WD's, and WD-45's usually crack at the bottom--at the web between the 1-2, 3-4 sleeves... This web is very narrow..(I guess because of many years of boring to make them more powerful over the years of development).... I would guess that at least 60% of them are cracked....I always figured it was from stalling a hot engine, and not staying with it, and turning it over, until the pistons have a chance to cool some--causing the sleeve-bottom to swell, and crack the web... If that is where the leak is, it could also be the lower sleeve packing rings... Many posts have been made about this... Many times, you can avoid an overhaul by removing the head, cleaning the inside of the block real clean, and carefully pouring a Pint of Permarex-type non-hardening Aviation sealer in the lower water jacket, coating all bottom surfaces...this has worked well for me...!!!! Otherwise, you will have to have the block "pinned, and welded"...it is hard to find a block with no lower web cracks...!! They can run for many years of heavy use with these, and be fine...
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