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.