[Walt Fricke]

I will have to beg to differ with our esteemed moderator on this.

I believe the tolerances around the oil pump gears, both between gears, between teeth and the housing, between the ends of the housings and the end faces of the gears, and between the gear shafts and their bearing holes through the housing ends and separators, are sufficient for oil to leak through. At what rate I don't know.

It can exit on the flywheel side through the shaft openings there, and from the other side after passing through the intermediate plate or whatnot on into the pickup tube.

After passing through the mesh and around the gears, I once thought perhaps it could clamber up into bearings, but it has to go up too high to do that.

It could leak past either of the oil pressure pistons. The vertical one would just leak it back into the inlet, so that wouldn't count if it could get up that high. But the safety relief just dumps right back into the sump.

But from my experiences with trying to stop oil from leaking elsewhere, I am convinced that it is slippery stuff, and zero is the only tolerance which will stop it. None of these parts need to be leakproof.

A guy with a pump apart could measure its tolerances, especially from gear to case at the teeth, easily with feeler gauges. Since most of us are baffled on how to tell if a used pump is good, maybe someone or some discussion has this information already? Then one might be able to calculate/approximate the flow rate of 50 weight oil at room temperature through openings of such a size.

Were I possessed of even more free time and curiosity than I already have (on showing someone my latest fitting with small lightening holes, my friends exclaimed: "Walt, you have to get a job!"), I could figure out a way to do an experiment. I have the oil pump from a 1968 or so engine. Not likely to be useful to much of anyone. I could make a jig - maybe from the mag case with pulled timecerts I keep for who knows what use - to hold the seals, and rig a gallon jug a foot or so above the pump, fill with oil, and watch what happens.

What I do know experientially is that the level in the oil tank drops after the engine is shut off. Where does that oil go? Since it enters the tank from the oil filter up top on the tank, it can hardly go back that way. That leaves only the S tube directly into the pump.

I've never measured this, but I don't believe that the dribble down of oil from the various surfaces inside the case and up in the heads can amount to more than a pint, if that. Not all that much oil is sequestered in the heads below the level of the return tubes.

Though I admit that when I need to get into the exhaust valves outside of an oil change, I jack the car way up on one side, and then on the other, to avoid the mess. So maybe a) the oil level is higher quicker than one might think in the sump, or b) oil drains from those areas slower than I am asserting it does.

Myself, I think what is important about valve guides is to replace worn ones (and worn valve stems, too) before more problems than just a few ephemeral puffs of smoke show up.

To get back on Bob's topic, I think he needs to measure oil consumption. If it is low, I think that is some indication that his guides may still be in OK shape. And if it is down in the 500 mile per quart range, maybe he needs some serious examination of his guides.

That's my case, and I'm sticking with it.