Biggest stroke crankshaft you can fit into a mark 4 and 5 block? Also will a mark 5/6 block take the large over bore like the mark 4 blocks?
I want to fit a 4 3/8 or 4 1/2 stroker crank in a 454 block

Thank you
Bill

Bill I have read(thats all I can offer but have pondered the same question)In a 427/454 BB a 4.25 should fit. No one has tried a 4.375 that I know of here. No-one here thinks a 4.5 stroke will work without serious massage and possibly repairing an oil passage with a copper tube kit.
as far as bore goes I believe all the post mark 4 blocks are of a siamesed wall bore casting which means they can tolerate larger bores than Mk4. I would love to know for sure from someone myself. so if you try it please post outcome. Oh and try a search for more info. Good luck.
Milan