My take on the oiling system crossover tube for the small block

"Velocity"? "Slow the flow so it doesn't blow past the passage"?

Assuming the basic first step of a tube or bushings - sealing up the right galley at the #1 saddle (plug the left galley feed), and providing a sufficient pressurized feed to the front of the right galley should eliminate any "oil rushing past the passage" issues and deadhead the oil in that galley with no where for it to go except to the mains. The oil to the cam bearings is easily controlled so that the mains receive the full benefit of this supply.

Creating another "leak" to slow the flow doesn't make sense. Years ago, when I first tackled this, a picture and explanation of the crossover left me scratching my head.

A quick look at an OE cast 340 crank shows the mains having a single hole for each rod journal. These holes are drilled straight through the crank and as a result, the passage lines up with the feed in the main saddle when the rod journal is very near BDC. A quick look at the information from several aftermarket crank companies shows they are also using "straight shot" rod oiling as the best method. I do not have any of those cranks here to look at to see how they are clocked, but it appears the only real way to ensure 360 degree oil the rod is by using a full groove main bearing - and keeping the right galley full of solid oil under pressure.

A quick search shows conversations about problems arising from crossdrilled cranks where the passage is not a straightshot through the crank at high RPM. And the use of 1/2 vs. 3/4 vs. full groove bearings being a balance between relative surface area and oil supply to the rod. This quote sums it up "It's surface area of the bearing versus "clock time" of oil sent to the rods. Pick your favorite based on the comparative demands or likelihood of failure based upon testing or experience."