ddez

Not sure about the reversion, but it wouldn't surprise me if that was the case. Based on the information the previous owner provided, it sounded like the engine was overrevved.
See my post above to Griff, I'm replacing the stock log style manifolds with Revolution Marine manifolds.
If I decide to go that route I will definately be contacting Bob

Griff

The RM exhaust is a good low budget upgrade. I doubt you will be able keep the Qjet. the intake may be ok. I'm not sure what comes on the 400.


I another guy specs I used when I hopped up my 454mag. He used the cam I posted and did a few other mods. He dyno'd at 42hp @ 5000 rpms. Probably could have pulled 440-450hp with some more rpm. Here's one of the threads.

http://www.offshoreonly.com/forums/s...ighlight=Griff

KAAMA

iTrader: (1)

As an interesting expample of a 454cid marine engine.....about 5-6 years ago my cousin modified his Merc 330hp engines and used an off the shelf flat tappet hydraulic cam...218*/226* on 110* lobes, old semi open chamber oval port GM heads that he had JimV install 2.19" intk/1.85" exhaust valves and did some bowl/shortside radius porting, Holley carb on top of a dual plane aluminum hi-rise intake manifold, bore notched the cylinders for better flow around the valves, 8.6 comp ratio and made 461hp @5100rpm on Tom Earhart's dyno with car style tubular dyno headers. The engines made 510 ft. lbs. of torque @3600rpm.

He installed the engines in his 1988 32' Baja with GIL exhausts (dry), went from a 21" prop to a 25" prop and picked up at least 10mph in the midrange cruise speed and on top.