502....

I'd actually like to see the hp500(502) vs the hp450(454) in a dyno comparison.

I myself, probably would not let this debate decide on which engine will last longer. If you are building from scratch, then yes, go for the 502.

Ive known marine 454's of all different hp variations, to last from 500 hours to 2000 hours. Its all in maintainance and conditions they were used. Like stated, they both use a 4" stroke and 6.135 Rod. They are very similar from a design standpoint.

48 more cubic inches means close to 48 more lb ft of torque. Since they both weigh the same it doesnt make sense to have less torque and 30 less horsepower in the same package now does it?

The bigger bore is the best benefit of the 502.

I agree. The bigger bore helps unshroud the valves, which means more airflow/hp.

I call B.S.

Given identical builds and compression ratios, the only way the 454 mag would ever make similar power than the 502 mag is if the intake being used was physically maxed out on flow with the 454, and even then the 502 would still have noticeably more torque and acceleration.

The cubic inch difference in the two motors is not the only reason the 502 makes more power, the other reason is that the bore is larger, thus unshrouding the flow from the valves where the 454's smaller bore requires bore notching to deliver equivalent results.

For the life of me, I can't think of a single situation where the stock block 454 would be the preferable choice over the stock block 502 unless you were running more than 20 lbs of boost and wanted the additional cylinder wall thickness to aid in stability of the block (but then we're still talking about if you were using a thickwall 454 block, not a thinwall passenger car block).

Rotating mass in the 502/454 comparison is a complete NON ISSUE in the sub-5,000 rpm world of 500 horsepower marine engines. The forged components used in the mags are plenty beefy that the only way you'll have excessive bottom end wear in either one is if you have a serious oiling malfunction.

MC