodded to turn 6500 rpm on the street?

The same v8 modded to turn 7500 rpm on the drag strip?

The same v8 modded for 7500 on a road course?

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by cjperformance » Wed Dec 04, 2019 9:02 pm

A few notes to throw in the mix,

Oil viscosity, the higher the viscosity the harder it is to seperate the air. So once the correct viscosity is decided upon you need to keep oil up to the correct temp, cooler oil = more air.

Drain back, obviously as oil drains back to the pan you want its return path to help seperate oil, not pass the oil over rotating components to help get air in the oil!

Baffling, is not only good for stopping oil slosh but also helpful to allow the oil an area to run over before the oil enters the sump which gives more time for air to escape.

Pressure , the higher the oil pressure , the more air you can keep held in solution, this air then escapes as the pressure suddenly drops, ie- entering a bearing.
So focus on oil delivery via quality/quantity, by means of efficient delivery/fittings/galleries etc not by means of jacking up the pressure.
Craig.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by Warp Speed » Thu Dec 05, 2019 4:58 am

ClassAct wrote:
Wed Dec 04, 2019 11:53 am
Warp Speed wrote:
Wed Dec 04, 2019 4:47 am
ClassAct wrote:
Tue Dec 03, 2019 9:49 pm



You are still wrong. Figure I out warp. The lifters don't matter. I can block the oil to the lifters and it STILL doesn't fix the issue.

Damn you are stubborn.
Damn you are clueless! :lol:
Maybe you should try a different hobby?

I will ask AGAIN, why doesn't a 351w have the same problem as a 351c, when they have the same "block timing" that you preach is the root of all evil?!?
I mean neither is an optimum design, but why?!?


Post up the oil schematic for both. You keep going back to that and I keep asking why does the SBC oil when others don't. And you say it's the third oil gallery. I say it's not, because it isn't. And again, for all those who are having trouble getting the concept down, nowhere have I said, not a SINGLE TIME have I said that priority main oiling wasn't the way to do it. I've said priority main oiling doesn't fix a Rod bearing oiling issue. That's pretty simple and self evident.

You tell me how can the main bearings look brand new and the Rod bearing are BLUE? The oil is at the main bearing. Has to be. Or they'd be blue as well. It's because at some point, at some RPM/load, bearing diameter, oil hole clocking, the Rod bearing won't get enough oil at the correct TIME. Period. Priority main oiling doesn't fix this. Bushing the lifter bores will help, just like a full groove main, but the point will come when even those things aren't enough.

This isn't hard.

Like I said for all the doubters just grab a SBM block and crank and a SBC block and crank and get out your degree wheel. Look at the oil feed hole in the main bearing. It will be the same on both cranks. Exactly the same. Then look at the oil feed holes in both blocks. You'll quickly see that the SBC is at 12 o'clock and the SBM is about 11 o'clock.

Put the crank in the SBC and mark on the crank where the oil feed hole is. Mount your degree wheel and see when the hole in the block lines up with the hole in the crank on the SBC. The piston will be ~ 70* ATDC. Warp says 90 but my memory says 70.

Either way, do the same on the SBM and you'll see the oil gets to the rods on the SBM way too early. IIRC it's about 58 or so degrees ATDC, but it's been a while since I checked one. That means the SBM is advanced by roughly 12 degrees.

And before all the naysayers and nattering nabobs say it's only 12 degrees...that ain't shit, run out and add 12 degrees total to your engine and then go out and throw a load on it and see how long it lasts.

That's why bushing the lifter bores HELPS. Doesn't fix it, but it delays the RPM/load at which oil starvation occurs. Just like a full groove main bearing. You are getting SOME oil to the rods all the time. But again, at some RPM/load that won't be enough. And the Rod bearings don't get ENOUGH oil at the correct TIME and then it's all over.

So yes, 10-12 degrees of oil timing matters.
Against my better judgment, I will answer you one more time. Rick posted both the 351c, and the 351w schematics earlier, and you actually quoted it above. The only difference is quite obvious, and its not a change in "block timing"!
But back to your sbc timing deal, you say a sbc gets oiled at the "correct time", what cylinder are you referring to?
Most all domestic 90* v8 engines, have the same crank drillings/timing (straight drilling), so again, why doesnt the 351w have problems due to this "early timing" phenomenon?

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by tenxal » Thu Dec 05, 2019 7:40 am

BobbyB wrote:
Wed Dec 04, 2019 6:28 am
Isn’t all this stuff just branch circuits in a simple hydraulic system...just one pump...right?
No. Even the simplest hydraulic system is a 'closed' system. An engine oil system is one big leak. Oil leakage around the lifters has a much bigger impact than most realize.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by swampbuggy » Thu Dec 05, 2019 8:04 am

BobbyB: I will take a shot at your 2 questions from above. What is quality oiling? 1. Enough quality oil in the reservoir ( be it wet sump or dry sump) so that the oil pump never draws air. 2. Minimizing the amount of air introduced into the oil by proper oil pan design, baffling etc. . 3. Separating the air from the aerated oil in the system (this is an area where a dry-sump system shines) 4. Provide adequate pressure without being excessive. 5. Keeping the oil at an acceptable temperature. 6. A well designed engine block to route the oil properly :shock: What happens if a lifter exits it's hole? It would depend on how the engine block was (is) designed, but on thing for sure if the block was not designed to send oil to the mains first the results are gonna be worse. Mark H.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by tenxal » Thu Dec 05, 2019 8:19 am

ClassAct wrote:
Wed Dec 04, 2019 1:44 pm
On my best stuff I had a dual pick up with the main pick up at 1 inch and the secondary pick up at number 10 line. And all that and still it would nick a Rod bearing in 3-4 passes and if you didn't catch it, the 5/6 pass was kicking the Rod out.
Something is very, very wrong........ :shock:

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by ClassAct » Thu Dec 05, 2019 11:07 am

tenxal wrote:
Thu Dec 05, 2019 8:19 am
ClassAct wrote:
Wed Dec 04, 2019 1:44 pm
On my best stuff I had a dual pick up with the main pick up at 1 inch and the secondary pick up at number 10 line. And all that and still it would nick a Rod bearing in 3-4 passes and if you didn't catch it, the 5/6 pass was kicking the Rod out.
Something is very, very wrong........ :shock:


Exactly. Very wrong. Like the oil timing is off.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by BobbyB » Thu Dec 05, 2019 2:02 pm

tenxal wrote:
Thu Dec 05, 2019 7:40 am
BobbyB wrote:
Wed Dec 04, 2019 6:28 am
Isn’t all this stuff just branch circuits in a simple hydraulic system...just one pump...right?
No. Even the simplest hydraulic system is a 'closed' system. An engine oil system is one big leak. Oil leakage around the lifters has a much bigger impact than most realize.
Thanks Tenxal,

Is it safe to say that an engine is actually a specific number of (hopefully) very accurate leaks? Including every bearing, lifter bore to lifter clearance, ect... and if any ONE of them leaks more than expected ALL the others get less flow that originally expected?

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by BobbyB » Thu Dec 05, 2019 2:08 pm

swampbuggy wrote:
Thu Dec 05, 2019 8:04 am
BobbyB: I will take a shot at your 2 questions from above. What is quality oiling? 1. Enough quality oil in the reservoir ( be it wet sump or dry sump) so that the oil pump never draws air. 2. Minimizing the amount of air introduced into the oil by proper oil pan design, baffling etc. . 3. Separating the air from the aerated oil in the system (this is an area where a dry-sump system shines) 4. Provide adequate pressure without being excessive. 5. Keeping the oil at an acceptable temperature. 6. A well designed engine block to route the oil properly :shock: What happens if a lifter exits it's hole? It would depend on how the engine block was (is) designed, but on thing for sure if the block was not designed to send oil to the mains first the results are gonna be worse. Mark H.
Thanks very much swampbuggy,

Can you tell me where you have seen a well designed block, with oil to mains first, develop a big internal leak (say a lifter blows out) and not destroy the engine completely? Does it really make that much difference if something goes bad?

For example, will a 351W really only destroy $500 worth of good parts if a pushrod breaks, where as a 351C will destroy the whole engine if a pushrod breaks?

Just trying to understand how much difference there is when things go wrong.

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Re: when are 3/4 grooved main bearings needed for bbc ?

Post by ClassAct » Thu Dec 05, 2019 6:22 pm

tenxal wrote:
Thu Dec 05, 2019 7:40 am
BobbyB wrote:
Wed Dec 04, 2019 6:28 am
Isn’t all this stuff just branch circuits in a simple hydraulic system...just one pump...right?
No. Even the simplest hydraulic system is a 'closed' system. An engine oil system is one big leak. Oil leakage around the lifters has a much bigger impact than most realize.

Right. And the leaks around the lifters is a relatively simple fix.

It's a simple hydraulic system. Not uncontrolled leaks. That's crazy to claim that.

I had a joker call me today and claim you can fix this junk with a dry sump. I said how so? And this dude (a self proclaimed expert) says you're sucking the pan dry. I say...ok thanks...goodbye.


I have a minimum of 10 quarts in the system on the dyno. And this guy thinks the pan is empty on a dyno pull. Rediculous.


Call around. Find someone who knows this stuff...like someone who does a lot of viper stuff and call and ask them about oil timing. They sure as shit know what it is. And have ways to get around it. Until you need to correct it.

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