Home » Public Forums » GMCnet » [GMCnet] What turns engine oil black?
| [GMCnet] What turns engine oil black? [message #245791] |
Sun, 30 March 2014 16:37  |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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G'day,
KenH mentioned that his engine oil stayed clear for his foray to Montgomery and back; he attributed that to a clean, newly rebuilt
engine with fresh oil and a lack of contaminants in the oil.
I'm not disagreeing with Ken but somewhere deep in the bowels of my memory I seem to remember someone telling me or reading
something that said heat turned the oil black.
Obviously Ken's trip was not long enough to do that to his oil so does heat have an effect on engine oil color?
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] What turns engine oil black? [message #245801 is a reply to message #245791] |
Sun, 30 March 2014 18:42  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Rob,
I, too, was a little surprised that the oil didn't darken from carbon
collection
but cleared up, apparently from iron filtration. I certainly expect the
oil to turn black when I've got 4-5000 miles on it, but this 1600+ mile
trip was run at a consistent 196*F-198*F H20 temperature with oil temp
consistently near 220*F. That cool run, plus EFI, probably helped prevent
darkening. My real surprise was that it looked better after than before
the run.
Ken H.
On Sun, Mar 30, 2014 at 4:37 PM, Robert Mueller wrote:
> KenH mentioned that his engine oil stayed clear for his foray to
> Montgomery and back; he attributed that to a clean, newly rebuilt
> engine with fresh oil and a lack of contaminants in the oil.
>
> I'm not disagreeing with Ken but somewhere deep in the bowels of my
> memory I seem to remember someone telling me or reading
> something that said heat turned the oil black.
>
> Obviously Ken's trip was not long enough to do that to his oil so does
> heat have an effect on engine oil color?
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] What turns engine oil black? [message #245822 is a reply to message #245813] |
Sun, 30 March 2014 20:57 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
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| BobDunahugh wrote on Sun, 30 March 2014 18:26 |
Why Rob. Black stuff does it. ( GRIN ) When I take any of my COPO Yenko Stingers road racing for a day or two. When I get home. The first thing I do is change my engine oil, and brake fluid. The brake fluid gets cooked due to the extreme temperatures. The engine temps generally stay under 200. I generally put about 300 miles on at around 6,000 to 7,500 RPM's So for the engine. The oil isn't that used. I'm just look shiney stuff in the oil,and filter material. One thing I have noticed is in the engines that have the gapless piston rings. The oil is always cleaner than the engine that has piston rings with end gap clearance. So to me. The darkening of the oil is mostly due to the blow by from combustion. I run 110 octane leaded fuel. I need as cold a burning fuel as I can get. As I have a compression ratio of about 13 to i. 87 octane fuel is too hot a fuel to run. So both types of rings are subjected to the same loads. When running a compression test. The gapless rings will
be at around 200lbs. The gaped rings will be at 160lbs. So guess what's getting to the oil. Black stuff.Bob Dunahugh
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Going by that theory I would suspect an engine with forged pistons would have darker oil then cast pistons because there is more piston clearance needed with forged pistons. The Molly rings never seated properly in my 455 olds boat engine so it used a fair amount of oil and the oil was always black . It ran real good so I never bothered to fix it for 30 + years.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] What turns engine oil black? [message #245827 is a reply to message #245822] |
Sun, 30 March 2014 21:41 |
mikethebike
Messages: 331
Registered: January 2014
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If you want to see some rings that don't like to seat, try a BMW or Porsche engine with silicone/nickel liners and chrome moly rings. After 20,000 miles you get fed up with it and go out in 4 gear and run the thing as 7000 rpm for 2 tanks (12 gallons) and if that does not do it, go at 8000 for 2 tanks.
But I do have a question....are you saying 110 octane fuel has a combustion temp lower than 87 octane? Or did you mean to say it has a higher ignition temp?
| roy1 wrote on Sun, 30 March 2014 20:57 |
| BobDunahugh wrote on Sun, 30 March 2014 18:26 |
Why Rob. Black stuff does it. ( GRIN ) When I take any of my COPO Yenko Stingers road racing for a day or two. When I get home. The first thing I do is change my engine oil, and brake fluid. The brake fluid gets cooked due to the extreme temperatures. The engine temps generally stay under 200. I generally put about 300 miles on at around 6,000 to 7,500 RPM's So for the engine. The oil isn't that used. I'm just look shiney stuff in the oil,and filter material. One thing I have noticed is in the engines that have the gapless piston rings. The oil is always cleaner than the engine that has piston rings with end gap clearance. So to me. The darkening of the oil is mostly due to the blow by from combustion. I run 110 octane leaded fuel. I need as cold a burning fuel as I can get. As I have a compression ratio of about 13 to i. 87 octane fuel is too hot a fuel to run. So both types of rings are subjected to the same loads. When running a compression test. The gapless rings will
be at around 200lbs. The gaped rings will be at 160lbs. So guess what's getting to the oil. Black stuff.Bob Dunahugh
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Going by that theory I would suspect an engine with forged pistons would have darker oil then cast pistons because there is more piston clearance needed with forged pistons. The Molly rings never seated properly in my 455 olds boat engine so it used a fair amount of oil and the oil was always black . It ran real good so I never bothered to fix it for 30 + years.
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| Re: [GMCnet] What turns engine oil black? [message #245845 is a reply to message #245791] |
Mon, 31 March 2014 01:38 |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
Karma: 11
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Roy. Cast vs forged, and their clearance really won't have an effect on now the rings seal. And there is a thought that moly rings are hard to seat. Most of the time. It's how engine builder get off the hook for an engine that they built still using oil. The blame is easy to put on the moly ring set. I have never had a problem with moly rings seating. The lowest ring on a piston is the oil control ring. That oil ring has to control all the oil that is thrown off the crank at a very high feet per second. To top that off. The piston is also heading down toward the crank, also at many feet per second. This puts a big demand on that oil ring to handle the pressure of this oil directed at it. To really reduce the oil consumption of an engine that your building. That starts with the crankshaft. There are several things that I do to a race engine that can run to 8,000 RPM, or a GMC engine at 3,000 RPM,s. I make sure that the main, and rod bearings are at their absolute minimum fac
tory clearances. Anything over that is NOT acceptable. Check your lifter bore sizes. A bad lifter bore can dump a lot of extra oil in the crankcase. Check the cam bearing clearance. NEVER put in a high volume oil pump. Unless you have to feed turbo's. Or you engine is junk. And you want to get a few more years out of it. The minimum clearances will give that oil ring a chance to do it's job well. The engines that I build. Don't use oil because of these items. Next. The moly rings. That's what I use. I do like gap less for engines that I plan to not take apart for the long haul. The key to the uses of moly rings is in the cylinder wall prep. And a proper pattern angle on the walls. Next. NEVER neral valve guides. Replace the valves, and guides. Nothing less. As for break in. I pre fill the carb. Set the timing prior to start up. I have items so the engine starts just like I just shut it off 5 minutes before. After the start up. I have it run at 2,200 RPM's for one hour. I
f the engine was done correctly. That's all the so called brake in period needed. I've never lost an engine that I followed this process. That's my TWO cents.
Bob Dunahugh
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| Re: [GMCnet] What turns engine oil black? [message #245847 is a reply to message #245791] |
Mon, 31 March 2014 02:12 |
appie
Messages: 902
Registered: April 2013
Location: denmark
Karma: 2
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I have been wondering about this to Is there a difference between regular and syntetic oil?
The oil on my volvo hardly changes color between shifts at 20.000Km? it has done 180.000 Km
Appie
eleganza 76 "Olga" now sadly sold
6 wheel discbrake
Quadrabags
Springfield stage 2 462 olds
Manny tranny
( pictures at http://www.gmcmhphotos.com/photos/g6489-olga.html
Fulltiming in Europe july 2014 til july 2016
Denmark
[Updated on: Mon, 31 March 2014 02:12] Report message to a moderator |
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| Re: [GMCnet] What turns engine oil black? [message #245852 is a reply to message #245791] |
Mon, 31 March 2014 07:04 |
Ultravan Owners
Messages: 443
Registered: March 2013
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1) Long over due oil changes with cheap oil and filter.
2) Running rich and/or
3) Ring blowby
Tony (Ontario Canada)
Marie and I are blessed to have had a 2nd chance to buy our farm.
Still hoping and more importantly praying to be able to build a garage.
Our 1970 Ultravan #520 has an Olds Toronado 455 in back.
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| Re: [GMCnet] What turns engine oil black? [message #245864 is a reply to message #245845] |
Mon, 31 March 2014 09:51 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Bob -
What is the argument >against< higher volume oil pumps?
I don't know how relevant the two are, but we never had a problem seating moly rings in iron cylinders with flat motors. Fill them with mineral oil, put a test club on, and run them gently for about thirty minutes, then up the RPM to about 85 - 90 percent and run them till the oil temp showed a drastic drop in temp. Then, drain, check the filter canister for magnetic stuff, and fill them with Aeroshell AD and ship.
The oil temp drop should occur on an automotive engine as well, and is indicative of the rings seating and reducing the blowby (and therefore the oil temp).
I'll note, chrome plated cylinders took tens of hours to seat the rings, when and if they seated at all. Many didn't. Run an AD oil before they seated, and they pretty much never would seat.
==johnny
________________________________
From: Bob Dunahugh <yenko108@hotmail.com>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Sent: Monday, March 31, 2014 2:38 AM
Subject: Re: [GMCnet] What turns engine oil black?
Roy. Cast vs forged, and their clearance really won't have an effect on now the rings seal. And there is a thought that moly rings are hard to seat. Most of the time. It's how engine builder get off the hook for an engine that they built still using oil. The blame is easy to put on the moly ring set. I have never had a problem with moly rings seating. The lowest ring on a piston is the oil control ring. That oil ring has to control all the oil that is thrown off the crank at a very high feet per second. To top that off. The piston is also heading down toward the crank, also at many feet per second. This puts a big demand on that oil ring to handle the pressure of this oil directed at it. To really reduce the oil consumption of an engine that your building. That starts with the crankshaft. There are several things that I do to a race engine that can run to 8,000 RPM, or a GMC engine at 3,000 RPM,s. I make sure that the main, and rod bearings are at
their absolute minimum fac
tory clearances. Anything over that is NOT acceptable. Check your lifter bore sizes. A bad lifter bore can dump a lot of extra oil in the crankcase. Check the cam bearing clearance. NEVER put in a high volume oil pump. Unless you have to feed turbo's. Or you engine is junk. And you want to get a few more years out of it. The minimum clearances will give that oil ring a chance to do it's job well. The engines that I build. Don't use oil because of these items. Next. The moly rings. That's what I use. I do like gap less for engines that I plan to not take apart for the long haul. The key to the uses of moly rings is in the cylinder wall prep. And a proper pattern angle on the walls. Next. NEVER neral valve guides. Replace the valves, and guides. Nothing less. As for break in. I pre fill the carb. Set the timing prior to start up. I have items so the engine starts just like I just shut it off 5 minutes before. After the start up. I have it run at
2,200 RPM's for one hour. I
f the engine was done correctly. That's all the so called brake in period needed. I've never lost an engine that I followed this process. That's my TWO cents.
Bob Dunahugh
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] What turns engine oil black? [message #245872 is a reply to message #245870] |
Mon, 31 March 2014 11:31 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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OK, short answer: No benefit, some downside. Makes sense. Interestingly, I've had only one oiling problem with my coach, the cause being the one you doubt. The sender failed. Fortunately, it was fairly obvious what went, the gauge went to the high limit. Sixteen bux at O'Rielly's for another sender, ten minutes to put it on and test it.
--jonny
________________________________
From: Bob Dunahugh <yenko108@hotmail.com>
To: "gmclist@temp.gmcnet.org" <gmclist@temp.gmcnet.org>
Sent: Monday, March 31, 2014 12:24 PM
Subject: Re: [GMCnet] What turns engine oil black?
Johnny. The original pump was designed to supply the demands of the original engine. Then they added some extra capacity as a safety measure. I don't know what that extra percent was. The bearings, and lifters can only let a certain amount of oil thru. That's the demand. The extra is sent back to the oil pan by way of the by pass relief valve. Your oil pressure you see on the gauge, is the factory set maximum oil pressure the factory wanted. Thus controlled by the action of that relief valve setting. When you see a low oil pressure reading on your dash gauge. The cause can be. ! Bad gauge or sender. I would doubt that one. 2 low oil level. Thus air is getting in the pump. 3 Broken relief valve spring. 4 Oil pump is worn out. 5 Excess bearing clearance. 3, 4, and 5 are the biggies. 5 is where the high volume oil pump comes in. That can buy you some time. So just to put some numbers down. If the engine demand is 4 GPM's. The safety value is 1 GPM. So
that's a total of 5 GPM.
Most high volume pumps are 50% bigger. So why would you want to pump that extra 2.5 gallons of unneeded oil back to the oil pan in a good engine. The cost of that extra oil back to the pan is more heat buildup, and the HP to do the pumping. The question is. Why would you do that to a good engine? I know that there are guys that just think it's an extra benefit. Sounds good. Thus better. Why?Bob Dunahugh GMCMI Member
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] What turns engine oil black? [message #245874 is a reply to message #245845] |
Mon, 31 March 2014 11:37 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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I've built about a dozen automotive engines in my time (not counting air condition compressors) the 2 that had rings that didn't seat properly was a400 small block Chevy and a 455 olds boat motor they ran great otherwise and they both had double moly rings. That was about 35 years ago for both.at the time I suspected the machine shop didn't hone the cylinder properly for the Molly rings. The last motor I did was the GMC motor a couple of years ago I used single Molly rings on it and it is doing real good. Like you say the bore has to be right.
Roy Keen
Minden,NV
76 X Glenbrook
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