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I dunno if you guys are into boats or already know, but Mercury gets its 496 blocks from GM, and I'm just wondering if anyone has thought about swapping parts with marine parts, since they are built for much more demanding use and higher horsepower.
 

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I dunno if you guys are into boats or already know, but Mercury gets its 496 blocks from GM, and I'm just wondering if anyone has thought about swapping parts with marine parts, since they are built for much more demanding use and higher horsepower.
I have a 496HO (High Output) in my boat. 425hp at the prop.

All it is really, is the ECM and the camshaft. The short block is the same / as are the heads. My HO has the same small valves and weak springs as your pickup. The 375hp version (straight Magnum) is only a cam and ECM change from the HO.

The intake, coils, throttle body, everything is the same as your pickup.

Some head tweaking (big valves, cleanup porting, and good springs) and a Comp cam or Crane replacement would be real nice for a pickup. Run a programmer and some more fuel pressure and you would be around 450hp with a decent exhaust.

I have some 1.75 Scorpion roller rockers waiting to go on. This will bump my valve lift up and free up HP from the friction of the stock rockers (engine will then be FULL roller). I will install BeeHive springs at the same time to lighten the valvetrain and improve efficiency.

There are plenty of tweaks for the 8.1
 

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Pa32 have you been inside one of the marine engines?, reason I ask is I read in Boating mag that marine used forged steel crank and double row timing chain

May be mistaken again but doesn't the BB use 1.8 rockers? Or did GM drop to 1.7's?
 

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Pa32 have you been inside one of the marine engines?, reason I ask is I read in Boating mag that marine used forged steel crank and double row timing chain

May be mistaken again but doesn't the BB use 1.8 rockers? Or did GM drop to 1.7's?
No, have not had personally torn one down yet. I have seen as set of heads on a workbench, though. They had the standard stamped rockers (1.7 as BBCs have always been) and the non-adjustable studs/nuts. They already have guideplates, which is good.

Standard Gen-VI conversion studs work fine for the valvetrain. ARP has a part # specific for the 8.1, though.

Yes, forged crank, per the Merc manual. Cast pistons are the weak link for over 500hp.

I would fully expect to see a double-roller chain, as marine is alot of sustained RPM use.

1.8 rockers would be real close to valve-to-piston limits with the HO cam.

Tbyrne here used to sell the Raylar stuff, or still does, and had a very warmed-over 8.1 in his pickup.
 

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Jeez I knew better on the rocker ratio (note to self... stay away from posting at 2:30 in the AM)

My 8.1 is still bone stock, hopefully sometime in 08 I'll warm it up a bit, thinking about a cam and the neccessary ECM mods, probably not mess with the exh much unless really needed. I think there's a lot left in the tank vs. stock... 496 cubes should have no problem pumping 500 HP and boatloads of torque
 

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Jeez I knew better on the rocker ratio (note to self... stay away from posting at 2:30 in the AM)

My 8.1 is still bone stock, hopefully sometime in 08 I'll warm it up a bit, thinking about a cam and the neccessary ECM mods, probably not mess with the exh much unless really needed. I think there's a lot left in the tank vs. stock... 496 cubes should have no problem pumping 500 HP and boatloads of torque
Biggest gains, initially, have been on the exhaust side. Personally, I would get the airflow optimized on the outside before going inside. Changing the cam would not be near as usefull if it had to smack against the stock exhaust. Also if it couldn't pull the air through the intake.

After that, the cam and ECM would be your ticket to plenty of power.
 
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