Gooked up Cooling system

[Jason Ball <madmac@domain.elided>]

I am in the process of reassembling a my parts car's 2.5L V with the intention
of installing it my Milano.   This motor had not been well cared for as
evidenced by a tremendous build up of "gook" on the water jacket in and around
the piston liners.   In fact there was so much gook in there that when I tried
draining the coolant nothing came out until I pounded a screwdriver into the
drain hole and broke the gook up enough for the coolant to pass.  

The gook is a white chalky build up that will scrape off with some difficulty.
   I assume it is either a calcium build up from the use of non-distilled
water and a lack of coolant flushes OR I suppose it could be a sign that motor
was overheating and cooking the coolant.

Either way it seems the gook will act as in insulator and needs to go.  I
would like to attack the gook chemically so that I can remove the gunk where
it can't be seen or reached. I've seen products that are ment for this
purpose,  but they warn against use on aluminum.   I've tried vinegar and some
citrus based cleaners both to no avail......  

So my question is:  What should I use to dissolve this gook without damageing
the block or liners?  

Thanks again for everyone's advice and encouragement!

Jason Ball
Austin Texas

87 Milano <waiting for motor>
2.5l <170k & stuck heads>
2.5l <gooked up @ 101k>
85 Subaru 4wd Wagon <AC works!>
91 Novara Arriba <keeps MY cooling system flushed>

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