Hello! Probably a dumb question, but...Why do some big blocks have coolant passages that are "O" shaped and some that look like a sideways "8". I'm talking where the head gasket seals. Laying the head gasket on the block, looks like the "O" style has almost no flow opening. I have 2 blocks side-by-side and just noticed this. Which is better? Or am I overthinking this lol! Thanks, Jeff

The "oval 8" holes are for better cooling.Here's link to info about big blocks:
440 block info

I would highly suggest drilling a 1/2" additional cooling hole between cyls 3/5 and 4/6 on the outer (outside) edge between the 2 head bolt holes to form a triangle. Punch do not drill a hole in the gasket and drill a matching 1/2" hole in the head(s). This a very hot area (between 2 ex valves) & needs the help. I would also drill the existing outer holes to at least 3/8" and add some at the end of each bank. No downsides to this & just need spacial awareness for how much surface area is available to you to work with EDIT and how close you are to the edges/cyls (drill a small hole 1st & look inside)

Hi Guy's! Didn't get a chance to thank ya both yesterday. So, Thank you! Still find it odd that the head gasket has such a small "slit" in that area for the water to flow through. If the block passage is that big, how come the gasket is so small?? Take care! Jeff

yes open them up either with a gasket punch set (HF has em for less than $10) or exacto knife/razor blade just dont drill em or it'll grab the gasket & shred it