once after repairing the oil pan I added half a quart to the empty engine and started her up. OIl light went out, no nasty noises etc, but the car wasn't moved. 6 quart sump, 5 cilinder engine.
Volume of oil in circulation in engine...
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Originally Posted By: MolaKule
Originally Posted By: Dallas69
Why do trucks and some cars have sumps over 6 qts if less than 2 qts are in use at any given time?
It's called sump, "dwell time." The more oil mass you have in the sump means more of the oil mass will get more time to cool.
Yeah, this. Allowing the oil to rest in the sump also allows it to release more of its entrained air that it got when it was being thrashed around by the engine machinery. Decreasing the recirculation rate increases the life of the oil.
Large quantities of oil can reside in the crankcase at high rpm because it is being whipped up by the crank and rods. A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Originally Posted By: Dallas69
Why do trucks and some cars have sumps over 6 qts if less than 2 qts are in use at any given time?
It's called sump, "dwell time." The more oil mass you have in the sump means more of the oil mass will get more time to cool.
Yeah, this. Allowing the oil to rest in the sump also allows it to release more of its entrained air that it got when it was being thrashed around by the engine machinery. Decreasing the recirculation rate increases the life of the oil.
Large quantities of oil can reside in the crankcase at high rpm because it is being whipped up by the crank and rods. A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Originally Posted By: A_Harman".........
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
I disagree in part.
If the engine is blowing by excessively, there will be a gasflow from crankcase to valve train in direction....on the whole, gravity will still win.
Although a guy I used to knock around with found that a stone cold, 7,000RPM burnout on his well worn Isuzu twin cam, he could cause loss of oil pressure due to oil not getting back there.
If the engine is blowing by excessively, there will be a gasflow from crankcase to valve train in direction....on the whole, gravity will still win.
Although a guy I used to knock around with found that a stone cold, 7,000RPM burnout on his well worn Isuzu twin cam, he could cause loss of oil pressure due to oil not getting back there.
Originally Posted By: Shannow
I disagree in part.
If the engine is blowing by excessively, there will be a gasflow from crankcase to valve train in direction....on the whole, gravity will still win……."
you've got a valid point on the blowby, as far as air turbulence is concerned, but the actual pressure will equalize because we are not talking about a huge volume as space here, the actual air space in internal combustion engines is really very small. Manufacturers don't like to spent $$$ on big castings when they can be made smaller, and cheaper, by using less metal.
but in a healthy engine, the blow-by should be of little consequence.
Z
I disagree in part.
If the engine is blowing by excessively, there will be a gasflow from crankcase to valve train in direction....on the whole, gravity will still win……."
you've got a valid point on the blowby, as far as air turbulence is concerned, but the actual pressure will equalize because we are not talking about a huge volume as space here, the actual air space in internal combustion engines is really very small. Manufacturers don't like to spent $$$ on big castings when they can be made smaller, and cheaper, by using less metal.
but in a healthy engine, the blow-by should be of little consequence.
Z
Last edited:
Originally Posted By: Shannow
I disagree in part.
If the engine is blowing by excessively, there will be a gasflow from crankcase to valve train in direction....on the whole, gravity will still win.
Although a guy I used to knock around with found that a stone cold, 7,000RPM burnout on his well worn Isuzu twin cam, he could cause loss of oil pressure due to oil not getting back there.
Yes,the oil gets pumped faster than gravity allows the oil to return to the sump.
I disagree in part.
If the engine is blowing by excessively, there will be a gasflow from crankcase to valve train in direction....on the whole, gravity will still win.
Although a guy I used to knock around with found that a stone cold, 7,000RPM burnout on his well worn Isuzu twin cam, he could cause loss of oil pressure due to oil not getting back there.
Yes,the oil gets pumped faster than gravity allows the oil to return to the sump.
Originally Posted By: CT8
".......Yes,the oil gets pumped faster than gravity allows the oil to return to the sump.
This is about as close to a myth as you can get, without actually being a myth. Yes it can happen, but it is going to happen on engines that have been modified to run at nearly double the manufacturers intended rom range. And any engine builder worth his salt who is building these high revving engines will modify the oil galleys to restrict flow to the top end as standard practice. Only a novice is going to make the mistake of not doing so. On a street engine, or street hot rod, there is never going to be a crankcase that is pumped dry because the oil isn't comig back to the sump fast enough. Oil pump pressure issues at high rpm are almost always caused by excessive bearing clearances, a plugged up or old screen on the pick up, or a crack in the pick up tube.
Z
".......Yes,the oil gets pumped faster than gravity allows the oil to return to the sump.
This is about as close to a myth as you can get, without actually being a myth. Yes it can happen, but it is going to happen on engines that have been modified to run at nearly double the manufacturers intended rom range. And any engine builder worth his salt who is building these high revving engines will modify the oil galleys to restrict flow to the top end as standard practice. Only a novice is going to make the mistake of not doing so. On a street engine, or street hot rod, there is never going to be a crankcase that is pumped dry because the oil isn't comig back to the sump fast enough. Oil pump pressure issues at high rpm are almost always caused by excessive bearing clearances, a plugged up or old screen on the pick up, or a crack in the pick up tube.
Z
Originally Posted By: zray
Originally Posted By: A_Harman".........
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
It doesn't take much crankcase pressure to keep oil draining from the cylinder heads. If there is 3" H20 pressure in the crankcase, that is enough to hold more than 3" of oil depth in the cylinder heads.
Originally Posted By: A_Harman".........
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
It doesn't take much crankcase pressure to keep oil draining from the cylinder heads. If there is 3" H20 pressure in the crankcase, that is enough to hold more than 3" of oil depth in the cylinder heads.
Originally Posted By: Chris142
A 454 holds 5 qts but grannnies northstar holds 8
Wife's 3.6L Pentastar has a 6-quart capacity, and my SRT has a 7-quart capacity. Manufacturers are waking up to the advantages of bigger sumps, longer sump dwell time, larger safety margin when people go 10,000 miles without even pulling the dipstick, etc.
A 454 holds 5 qts but grannnies northstar holds 8
Wife's 3.6L Pentastar has a 6-quart capacity, and my SRT has a 7-quart capacity. Manufacturers are waking up to the advantages of bigger sumps, longer sump dwell time, larger safety margin when people go 10,000 miles without even pulling the dipstick, etc.
Originally Posted By: A_Harman
Originally Posted By: zray
Originally Posted By: A_Harman".........
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
It doesn't take much crankcase pressure to keep oil draining from the cylinder heads. If there is 3" H20 pressure in the crankcase, that is enough to hold more than 3" of oil depth in the cylinder heads.
But the return holes are HUGE compared to the oil supply galleries, at least on most engines. There's no way that a solid "plug" of oil could form in even one of the 1/2" tall by 4" wide drainback passages in a big-block Chrysler, let alone all 8 (4 on each cylinder head).
Originally Posted By: zray
Originally Posted By: A_Harman".........
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
It doesn't take much crankcase pressure to keep oil draining from the cylinder heads. If there is 3" H20 pressure in the crankcase, that is enough to hold more than 3" of oil depth in the cylinder heads.
But the return holes are HUGE compared to the oil supply galleries, at least on most engines. There's no way that a solid "plug" of oil could form in even one of the 1/2" tall by 4" wide drainback passages in a big-block Chrysler, let alone all 8 (4 on each cylinder head).
Originally Posted By: 440Magnum
Originally Posted By: A_Harman
Originally Posted By: zray
Originally Posted By: A_Harman".........
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
It doesn't take much crankcase pressure to keep oil draining from the cylinder heads. If there is 3" H20 pressure in the crankcase, that is enough to hold more than 3" of oil depth in the cylinder heads.
But the return holes are HUGE compared to the oil supply galleries, at least on most engines. There's no way that a solid "plug" of oil could form in even one of the 1/2" tall by 4" wide drainback passages in a big-block Chrysler, let alone all 8 (4 on each cylinder head).
thank you.
The folks at Melling will tell you that even their high volume pump cannot, and will not, pump the oil pan dry. But people hardly ever listen to facts in this world. They just keep believing what they want to believe.
technically speaking, it's koo-koo.
z
Originally Posted By: A_Harman
Originally Posted By: zray
Originally Posted By: A_Harman".........
A lot of oil also can stay in the cylinder head valve boxes if crankcase pressure is too high to allow it to drain.
Now there certainly can be a lot of oil the heads, as it is getting pumped up there, but to say the crankcase pressure is, or could be, holding it up there is not true. The pressure under valve covers or lifter valley, is going to be identical to the pressure down under the crankshaft. There is nothing holding the pressure down below. It is all equalized thru out the engine.
Z
It doesn't take much crankcase pressure to keep oil draining from the cylinder heads. If there is 3" H20 pressure in the crankcase, that is enough to hold more than 3" of oil depth in the cylinder heads.
But the return holes are HUGE compared to the oil supply galleries, at least on most engines. There's no way that a solid "plug" of oil could form in even one of the 1/2" tall by 4" wide drainback passages in a big-block Chrysler, let alone all 8 (4 on each cylinder head).
thank you.
The folks at Melling will tell you that even their high volume pump cannot, and will not, pump the oil pan dry. But people hardly ever listen to facts in this world. They just keep believing what they want to believe.
technically speaking, it's koo-koo.
z
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