I was wondering how to flush the block on my 74 xj6, I recently took off the head for an upper engine rebuild and all the coolant passages on the block seem to have a lot of rust and dirt. Should i just put a hose in a passage and let it spew out of the Welch plugs or something, need some help, thanks

 

If you try to flush the block with the head off, you cannot use high pressure. All the muck will come up the water passages, fill the cylinders and get in the timing case.
Low pressure dribbling will remove very little if any. Whether you can properly block all these openings - I don't know.
I removed my complete engine from the car. Water pump off, inlet manifold off, exhausts off, trapezium plate off at rear of block, three core plugs on top of head removed. All welch plugs out. Ports plugged.
High pressure washer in the welch plug openings. A river of sediment and muck flowed down my driveway. I am confident I got the lot out.

 

Agree with The Mekon. Not easy or effective with the head off or the block not fully stripped. I generally crunch up a dishwasher tablet and chuck it in with the coolant for 15 mins. It helps to breakaway the crud before draining and finally flushing through with a garden hose. You can then pull the welsh plugs and flush again.