Well, we decided it was time to crack the seal and see what is living in the dark places under the spark plugs. As you can see from the picture, I would say bleu cheese. We will be pulling the motor this week and dig further. So far (other than the carbon build up) things do not look "too bad". Some scoring on 2 cylinder walls but I will not know the extent until the pistons are removed. She has been running well with the exception of having a thirst for oil. You could be sure if you were behind me on a drive, you would Not have to worry about mosquitos!
Patrick -- It looks as if your engine still has its original two-piece valves. I'd recommend that you replace those, since they have been known to come apart and make quite a mess.
Mike, I had not thought of that though I remember reading about it somewhere. Thanks! Valves and rings were definitely on the list to check... I will verify the valves.
Take your hand and push back and forth the pistons. Do they rock back and forth in the cylinders? If so, rings might not fix your problem. You also need to mike the cylinders for roundness and difference in size from bottom to top of the cylinders. It is very likely the block should be re-bored and pistons replaced.
I had a car which I restored about 12 years ago, but only put in rings and ground the valves. Also poured new bearings. That car always had a knock which I could not fix, and it had very poor hill climbing ability. When I restored the car, I only did minimum work on the engine. It resulted in only using the car in car shows and parades, because it didn't tour very well and our parades go downhill at a speed I can almost coast in neutral.
This last summer I decided to pull the engine and rebuild it. It was 60 thou over and the pistons had 15 thousandths clearance at the skirt to block. I installed new camshaft, new crankshaft, bored and resleeved the block to standard size new pistons and rings and all new bearings, new timing gears including the generator gear.
This rebuild cost a lot even though I did the disassembly and reassembly work myself. It is now very smooth running and has more power than ever before. It is quiet and idles better than before.
Anyway, before you put in rings, you need to go through the entire engine and fix EVERYTHING you find wrong. In the long run it will save you a lot of wasted time and money.
Norm, I have to agree. Because it was running as well as it was before surgery, I was hoping to find that I only needed due diligence, however I intend to identify and fix everything (within budget) this go around. I appreciate your candor!
Here are some of the problems with pistons which are too loose. They knock (piston slap). If the cylinders are out of round, the rings either don't seat, or take a long time seating. When the pistons rock back and forth and the rings go in and out due to tapered cylinders, the edges of the rings wear out rapidly and the grooves in the pistons also wear out, causing it to pump in oil and blow out compression. You might also have noticed blowby in the crankcase. The wet carbon deposit also indicates oil burning.
Per your suggestion, I tried rocking the pistons back and forth and all of them will move 1/32 to 1/16 of an inch and the rings are quite visible from a top view. Not sure if this is correct or normal as I am an IT guy by trade. I do my best with autos and rely on my friends and this forum for advice, and will gladly repay the favor should a computer question arise. I am not familiar with the 2 piece valves as Mike Walker pointed out, but it looks like the motor is in original condition so I am going to replace those as well. The bands were replaced with Kevlar in the late 90's/early 2000's by the previous owner so hopefully I am good there. Again, my thanks for your thoughtful advice!
Patrick -- I sent you a message through the Forum system. If you don't see it in your inbox, check your junk mail folder.
The clearance for new aluminum pistons is .004-.005. 1/32"-31thousandths. Mine knocked with 15 thousandths. Yours is twice that.
It's time to bite the bullet and rebore with new pistons.