Oil in 7 and 8

37fatfender

37fatfender

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I have about 500 miles on a fresh built 276 inch 8ba. A buddy said he noticed some smoke coming from my left exhuast tail pipe on a recent short trip. When I got home I pulled the plugs. The plugs in cylinders 1 to 6 looked good, the plug tips were light brown and pretty clean but on 7 and 8 the plugs were oiled and black. Any ideas whats going on? Should I adjust the valves, perhaps these two need adjusting?
 
Looking at the sparkplugs might or might not tell a story. Do a compression test and/or leakdown test before proceeding.
 
I'd check the valve guides/seals first, and if needed, pull those two pistons and check the rings.

Who did the rebuild?
 
really there are only 2 things that will will cause oil to enter the cylinder, worn or broken rings, bad intake guides, there are a couple of other factors, but those are the most likely
 
I knurl all my guides and set the valve stem to guide clearance at .0005.,001" and I install all my guides in the block with some RTV on the intakes and Never seize on the exhaust. Other builders may have differant methods to seal these areas, this is just one of them that has been working for over 20 years.
 
Since the compression is good, and reasonably equal, I suggest several full throttle blasts from 2000 to 4000 RPM in second gear to clean out the cylinders. There is no indication of broken rings. And, if tappets were loose enough to hamper performance it is likely they would be noisey.

To look at spark plugs after the engine has been idling or operated at low speeds with "coast-downs" is next to meaningless. At periods of very high vacuum, such as during an in-gear coast-down, when the throttle is closed but engine speed relatively high, residue can enter chambers from around the guides and stems and rings. That is normal and nothing to worry about unless excessive.
 
Could the rear baffle that covers the oil drainback holes in the valley be missing or displaced? --causing too much oil to be in that area of the valve chamber--

Is it possible that the ends of the oil ring expanders got overlapped on those 2 cyl?---compression would still be normal.
 
Thanks Everyone, for now I am going to drive it, After winter sets in I'll pull the intake and check the valve lash, and go from there. I am not in a hurry to tear down a fresh engine. How often should valves be adjusted? If the intake valve is opening late, too much lash ,might it be pulling oil past the rings?
 
Had an old Chevy truck once that had all the oil return holes under the oil rings plugged with sludge. I attributed this to a lot of hard work on the engine. Actually had to use a drill bit to clean them out. I doubt that is the problem here but someone did mention the oil rings.
 
Junkyard Dog said:
oil in cylinders in a fresh rebuild wouldn't bother me drive the piss out of it
then see w hat it looks like
Click to expand...

Had a guy babying his AH 3000 after a fresh rebuild and eveb with good leakdown numbers it used a lot of oil. A good hard run on the pike cured that one.
 
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