I did the same modification to my block whn i built my 360 based stroker. I havent had the timming cover off yet to inspect anything, but the motor still runs!
I just want to know if is necessary. My engine is going to have 10,7:1 CR, aluminum heads, fuel injection from FUELTECH (model FT200), M1 Mopar Single plane with 1000cfm Holley TBI and TTI headers. So it will get some performance. Its necessary?
I have to call BS on the info posted as attached image above.
Only a certain amount of oil is going to cling to the chain.
Excess oil will just sling off.
Prove this for yourself with any bicycle and a quart of oil.
You might even get a pan full of foamed oil in your engine.
I don't know how one can rely on the tiny holes not plugging up. I don't quite follow the design theory. With the thrust plate on, won't oil just dribble down the side to the bottom of the pan without even touching the timing chain? I think more important is to get the latter "drip plate" that installs over the thrust plate, with a finger in the upper left "missing bolt" hole to dribble oil down onto the timing chain. I got one for ~$10 at a dealer.
This mod will foam the oil. Its very little so its not going to hurt anything. Its a small hole and very little oil is going to go thru it. The main benefit to doing this is not to provide more oiling to the chain, but to keep it cool. Its not a bad idea. you will have to drill a hole in the thrust plate as well.
The drip rail that is behind some timing covers just gets drainback from the lifter valley and lets it drip on the trailing side of the chain. Some dont even have this part. Early ones used a hollow bolt.