I've been reading Tom Monroe's bookEngine Builder's Handbook and come across an oil problem I can't quite figure out. Here's the text from book: "Although the rings may not be faulty, excess oil can get past the pistons and into the combustion chamber when more oil than intended is thrown onto the cylinder walls. This is caused by excessive bearing-to-journal clearances at the connecting rods. The looser bearing clearances allow more oil to pass between the bearings and journals." I just don't get it. How is the oil splashing around below the piston crown going to get into the combustion chamber, above the crown? Aren't the oil rings there to pick up excess oil? When compression takes place, the piston rises, so how is it excess oil gets burnt because of loose bearings at the connecting rods?

By saying “excessive bearing-to-journal clearances at the connecting rods” he’s telling you there will be slop at the rings as they won’t stay seated properly causing oil to be sucked past them during the intake stroke.

what is this "slop" you speak of? I understand the oil passing through the excess clearance, but what slop causes the rings to loose effectiveness?

I think what he is saying is that the slop or excessive play causes blow by because the piston is not square in the bore. And because it is not the rings arn't as effective. Not to mention the increased wear on both the piston and the bore causing more oil consumption. The same thing happens if a rod is bent or twisted.

Is this a fresh build, or an 'old' engine? Are you just inquiring about what you read?

Kids not a mechanic, just a wannabe. Doesn’t know the difference from a V-8 to straight six or what a blower is for. Wants to buy a cherrypicker for whatever reason I don’t know. Doubt he’d ever figure out how to unbolt an engine and pull it out of any vehicle successfully let alone tear one down to rebuild. He’d be lost.

You're quick to judge. You assume many negative qualities about me and insult me. Yes, I am wannabe, but noone enters this world with knowledge. Knowledge is earned. I chose to gain it from those more experienced than I. Very intelligent people reside here with great insight to share. What more then selfishness would intelligence and wisdom offer if the proud withheld for themselves? I am asking those kind enough to help me and you meet me with harsh words and assume I can't tell the difference between 6 and 8. You antagonize me for asking a question that may seem simple to you, but perhaps not everyone has had the opportunity to work with cars and knowledgeable people such as yourself. There are many people who do not seem as intelligent as yourself, but don't be quick to degrade them. You don't know their lives or their cause for senselessness.

Cause for senselessness? I think you described yourself perfectly.

I'm confused. What does this post have to do with the thread subject?

It has everything to do with the question. Kids been asking questions and BSing posters of his aspirations. Reads a well-written book on engine rebuilding and posts a question. Gets a response and it becomes evident he wants to play Socrates with words.

Take a pill dude.

Nothing in this statement of yours is correct. Ring effectiveness and piston to bore clearance have nothing to do with bearing clearances, but excessive bearing clearances can throw more oil on the cylinder walls than the oil rail rings have the ability to control. Think of windshield wipers in a very heavy downpour.

Is "slop" a technical term??

It has nothing to do with ring seal. Rings don't seal, they mostly seal. In a properly running engine with good rings, a tiny bit of oil still makes it past the rings. It has to, otherwise there is no oil left on the cylinder walls to help lube the piston. They are designed to wipe most of the oil and hold in most of the combustion gasses, so if you put more oil on the cylinder walls below the piston, there will be more left over to sneak past the rings.

Sometime park your engine sideways on a steep hill. The downhill bank will start burning massive quantities of oil simply because the oil has flowed over to that row of cylinders. The same is true (to the extent that I agree with Monroe... which I don't really.) with loose rod bearing tolerances. If they're slinging more oil on the cylinder walls, more will get past the rings.

here is what the writer is trying to say: The amount of clearance between the rod bearings antd the crank is a critiacal space. It will fill with oil when the engine runs. If there is too much clearance the oil will sling out (also causes oil pressure to drop). The excess oil will sling every where in the crankcase. The general rule of thumb is for every .001" of excessive clearance you will get 4 times the amount of oil on the bottom of the cylinder. So if you had .002" above spec. clearance you would have 8 times more oil on the bottom of the cyl wall. The oil rings can not scrape that much oil off. Remember they do not ride on the cyl wall, they ride on what is suppose to be a thin film of oil. They will begin to "hydroplane" on the oil and lose control if there is too much. The top two rings are compression rings and offer very little oil control. Their job is to keep compression in the cyl and help make power. They twist under the up and down force of the piston and offer resistance on the down strokes and than much less on the up strokes. .....engine bearings can cause excessive oil consumption....give people who don't know as much a chance to learn with out ranting on them. We all started out not knowing much about this great hobby/ sport.

I you have too much clearance between the rod bearing and the crank you are going to have a rod knock. That in turn is going to jerk the piston on each stroke. Oil will slip past the rings, as they aren’t designed to handle that sudden motion. It needs to be a smooth transition for the rings to stay seated properly. Eventually, damage will occur on the cylinder walls and rings.