408 build Horsepower estimates

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murfman

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I am building 2 408 Cu IN Magnum based engines for my boat, Here are the build specs:
Scat Cast 4" cranks,
Scat H beam rods W/ ARP 2000 bolts,
Icon 983 forged pistons,( should work out to 9.2 to 1 compression),
Hughes SER 1828ML-14 cams,
ported Enginequest Magnum heads with 2.02 intakes 1.62 Exhausts,
Edelbrock Performer RPM Air Gap intakes,
Edelbrock 750 CFM Marine carbs.
Exhaust will be the Chrysler marine late style center rise manifolds/risers with 4 inch thru hull exhaust, no mufflers.

The short blocks are built, and the heads are at Rad Racing right now, when they are done I will be having them broken in and run on the Dyno before I install them in the boat, just wondering how much HP you guys think this combo will make? I too am wondering, and wondering how much of a handicap the marine exhaust is going to be.

Cam card:
 
M-m-m-m-oney!

I have a similar cammed 360, since the extra cubes add about 50hp/tq I say. 400hp/450lb tq.
 
Paired boat engines should have one of them rotating the opposite direction. Assuming you did so, curious to see if they both make the same power in opposite directions.....
 
Don't let Hughes sale you those piece of crap PRW rocker arms. Absolute junk!!
 
mopowers said:
Depends on who's dyno you put it on.

Why such an anemic camshaft?
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Marine application, motors run under full load all the time, boats do not coast or freewheel, and the maximum RPM they will see is about 5000 RPM. In a marine application a cam with too much overlap causes reversion sucking the water that is mixed with the exhaust back into the combustion chamber. I am borderline with these cams.
 
ragtopfury said:
Paired boat engines should have one of them rotating the opposite direction. Assuming you did so, curious to see if they both make the same power in opposite directions.....
Click to expand...

Not on stern drive applications. The outdrive takes care of the prop direction. On the Volvo drives you actually flip the shift lever so one is in forward and one is in reverse when each shifter is pushed forward into "drive". On inboard and V drive boats they used to run reverse rotation motors but they don't do that much anymore.
 
Woods74 said:
M-m-m-m-oney!

I have a similar cammed 360, since the extra cubes add about 50hp/tq I say. 400hp/450lb tq.
Click to expand...

That will be a nice upgrade from the 250 HP 340 SuperBeeIII engines it had. It will be like adding a 3rd motor lol
 
There is also ultimate prop speed correct?
IMO, I think it will be a strong runner but I give no HP guess. I think the accurate result will be a nice smile.
:D
 
that boat will haul *** let's hope the gear box will handle the extra torque . you will notice a big improvement in out of the hole to plane and top speed
 
jimjimjimmy said:
that boat will haul *** let's hope the gear box will handle the extra torque . you will notice a big improvement in out of the hole to plane and top speed
Click to expand...
Updated the outdrives to Volvo SP-A drives, as long as I keep the props in the water I should be fine.
 
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