Bolllocks.
Like a chump, I had left the main and cam bearings in the saddles (held in place by their alignment dowels) until I was ready to do the thrust measurements for each bearing saddle. "Thrust" measures the front to rear slop of each bearing inline with the crankshaft. Add up all of the 'thrust' slop and you have a total potential for what is called 'End Play' which isn't as kinky as it sounds. It means 'how much total total distance the crankshaft and flywheel can float forward and backward in the case. There are shims which you can add at the flywheel end that can reduce end play to a carefully calibrated range between .003" and .005" so the flywheel doesn't drift too much, but isn't so tight that it grabs the #1 bearing (zero distance) and eats it at 4000 RPM. (Bearings are not supposed to spin!). I carefully removed each of the bearings and alignment dowels and stored the set away and then took a good look. Great googly-moogly.
I saw that the bearing saddle for the #2 crank journal was looking...odd. But I decided for my own sanity that I was going to start at #1 (the flywheel end) and work my way back to #4 at the impeller (fan) end.
One oddity about how I work on my cars now is that I wear gloves. Always. I always wear nitrile exam gloves that are a skin tight. This isn't because I'm some priss afraid to get his hands dirty. (Though I don't like it and it is a nuisance.) It is because I earn the bread that my family eats with my hands. They type very, very fast in a high pressure job, where my keyboard has all of the lettering worn off and the keycaps polished to a gloss like Dath Vader's helmet. I cannot afford damage to my hands, as the computer environment I work in doesn't use a mouse. Two years ago I busted my collar bone and was out of work for 5 weeks. I almost lost the job. To injure my hands in some of these antics is courting disaster, so I protect them all the time.
Wearing those nitrile gloves has other benefits though: they not only keep the grease out from under my fingernails, when my hands have become completely caked with grease from wrestling something into or out of position, I can take a break and put on a fresh set of gloves. Clean hands in 15 seconds. And rather than the slip of a screwdriver slicing open my hand, it just slices open the glove and my hand gets away with a mild to moderate scratch. Very handy, those gloves.
I saw the edge of the bearing saddle on the #2 and ran my hand across it...and my glove split open across my palm! I got strong light into the area, looked closely and felt sick.
See what appears to be a chamfer across the bottom edge there? That's not a chamfer or bevel. It is a lip of metal sticking out and overhanging the vertical portion of the bearing saddle. And the horizontal edge sliced open the glove on my palm like a cut-throat straight razor. Carefully dragging a fingernail up from the bottom to the face of the saddle will cause it to STOP against the huge lip pounded onto the edge of that saddle.
The steel bearing that fits in this saddle has been pounded so hard and so long that it has deformed the underlying metal of the saddle, despite the reputation of these cases for being 'virtually bullet proof.' Certainly I can have it align bored, removing perhaps .5mm of metal from the surface of the saddles. But then I'll need to drive the case at least 2 hours and pay $120-150 for the work. The OEM Kolbenschmidt bearings won't fit, either. They're 'Standard/Standard' aka not machined larger on the saddle side to take up the space removed, nor made larger on the inside diameter to make up for a crankshaft that has had to be trimmed 1/100th of an inch to remove grooves or burrs. These bearings go to waste if I don't have a perfect crank, and a perfect case to put them in.
What's a girl to do?
No comments:
Post a Comment