Contaminated Oil

[BK]

How long does it take to contaminate oil from a rich condition? Im running a tunnel ram with dual 600 Holleys on my BBC, it runs on the rich side (im still messing with idle mixture and jetting) and after just one day on the lake I notice my oil starting to darken. Could it get like this from just running rich at idle or would it have to be from an all around rich condition? I have 4 seasons on these heads so mabye its leaky seals? Its a 10 quart pan with Valvoline VR1 20/50 racing oil.

[Moneypitt]

In extreme cases, not long. However, the color of your oil COULD be from excessive bearing temperature. Smell it, does it have a burnt smell, or does it smell like gas. A mild "rich" condition, assuming your rings are intact, would take alot of cold,(leaving unburned fuel) running time. BUT if you're having a flooding,(high or stuck floats) problem, the oil can, and will, thin out quickly which adds to the bearing temperature factor, and colors the oil dark sooner than expected. Another thing to check, after you turn the motor off, pull the air cleaners and check for fuel percolation, dripping out thru the venturi while sitting. This results in hard starting,(way rich) and black smoke after starting, with raw fuel getting past the rings into the pan.. Once again, smell it...Just my .02.......Moneypitt

[Dennis Moore]

I don't think oil will change color from gas dilution. Oil will change color from exhaust gases leaking past the rings and into the crankcase. With only breathers on the valve covers (no PCV) the oil will get dirty very quickly. All engines need some way to pull the exhaust gases from the crankcase other than just breathers. PCV valves work very well to keep your oil clean and only function at engine idle, they don't effect high speed performance.
Sincerely
Dennis Moore

[BK]

I dont like the sound of the excessive bearing temp thing! I have good oil pressure all the time, 35-55 pounds hot (been that way since motor was new 4 seasons ago) with a standard Mellings pump and tight clearances. What would cause the excessive bearing temps? The motor runs great, no problems with starting, idleing, black smoke ect.... the plugs just look real rich at idle but ok otherwise. Althoug they did load up on me real bad a couple weeks ago from too much
starting/stopping around the cliffs and I had to change them. I'll ckeck the smell of the oil tonight.
Dennis, im running a pcv on the back on one valve cover and breather on the front of the other. I notice very little oil on the foam in the breather and none on my valve covers.
Im real concerned about Moneypitts suggestion as im leaving for a 4 day trip to the Delta Thursday and dont want to hurt my motor!
[ August 18, 2003, 11:17 AM: Message edited by: BK ]

[RandyH]

BK, For what its worth my new motor was jetted way too rich last year and after two runs my 10 qaurts of Kendall 20-50 was pretty black. All I have is a breather in each valve cover . I was too busy chasing other demons last year to rejet.
I had other problems but long story short, with a new motor this year jetted correctly my oil is looking almost new and I was even having some idles issues and the floats where too high on my new Bigs. Just got that fixed this weekend and still the oil looks great.
My old pistons where black on top. I was running way too fat last year and the number 4 main didn't look that good.
Good Luck
RandyH

[BK]

Yeah thanks Randy that does make me feel a little better. I just went down a few jet sizes for this weekend and i'll see how that does, plus messing with idle mixture a bit. I was using the Kendall 20/50 till this season, thinking about going back to it. Wouldnt excess bearing temp mostly be caused by clearances? The thing about it that doesnt add up is ive been running this motor for 4 seasons, wouldnt something have happened by now? I would think it would have caused a problem allready if that was an issue? Thanks for the input.

[Moneypitt]

That bearing temp comment was only one of several possibilities for dark oil. The info about exh gases was right on, as well as the advantages of the PCV system. After 4 seasons, what changed? Carburation...I can't argue with success, but the 20/50 may be a little thin for a hot boat. Straight 50 racing is MY 1st choice, but that's only my .02........Moneypitt

[BK]

Actually its allways had this problem, just seems to be worse now. Im gonna take some of the oil from the oil change I just did to get anilized(sp?) here in town, that should tell me whats going on in there?