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Black oil

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bud45

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Hopefully, this is the right forum/area for this question: I have a '65 283 in my '69 GMC. I use a high quality oil filter (synthetic media) and Castrol 5W30 oil, with one quart of Lucas Oil Treatment. After about 500 miles after the oil changes, the oil is black. Now, this engine doesn't have a PCV valve, just a breather on the oil fill tube and at the rear, behind the intake manifold, an elbow with a "slobber tube" attached going down below the oil pan. I added the tube because oil residue was dirtying the engine at the rear, making me think I had a rear oil seal leak at first. Would it NOT having a PCV valve system cause the oil to be black, or do I need to put a better, tighter breather at the oil fill tube?

I usually change oil between 2500 & 3K miles, but this has me a little concerned. I thought of doing an oil analasis & seeing if the oil is doing it's job (capturing dirt) or if it's gas byproducts... but this engine has been recently rebuilt, possibly within the last 5-6K miles and then was driven little before being transplanted into my truck.

Another thought: I have a carb from a '66 283 that has a PVC valve at the lower rear of the carb body, which would just take a short piece of my "slobber tube" to connect it to the elbow at the rear of the engine. Could rebuilding this carb (just for newness-sake) and installing it help the oil situation? Or could it contribute to gas byproducts being intro'ed into the lube system?

Thanks for the help
 
Interesting situation you have there. Oil is usually black because it is full of dirt. I know from experience that Castrol oil cleans very well. Maybe you should consider taking off a valve cover or the oil pan and having a look for your self. Good luck.
 
The engine is clean, Velcro...I had the valve covers off before the last oil change, adjusting the valves & it's not gummed up or fouled at all...in fact, it was amazingly clean. The fellow who dropped it in for me had the oil pan off, replacing the main bearings, since the crank had been turned .010 and the rebuilder put in standard bearings in error. It holds about 45psi oil pressure, too.

It had a small, cheap crome-crap Mr. Gasket air cleaner on it also, but I since located a full-size OEM '66 air cleaner for it & installed the proper air filter, which is HUGE! I was concerned that the cheapo air cleaner was letting too much crud through. I've changed the oil since I got the proper air filter on it. I do live on a dirt road, but it's only 1 mile or so to pavement and I don't roar along it raising dust. Most of my driving is city, about 25 to 40 MPH, with about 6 out of 26 miles round-trip being interstate. I just wonder if the slow speeds could have something to do with it?
 
>The engine is clean, Velcro...I had the valve covers off
>before the last oil change, adjusting the valves & it's not
>gummed up or fouled at all...in fact, it was amazingly
>clean. The fellow who dropped it in for me had the oil pan
>off, replacing the main bearings, since the crank had been
>turned .010 and the rebuilder put in standard bearings in
>error. It holds about 45psi oil pressure, too.
>
>It had a small, cheap crome-crap Mr. Gasket air cleaner on
>it also, but I since located a full-size OEM '66 air cleaner
>for it & installed the proper air filter, which is HUGE! I
>was concerned that the cheapo air cleaner was letting too
>much crud through. I've changed the oil since I got the
>proper air filter on it. I do live on a dirt road, but it's
>only 1 mile or so to pavement and I don't roar along it
>raising dust. Most of my driving is city, about 25 to 40
>MPH, with about 6 out of 26 miles round-trip being
>interstate. I just wonder if the slow speeds could have
>something to do with it?


HELLO,

OIL LUBRICATES THE TOP OF THE CYLINDERS AS WELL AS THE INTERNAL MOVING PARTS, BUT ONLY IN THE COMBUSTION CHAMBER AND TOP OF THE CYLINDERWALLS DOES IT EXPERIENCE TREMENDOUS HEAT.
ALL THE CONTAMINANTS OF THE AIR/FUEL CHARGE FROM DIRTY AIR OR WHATEVER BURNED INTO THE FILM OF OIL AT THE TOP AND CYLINDER WALLS. THE NEW OIL BEING PUMPED THERE ACTS AS A SOLVENT AND PULLS THE CONTAMINANTS INTO THE CLEAN OIL CONTAMINATING IT.
HENCE THE REASON FOR CHANGING THE OIL.
PUTTING A PCV IN WILL CONTRIBUTE TO THE "PROBLEM".
THE THIN WEIGHT CASTROL YOU ARE USING IS THE REASON FOR THE DISCOLORATION IN THE OIL.
JUST BECAUSE IT IS BLACK HOWEVER DOES NOT MEAN IT HAS LOST IT'S VISCOSITY AND THE ABILITY TO LUBRICATE.
CERTAIN BRANDS, WEIGHTS AND GRADES OF OIL WITHSTAND HEAT BETTER THAN OTHERS.
I WOULDN'T BE LOOKING FOR A SPECIFIC MECHANICAL PROBLEM AS MUCH AS I WOULD LOOK AT TRYING DIFFERENT OIL.
STAY AWAY FROM OIL THAT IS NOT PETROLIUM BASED, SOME ARE WAX BASED AND HAVE A TENDENCY TO SLUDGE UP.

HOPE THIS HELPS.

BRANT
 
Ok, Bryant...and I stay away from Penzoil and Quaker State for the "sludge" reason. I've used Kendall in the past, but can't seem to find it here; I also used Havoline, both in 10W40 grade, but have since started using 5W30 Castrol, since I use it in my wife's Jimmy (which, incidentally, stays pretty clean up to 4K to 5K miles). I used to use 10W40 Castrol in the truck when it had a 250 inline six, but am using the 5W30 for convenience.

Maybe I should change the oil & have an analasis done to see if anything is breaking down or if it's just getting really dirty for some reason (contaminants). The engine's running a bit rich, so I wonder if it's gas wash-down? I've also considered putting a K & N filter cap on where the standard breather/oil fill cap is, since I can see evidence of "breathing" there (some very small oil residue on the fill tube below the cap).

I'm running R45 & may go to R46 to see if THAT cures the rich-running problem; if not, then I'll rebuild the carb- the air screws are all the way out now & it doesn't make a difference.
 
HELLO,

WELL AN OIL ANALYSIS WILL DEFINITLY TELL YOU WHAT THE SCOOP IS, BUT I THINK YOU HIT THE NAIL ON THE HEAD WITH THE "TOO RICH" THEORY. GAS IS A SOLVENT AND WILL "WASH" THE CYLINDERS. IN TURN WILL CONTAMINATE THE OIL MUCH FASTER. HOWEVER THE AMOUNT OF GAS WOULD HAVE TO BE CONSIDERABLE, SUCH AS STUCK FLOAT OR IN THE CASE OF A HOLLEY, A BLOWN POWER VALVE.
YOU MENTION THE MIXTURE SCREWS ARE ALL THE WAY OUT. IN MOST CASES THAT RICHENS UP THE AIR/FUEL AT IDLE ONLY.
MY QUESTION IS, WHAT HAPPENS IF YOU SCREW THEM IN ALL THE WAY?
ANY CHANGE NOW?
USUALLY I START WITH 1-11/2 TURNS OUT FROM SEATED IN POSITION

HOPE THIS HELPS OUT SOME

BRANT
 
Well, Bryant, from what was taught, that the more the screws are out, the leaner the mix, but I screwed them in anyway and the air (and the grass under the tailpipe!) turned black with unburned gas. I screwed them back out again & got back to a rich, pungent gray gas smoke. I wonder if something internal is wrong...I have a carb off a '66 283 that I'll have to block off the PVC valve & try.
 
Wow , if you screwed the mixture screws in all the way or out all the way and the motor didnt die, You have a major carb problem. The motor should die before the screw is bottomed out. You should also pull the plugs and read them. They should be chocolate brown in the perfect situation. How high is the idle screw set? Sure sounds like your dumping gas in there...
 
Well, smoov330, it never seemed to falter...the smoke just got richer & blacker as I screwed the screws in and the engine kept it's "rumpety-rump" right along. I feel like it'll take a carb rebuild at the least....

I haven't pulled the plugs in several weeks, but when I got the engine, the seller installed R43 plugs, which fouled after a week. after three cleanings, I went & talked to a favored engine guy at the local auto parts (who's since moved away) & said that engine ought to have R45 plugs. Since I changed them, no more fouling, but still a rich condition. I think I see what direction I need to go now. Thanks.
 
HELLO,

YEP SOUNDS LIKE CARB TROUBLE, PLEASE LET US KNOW ABOUT THE USE OF THE OTHER CARB.

GOOD THINGS.

BRANT
 
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