I must say that I raced A 1600 and 2L without the #2 and 4 drilling with no harm for years. I also changed oil every week, so no sludge ever accumulated.
Then one day the motor wouldn't accelerate. Found out it dropped a crank plug, and spun the #2 bearing into oblivion. Melted the block-side main, splunged the crank bearing. Welded up the damaged aluminum, line bored the block, replaced the crank, drilled and hex screwed all the crank galleries to replace the aluminum plugs.
Oh, and drilled the block....
You generally don't need the block drilled, until you should have done it yesterday. But if you are going to do it, be sure you go to a VERY experienced Alfa shop that has done this many times, has all the right jigs. Even if you have to send the block a long way. Do the job badly and the block is scrap. I think it's been mentioned that you need special proved bearings, and need to grove the block as well. Also RJ recommends a specific mod to the crank oil gallery(s?)
Last edited by 60sRacer; 10-25-2017 at 02:35 PM.