Mopar Action On-line – Tech Questions


Tech Question

Rob C, Oakland, CA, 340

There is an argument raging about rpm limits on 340’s withstock two bolt mains; some say 8200+, and while never saying never, I’d haveto see some more hard data before I’m a total believer.

Care to weigh in with your opinion?


It’s not that easy. Lots to consider. Just at a glance…

First of all, reciprocating weight factors in. And, to an even largerextent, so does HP production. Much over 500-550 HP, the cylinder wallssplit open (unless the jackets are filled with concrete.)

Then there’s the bizarre pushrod-to-lifter angle deal. Wanna get scared?Look at this running on a Spintron with a strobe lamp.

Sure, say one guy spins his to a bazillion RPM and it hasn’t blown up (yet.)Even if true, that’s not really hard data. You’d need a heavily instrumentedblock measuring deflection, etc. And/or empirical evidence of HUNDREDS thathaven’t blown up.

Bottom line: The factory usually said 72-7400 was max. I concur. Even then,the bottom end had better be right.



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