Bad rust deposits in the block, What is the best way to flush it out

[Rutro]

OK, my mistake was to leave water only in the block for over 7 years and did not drive it....
I was running the motor, everything was fine, got to temperature but very slowly.
I was looking at the water neck and there was corrosion, and thought I would go ahead and replace the thermostat.
Oh my GOD!! there was a lot of flaky rust and looks like the thermostat was messed up. Pulled that out and down in the housing there was a lot of rust, almost look blocked.
Took off the housing from the block.....Oh my GOD!!! Rust crap in the top passages almost blocking the flow.
I opened the petcock on the driver side and it drained very slowly...

I know you can flush the block through the top of the radiator, but I now have these parts off.
Is there a way to flush using the driver side petcock or another way?

Help please, after I kicked myself a couple times my day sucked...LOL

[1 Wild R/T]

Knock a couple freeze plugs out, at least one on each side of the block...... They are the lowest points so the debris can flow out... If you try to flush through the lower radiator hose or any other location the debris has to rise a couple inches before it can escape... Freeze plugs are the best option... 

[jimynick]

   yep, what the man said! AND, if the whole engine is full of rust, just how far before those steel frost plugs start to leak or blow out? I'd do what Wild said and hook a hose into the heater nipples and give it a shot. Replace the plugs with brass ones and good luck. I'd also run a flushing product through once you've got the worst out and look to your rad, because for sure there's going to be some of that ka-ka in there, too. 

[PLY474]

As said...once the big stuff is out, I like Thermocure to remove rust from the cooling system.  https://evapo-rust.com/thermocure/  It will need to be thoroughly flushed out of the block after use.  I removed the lower block plugs to drain and then flush it out with distilled water. 

[Rutro]

Thanks everyone!!! Sounds like it might not be as bad as I thought. Y'all rock!!!
I will try that thermocure.
Your making my Monday start off good.

[Rutro]

OK, another question....
How difficult is it to get the freeze plugs out without removing the motor?
I'm at work so I'm not sure of the accessibility to the plugs.
Now I'm stressing again....LOL

[1 Wild R/T]

The only ones that can't be done in the car are on the back of the heads.... The center plug on each side are both pretty easy, the rear plug on the passenger side is easy... The rear plug on the drivers side you have to pull the starter... The front plugs are behind the motor mounts, they can be done in car but they aren't easy...

If it's a small block there are two inside the bell housing area, you'd need to pull the trans...

[torredcuda]

I had a 360 that overheated, tried flushing it out a couple times and thought I got it as the water was nice and clear but finally pulled it out and removed the rear freeze plugs and there was lot`s of sludge back there.

[Rutro]

Thanks again..
Torred and Wild !!!
This might be a process in stages. Worst case I'll have to go back in and remove additional plugs.

[Chryco Psycho]

I am not sure what the plans are but it may be best to pull the engine & disassemble it & have it hot tanked & cleaned out & reassembled