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07-13-2015, 08:45 AM
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#1 |
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Registered User
Join Date: May 2011
Location: Fort Pierce, FL
Posts: 430
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Dirty Oil on a 72 350
My 72 Cheyenne oil turn BLACK after just a few miles. I have owned since 2003 and changed oil regularly, so it's not change a few times and it'll clear up. Truck runs fine...just drive 2000 miles on vacation, but oil very black after a couple hundred miles. As far as I know, the mileage is 107K. My 72 Olds 350 with 225K stays clean for 3000 miles. Engine doesn't smoke.
Any ideas? |
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07-13-2015, 09:39 AM
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#2 |
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Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,533
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Re: Dirty Oil on a 72 350
Gas from light flooding will get past the rings and make your oil turn black. Or a fuel pump that's starting to die will leak from the diaphram into the motor.
What carb, what fuel pump you got? |
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07-13-2015, 12:08 PM
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#3 |
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Registered User
Join Date: Jul 2010
Location: MD
Posts: 1,937
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Re: Dirty Oil on a 72 350
A poorly working PCV system can cause carbon buildup in the crankcase as well.
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07-13-2015, 02:13 PM
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#4 |
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Registered User
 
Join Date: Jun 2015
Location: Ephrata, WA
Posts: 308
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Re: Dirty Oil on a 72 350
You have to change the oil filter when you change the oil.
 But seriously... could be PCV valve, I had a Ford (go figure) that had the same problem, ended up pulling the oil pan, was full of sludge even though I changed the oil regularly. Could have been there from a long time ago. Cleaned it out and put it back on. Oil stayed much cleaner for much longer. Just a thought.
__________________
68 C10 SSB 383 12 Charger 6.4L 12 Accord 3.5L (Wife's ride) 05 Ram 1500 5.7L My build thread - http://67-72chevytrucks.com/vboard/s...d.php?t=676545 |
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07-13-2015, 04:18 PM
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#5 |
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Registered User
Join Date: May 2011
Location: Fort Pierce, FL
Posts: 430
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Re: Dirty Oil on a 72 350
Everything is stock...correct Q-jet, air cleaner and mechanical fuel pump. It has been doing this for years and other than black oil, starts, idles, runs perfectly. I haven't checked the PVC in a while, so that is worth a check.
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07-14-2015, 08:00 PM
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#6 |
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Registered User
Join Date: Jan 2012
Location: Washington,Il
Posts: 632
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Re: Dirty Oil on a 72 350
Correct me if I'm wrong ,but the "black" you are referring to is from carbon/soot from combustion by products. Could be blo by the rings? broken ring,loose valve stems. Compression/blo by test in the future???
__________________
It builds on my intelligence when I make a mistake, Boy am I building on it! '67 C-10,'70 Nova SS 
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07-14-2015, 08:03 PM
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#7 |
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Registered User
Join Date: Jun 2013
Location: Somewhere
Posts: 3,066
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Re: Dirty Oil on a 72 350
I'd pull a valve cover and look for buildup.
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07-14-2015, 08:08 PM
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#8 | ||||
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"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,921
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Re: Dirty Oil on a 72 350
Old Q-jets are notorious for leaking fuel from the well plugs after engine shut down and letting raw fuel seep past the rings into the crankcase.
Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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07-15-2015, 02:05 AM
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#9 |
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Registered User
Join Date: Dec 2009
Location: bisbee, arizona
Posts: 1,529
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Re: Dirty Oil on a 72 350
with 107k on it thats kinda typical for the older trucks. check your pcv valve. pull a valve cover to evaluate sludge build up. high detergent oils will be flushing sludge out for ever.
I seem to recall that the oil got black....not nessessarrily dirty after only a few hundred miles in older vehicles. since its not using oil thats nothing to be too concerned with now when you use 3 quarts in 105 miles and your oil turns black.....yea... thats cause for concern. |
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