Okay... Final update to this version of the block.
Sealant is dry, Y connectors are done and system was upgraded without a hitch.
Did do some head scratching as to how to plumb this.
Here's the block in action... Water is murky from when I reversed the loop flow from pump-blocks-radiator to pump-radiator-blocks. I will be changing the water soon to distilled as I didn't have enough on hand to do this with.
Another shot of the whole system... even got part of the old waterblock in the picture.
My system temps went up after this... and I got to thinking "Now why the heck would that happen?"
Turns out that the block IS more efficient at getting the heat into the water... so much so that it made me aware of the fact I don't have enough moving air directly across my radiator. So I put a couple of 120mm fans across it and WHAM... my temps dropped by 7°C from my former average! WHOOT!
Now I think I will be revamping the ducting for the radiator box to maximize flow and lower the speed slightly of those fans or get quieter ones with better CFM flow.
Thanks to all who helped me rough this out in the beginning.
Thanks to BladeRunner to inspire me to play with my mill again.
After the ducting changes and some statistics taken on average temps (yeah, yeah, I know ... sucky accuracy & linearity) I'll make a smaller jet block and compare them.
I might throw in a couple of HDD blocks in the mean time to tax this radiator further... whaddya think?
:shrug: