Re: causes for cracked blocks?
I had my 7.4 sitting on an engine stand when I installed the closed cooling system.
I removed ALL of the soft plugs (AKA "freeze" plugs by some uninformed people)
I noticed that the water jacket had about 1-2 inches of rust flakes and sand at the bottom of the cooling system . So much so that on one side the sand was well above the drain hole.
Poking a wire in there didn't produce any additional water until I was able to get all the sand and debris out.
With all the soft plugs out I was able to see in there pretty good and was able to flush ALL the sand, rust and other debris out of the cooling system. THERE WAS A LOT....more than I would have expected. It's VERY common to have sand and rust covering the drain holes to the point that a wire doesn't get it all out.
You MUST ENSURE that all the debris is out of an engine that you are draining.
I would take it a step further and run the engine with the out-drive in a bucket or tub with a gallon or 2 of anti-freeze in it long enough to ensure that the thermostat is open.
Even though i have closed cooling I still did this to ensure that the drive, raw water pump and associated plumbing has a 50/50 mix of AF in them.
Cheers,
Rick
On a 7.4L engine. How much water will come out when draining the block? On mine the left side block drained alot and the right side only trickled(yes I used a coat hanger to see if it was plugged up) ALot comes out of the manifolds/risers.