ironhead,
"Safe" is a relative term. Compared to what? We rev our pump gas "street" engines with the Eagle (3") crank to about 6,600 regularly. Rick Holladay revs his 4" stroke 3.25" main 440 to 6,800. Scott Roberts revved his 406 to 6,600 with the hydraulic cam, and to 7,200 with the solid. The Drunken Injun (3" main) revs to 8,800. With the exception of "DI" (only 3 passes on it so not enough "hard" data), ALL of these engines are racing and driving for more than a year or two without refreshing.
RPM is more a function of head flow and valve train than it is "bottom end". You do, of course, need high quality parts in there. The "weak link" in a stock engine is the connecting rod. They gotta go! Rod bearing "speed" is another area that can use some attention. IMO, the only real drawback to the larger main journal, aside from the weaker block (NOT insignificant), is the added heat it puts "in" the oil. I would think that's only a big issue when high RPM is used for extended periods.
It is commonly believed a 455 crank is stronger than a 400. True enough. But again, measured against WHAT? The main journal in a BBC is 2 3/4". So is a Hemi. Those cranks are plenty tough, so the added 1/4" of diameter in a "large journal" Pontiac is not necessary. The crank in a 400, even a "stroker", is far stronger than the block.
Jim
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