Combustion products in oil

philminotti · #1 (**permalink**) 10-20-2010, 05:31 PM

I've had my 482 running on a test stand for a total of about 6-8 hours. The first time I changed the oil, it reaked of gasoline. The oil at the bottom of the pan was black. After that first oil change, I pulled the heads for another reason, and there was no sign of a head gasket or intake gasket problem. Another oil change after another few hours of running showed the same problem.

My fuel injection system has been extremely rich. Perhaps an overly rich condition washed down the cylinders and prevented proper ring seating? I can't think of another explanation.

I'm going to tear down the motor, check the bearings and re-ring it...possibly hone the cylinders if necessary.

Can anyone think of other reasons why oil would be grossly contaminated with combusion products/gas? Like I said, when I pulled the intake and heads, there didn't appear to be any leaks.

Thanks for any ideas.
phil

blykins · #2 (**permalink**) 10-20-2010, 06:00 PM

Just running rich will do it. If your system was really fat, then it could cause those problems.

Also, you can't really expect to break-in an engine on a test stand. You need to have it on a dyno or in a car where you can put a load on it. Otherwise, it will take forever for the rings to seat, if at all.

undy · #3 (**permalink**) 10-21-2010, 03:17 AM

Re-honing the cylinders would be a must...

RICK LAKE · #4 (**permalink**) 10-21-2010, 03:27 AM

PhilM Phil you got a new motor with no miles and 8 hours is nothing with no load being applied to the motor. Running a little rich with a new motor is fine for breakin and first 20 hours. On a stand about 12.5 A/F I do with mine at 2,000 rpms, after that setup for the street with 12.7-13.1 ratio and idle in the 13.9 to 14.2. Still soft but no possible way to lean out and burn any thing.
Don't pull the motor apart, do a leakdown check first. The oil is going to look real bad for the first couple of oil changes. Do a 3rd change with the oil you are going to run for an hour and just cut open the filter and look for any metal in the pleats. The oil is cooked from breakin, the additives for the bearings, it is mostly zinc and it is black like coal when cooked.
You have good oil pressure? The motor has a steady coolant temp once warmed up? No strange noises coming from it when running?? Run it some more, change the oil and leave the beast alone until you do a 3rd change. IMO the motor needs a load to help with breakin. Engine stands work good for fireup of the first couple of times. Light loads are what is needed and varying rpms like first couple of road tests and normal rpms. When with the correct cross hatch and detph for the rings to breakin at you are still looking about 500 to 1K miles before final total compression numbers are known. Leak down test and check the filter. Rick L. You see bronze or copper looking material, pull pan and start to recheck. Cam shaft bearings need to breakin and I have seen shavings come from them and found no problems with bottom end. The motor should still have breakin material inside the bottom of the oil pan and lifter valley. This is why your oil is still nasty. Mine was the same way for 6 oil changes and then started to clear up. Just keep checking the oil filter. Only pulling the oil pan will give you a 100% actuate knowing of the motor. There should be some crap in the bottom of the pan. Rick L.

Barry_R · #5 (**permalink**) 10-21-2010, 04:21 AM

You answered your own question. Really rich running will fill the oil with fuel. Fuel is a poor lubricant, but you're also not putting any load on the engine. Load and the resultant cylinder pressure is what seats the rings. Eight hours is a very long time to run an engine with no load. On our dyno work we'll rarely give the engine more than 30 minutes before WOT pulls, and even during cam break in I will cycle moderate load into the engine - something you cannot do in the car or on a stand.

philminotti · #6 (**permalink**) 10-21-2010, 05:30 AM

Thanks for the replies. When I really thought about my run time, I realized that 6-8 hours is a huge exageration. It's probably closer to 1.5 hours. Interestingly, I've gone through at least 6 gallons of gas in that amount of time, again no load.

As I stated in a previous thread, i'm ready to pitch my injection system in the garbage. I've spent the better part of 18 months trying to get it right.

Maybe the cobra gods are trying to tell me something..

MOTORHEAD · #7 (**permalink**) 10-21-2010, 05:38 AM

Phil:
what injection system are you running??

philminotti · #8 (**permalink**) 10-21-2010, 05:54 AM

I have a Mass-Flo system. I'm in no way disparaging the system, and there are several members here who have well functioning systems, but I just have not had a fun time with it. Very discouraging, especially since as a former electrical engineer, I consider myself a pretty good diagnostician. Oh well.

blykins · #9 (**permalink**) 10-21-2010, 06:12 AM

What is the A/F ratio?

You have a mechanical failure somewhere that's just dumping raw gas into a cylinder.

MOTORHEAD · #10 (**permalink**) 10-21-2010, 06:33 AM

We had a new high dollar engine ruined because of too rich FI washing cyl walls. It happened quickly, before we found someone who could set it up properly. Walls were scored, burning oil. Had to send engine back for o'haul, and this time they got the right program in the computer, and all is well. EFI is not forgiving of learn as you go programing.
Get someone who knows the system to help you. Maybe send it back to factory for bench test.



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