I have a 420a block and head at the shop right now that is currently all ripped apart. It was taken apart for inspection. Motor had good compression before it was taken apart so with new rings I wouldnt see why that would change. The motor spun a rod bearing. The crankshaft, rod, and block is ok. The motor was taken out of comission before it did any serious damage. Just needs new bearings and a set of rings wouldnt hurt. Let me know if you may be interested. I can put it back together in stock form or if you like I can put some nice strong engine parts in it if you wanted.