How long does it take the oil to drain back to the pan in a BB?
01-30-2003, 11:04 PM
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How long does it take the oil to drain back to the pan in a BB?
Even though the engine has yet to be pulled and torn down, the consensus thus for what went wrong with my engine is that I drained the pan after several quick high RPM runs in a row and starved one or more of the bearings.
I have had 4-5 engine builders and mechanics tell me that this is what probably happened and that it is quite common in BB's.
I believe them, but I just do not understand this. If this in fact is what caused my problem, I do not know how people are not doing this all the time. I did run it hard through the gears several times right in a row, but nothing that should have caused all of the oil to be pumped from the pan.
What gives here?
I have had 4-5 engine builders and mechanics tell me that this is what probably happened and that it is quite common in BB's.
I believe them, but I just do not understand this. If this in fact is what caused my problem, I do not know how people are not doing this all the time. I did run it hard through the gears several times right in a row, but nothing that should have caused all of the oil to be pumped from the pan.
What gives here?
01-31-2003, 05:26 AM
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Re: How long does it take the oil to drain back to the pan in a BB? (hudman)
Hmm... Were you using a high-volume or stock pump? Was the casting flash removed from the oil drain back holes in the heads and block? Windage tray used?
With a stock 6-qt pan and pump, it is highly unlikely that all the oil was trapped 'up top', and is not common for BBCs. In fact, BBCs are known for their bulletproof lubrication system, especially in the bottom end. Seems further investigation is required.
Do you still have the pump? Did the driveshaft coupling fail? What pressures were you seeing in regular driving? Maybe the gear end-gap was excessive, or the relief valve failed. Was the pickup set at the correct height? Did the pickup fall off?
There is a chance it could be a combination of loose bearing tolerances, high flow pump, and low oil level, as I have heard stories like that before. Reason enough for me to not use a high-volume pump on my rebuild.
Too me, it seems somewhat presumptuous for a mechanic to make that claim without explaining the details of their investigation.
With a stock 6-qt pan and pump, it is highly unlikely that all the oil was trapped 'up top', and is not common for BBCs. In fact, BBCs are known for their bulletproof lubrication system, especially in the bottom end. Seems further investigation is required.
Do you still have the pump? Did the driveshaft coupling fail? What pressures were you seeing in regular driving? Maybe the gear end-gap was excessive, or the relief valve failed. Was the pickup set at the correct height? Did the pickup fall off?
There is a chance it could be a combination of loose bearing tolerances, high flow pump, and low oil level, as I have heard stories like that before. Reason enough for me to not use a high-volume pump on my rebuild.
Too me, it seems somewhat presumptuous for a mechanic to make that claim without explaining the details of their investigation.
01-31-2003, 08:54 AM
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Re: How long does it take the oil to drain back to the pan in a BB? (Turbo-Jet)
...Too me, it seems somewhat presumptuous for a mechanic to make that claim without explaining the details of their investigation.
02-01-2003, 09:03 AM
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Re: How long does it take the oil to drain back to the pan in a BB? (hudman)
I have a bigblock with a High volumn pump, a six quart oil pan, windage tray , and pickup set about 3/8th of an inch off the bottom . I also have a warning light set at 50 lbs oil pressure. I normally run about 70 pounds with the hot idle just flickering the light.
On hard launch the light does come on showing me I ave a problem with the oil either running away from the pickup on hard launch or the pump is pumping the sump dry. This happens quit often and bothers me. If I overfill the sump a little it stops the light from comming on.
With the warning light I would never know this is happening.
It is possible the mechanic is right and you are starving the motor at the most critical time.
Have you ever seen the stock cars on a small tight track. Alot of oil pressure warning lights come on in the corners. They are momentarily loosing oil pressure on the hard turns but it is at the time when the motor is not under load so they survive. I have a friend in CANSCAR with very high dollar motors and he said they are not hurt at that moment due to this unloading of power.
On hard launch the light does come on showing me I ave a problem with the oil either running away from the pickup on hard launch or the pump is pumping the sump dry. This happens quit often and bothers me. If I overfill the sump a little it stops the light from comming on.
With the warning light I would never know this is happening.
It is possible the mechanic is right and you are starving the motor at the most critical time.
Have you ever seen the stock cars on a small tight track. Alot of oil pressure warning lights come on in the corners. They are momentarily loosing oil pressure on the hard turns but it is at the time when the motor is not under load so they survive. I have a friend in CANSCAR with very high dollar motors and he said they are not hurt at that moment due to this unloading of power.
02-01-2003, 10:48 AM
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Re: How long does it take the oil to drain back to the pan in a BB? (norvalwilhelm)
These are reputable guys that are telling me this and I am hearing this from multiple sources.
One guy said he starved a bearing when his car was a half a quart of oil low.
I thought I had plenty of oil in mine, but I guess I was wrong. I need to check that. It is still in driveway now.
Another guy said that if you are going to the track or planning to drive it hard, put an extra half quart or so in there and that it would keep it from happening.
I guess this is much more likely to happen to a motor with some mileage and wear and tear on it vs. a freshly rebuilt one. Looks like a rebuild for me.
One guy said he starved a bearing when his car was a half a quart of oil low.
I thought I had plenty of oil in mine, but I guess I was wrong. I need to check that. It is still in driveway now.
Another guy said that if you are going to the track or planning to drive it hard, put an extra half quart or so in there and that it would keep it from happening.
I guess this is much more likely to happen to a motor with some mileage and wear and tear on it vs. a freshly rebuilt one. Looks like a rebuild for me.
02-01-2003, 01:51 PM
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Re: How long does it take the oil to drain back to the pan in a BB? (hudman)
I agree with the extra 1/2 quart. That is what I do if I am going to push the motor. I don't agree that just because the motor has some miles on it that it is more likely to happen.
Now a big bearing burner. Cold engines. I have spun a few bearings by taking a car out and about a mile out of town stopping and letting it go. Happened to me twice. I learned my leason. Until I see the idle oil pressure starting to dop and I know the oil and motor are warmed up I will NOT push it. Dropping in for gas just 1/4 mile from my place the owner will ask me to just give it a little chew. I always refuse but on returning home I might stop in and give it a little bite.
Cold motors spin bearings.
Now a big bearing burner. Cold engines. I have spun a few bearings by taking a car out and about a mile out of town stopping and letting it go. Happened to me twice. I learned my leason. Until I see the idle oil pressure starting to dop and I know the oil and motor are warmed up I will NOT push it. Dropping in for gas just 1/4 mile from my place the owner will ask me to just give it a little chew. I always refuse but on returning home I might stop in and give it a little bite.
Cold motors spin bearings.
02-01-2003, 03:41 PM
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Re: How long does it take the oil to drain back to the pan in a BB? (hudman)
hudman,
If you look in the book "a guide to Corvette speed" by Karl Ludvigsen it talks about this problem and shows pics of a BB race engine with drain tubes from the valve cover back to the pan. I think there are several ways to restrict the oil flow to the top end. ...redvetracr
If you look in the book "a guide to Corvette speed" by Karl Ludvigsen it talks about this problem and shows pics of a BB race engine with drain tubes from the valve cover back to the pan. I think there are several ways to restrict the oil flow to the top end. ...redvetracr
02-01-2003, 04:47 PM
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Re: How long does it take the oil to drain back to the pan in a BB? (redvetracr)
Norval-
I think you may be on to something with the cold engine theory. I had driven the car to a rally that was 40-50 miles out of town. It was like 20 degrees or something. Very very cold. When we got there, the car sat for 45min or 1 hr. It was plenty of time to cool back down given the cold temp and the high wind chill. I probably did not give it enough time to fully warm up. I am usually very cautious about driving it hard until it is warmed up. I thought I would be OK given that it had been operating for 1 hr or more shortly before we got going.
I cranked it up 2-3 minutes before we actually left for the rally. Once we started, I jumped on it a few times during the first 5 minutes of the rally. And then the disaster. I guess it could be the cold temp???
I think you may be on to something with the cold engine theory. I had driven the car to a rally that was 40-50 miles out of town. It was like 20 degrees or something. Very very cold. When we got there, the car sat for 45min or 1 hr. It was plenty of time to cool back down given the cold temp and the high wind chill. I probably did not give it enough time to fully warm up. I am usually very cautious about driving it hard until it is warmed up. I thought I would be OK given that it had been operating for 1 hr or more shortly before we got going.
I cranked it up 2-3 minutes before we actually left for the rally. Once we started, I jumped on it a few times during the first 5 minutes of the rally. And then the disaster. I guess it could be the cold temp???
