6-bolt 4g63 Crankshaft Chamfer & Oil Clearances

These are some things you need to think about during your build. Some engines don't have any chamfer on oiled journals whatsoever. All equipment like that can benefit from at least a light chamfer like the one that's on a stock Mitsubishi crank shown in this video.

When you Chamfer an oil passage, you create a low-pressure zone where the edges of the oil passage lift away from the bearing as it passes over it. The principles of fluid dynamics dictate that if there wasn't an available substance to displace that low pressure zone (in this scenario, there is an oil supply), cavitation might occur. If we were talking about aerodynamics, the effect would be lift.

An extremely-advanced or leading chamfer is actually capable of sucking oil off of a flat bearing, whereas a trailing chamfer vacuums oil out of a gallery and does a better job of spreading it around.

The modification that was performed here is intended to increase oil flow to the mains and the rods. It's mentioned in the video that I'm setting up my rod oil clearances on the looser side of spec. This will decrease block oil pressure because more oil will be able to leak past the fillets of the crankshaft and back to the pan.

But there's another modification being performed. A balance shaft elimination. There will be lots of debate about this in the coming videos as that transpires, but one of the side-affects of doing a BSE is increased oil pressure. With several internal oil holes plugged off inside the block, I will have a spike in oil pressure. I had my chamfers cut straight in order to offer the largest practical surface area to apply oil to the mains and rods. My intention is to relieve some of this oil flow that doesn't have anywhere else to go. With the added flow, the straight chamfer is actually beneficial to the mains, allowing them to intake more oil as well as to spread more of it on the flats below the grooved upper bearing.

The animations illustrate this completely. They were created by yours-truly. I know the oil hole on the mains is on the wrong side. It was too much work to fix, but they get the point across. Don't laugh at them any harder than I did.