Shafiroff Racing has a 598" out of a short deck :eek:

what about the merc 9.8 deck blocks 502 415 hp/ 502 500 hp /502 525 hp, I believe all three are the same siamise bore blocks not a bowtie or are the blue bowtie. I have a 9.8 siamise block can that be bored to 4.6 max or under?? thinking about making it into a 540 as my back up to my bowtie 572. cause its been sitting for 3yrs as a 509. thanks

Gen 5 marine blocks are a litle bit thinner than the gen 6. Gen 5 is 1994-95 I believe. Gen 6 is 96 on. Most gen 6 can go 4.600 but sonic checking is always a good idea. They are not as beefy as a bowtie and most builders say they are only good for 800hp or so.