Oddball stroker question

The bilge as it sits now, I still have to glass in the new diagonal stringers, hopefully Tuesday when it warms up some.

Knowing virtually nothing about marine engines...what is the round beasty in the middle of the two engines?

That's the flame arrester, it normally sits on top of the carb.

If you go with the magnum engines you'll need different flywheels or have your current flywheels rebalanced to magnum spec. The difference isn't much but it's enough to cause a vibration especially at high rpm.

daliant said:

If you go with the magnum engines you'll need different flywheels or have your current flywheels rebalanced to magnum spec. The difference isn't much but it's enough to cause a vibration especially at high rpm.

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That is not a problem, I am going to change pistons wether I go stroker or not, so balancing is going to happen either way.

Getting 400 to 450 N-A, reliable, crank hp,from 400ish cubes, to run WOT @ 4400 for extended periods, and idle smooth at 750rpm, is going to get really, really, really expensive.

That was the bad news.
-Heres the good news;Forget; the 750rpm idle and the 4400rpm peak power,and that cam, and the 9:1c/r.
- Firstly,will your outdrives and props support more engine rpm?
-If no, I see supercharging in your future(not a bad thing).
-If yes;youre going to need more engine rpm. Probably 5400 with 400ish cubes. Then you work the formulas backwards as to headflows,camshafting,Dynamic C/R, and finally Calculated C/R.
-Then you find somebody to build it, so it will last.
-This requires professional helps and gobs of cash.
-And I would not mention anything to the professional builder about a budget. Budget motors blow up.
-Now, getting back to supercharging. Somebody remind me: Just how many guys here have pulled 400 hp-plus, out of a bone-stock 5.2l/318s. Now, since you have the 5.9s, 450 is pie.Maybe even at 4200rpm. NO; fancy heads,big cams,expensive porting,C/R manipulations,outdrive gearing,re-propping,etc. And if the engine blows, heck, keep spares with all the cash you saved.And bonus they idle at 750 or even less.
-Thats what I would do.Uber duper Supercharging.

If it was me I'd go with forged cranks. Marine is a bit harder on the cranks and the cast 360s survived more because they probably weren't run that hard. I'd also run factory iron heads. Have the heads done for performance and they'll make the steam you want. Run a dished piston to keep the static compression down. Run a good rocker setup - I'd do sintered iron rather than aluminum for durability.

Sell me one of those blue 4bbl intakes...

Ill sell you an intake for 25$ plus shipping, but it has a lot of corrosion in the water passage up front, and may need some repair.

As to the compression and cam choices are pretty limited, It has to run under heavy load for extended periods on crap gas, and a bigger cam is a no go due to water reversion with a narrower CL or more duration. I can spin the motors up to 5500 MAX but will prop it so they max out at 5000 or so. 383 Chevy motors make 450 HP withing the same constraints, so I figure a 408 with decent heads should be the same, especially since a stock 360 Magnum can make 300 with a M1 dual plane and a stock cam. I cant imagine I couldn't make another 100 to 150 with a bigger cam, a blueprinted true 9 to 1 compression, a better intake, and better flowing heads.