Join Date: Jul 2006
Location: Northfield, Illinois
Here is a quick, simplified answer.Most crankshafts are "cross-drilled" to carry pressurized oil to the bearings. The only way to create a gallery through the crankshaft is by drilling it. The "holes" were access holes for the drilling, as the gallery interconnects within the crankshaft. The drill access "holes" were factory plugged with aluminum plugs. With Alfa's, it has been found that sometimes, not often, these aluminum plugs will come out and allow the pressurizes oil to escape from an unintended area. On Alfa engine rebuilding, it becomes an optional procedure to drill out the aluminum plugs, and tap the drill access hole for a screw-in type plug as shown above. The plugs are usually sealed with Loctite Red, preventing them from unscrewing. To remove them for gallery cleaning, heat needs to be applied, directly to the cap plug, with a torch. They then can be removed. Threading for these in a hardened crankshaft, can be difficult, and break taps. The easiest way is to grind through the hardening with a die grinder before attempting to tap. The hardening is usually about .020" thick. Even then, this requires some patience, as the crankshaft is still a hard forging. The reason this is not done by factories is a matter of time and labor. Also, for most applications, the OEM aluminum plugs are adequate.
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Illinois SNO Alfa Chapter Director
Illinois SNO Ferrari Chapter Director
and sometimes, CONFUSED AND INCORRECT, but Larry helps me out.
Illinois Chapter Director AND Charter Member of THE CONFUSED AND INCORRECT