I acquired a stock bore 4-bolt main 511 casting engine from a junkyard. I was also concerned about building on this block foundation from what I have read from others here, so I took it to Greg Stafford at Stafford Performance - Car Parts Machine in El Paso Texas, who is a top notch circle track race engine builder. I asked him to sonic test and magflux this see if there were ANY questions about it's ingerity, and his honest opinion about using this block. He frowned and squnted a bit at first, but said he would investigate it thoroughly. He called me after investigation and told me that he finds this to be a good and solid crack-free block that will go .030 overbore and would have no concerns building this for himself for racing. I then had him plug the steam holes and do all the decking and machining he would do for a complete "race-prepped" block. I then had him balance a 392 rotating assembly I already had (4.145 bore x 3.625 stroke x 6" rods) with very small dome slugs. I asked him to keep compression mild to prevent any wall fractures or overheat problems. He machined and rebuilt my 64cc World Product heads, which left it just under 12 to 1 compression. I have run this engine HARD many times at up to 8K rpm on a flat tappet (JR109) cam and have never got it over 170 degrees on alcohol. Of course alky keeps things cool, but I have zero concerns for this package. I guess maybe I just got lucky, or maybe it is a calculated risk by asking an expert his honest professional opinion if it is worthy or not.