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jdorour · 03-01-2006, 10:47 AM

The bellhousing, flywheel, and engine mounts are the same.
The 403 uses small port small block heads and manifolds. The 455 uses the large port heads and manifolds. However, the bolt pattern is the same. If you install the manifolds from your engine on the 455 heads you will, at best, have a restriction. I think the restriction would be minimal. At worst you will burn the gaskets if you use the small block gasket set and the small block manifolds on the big block heads. This will cause an exhaust leak. The 455 is also a little heavier.

The factory output rating for a 455 will depend on the year and model you choose. They had a high of 400HP & 510LBS/FT (SAE Gross) to a low of something like 180HP & 200LBS/FT (SAE NET) by 1976. But if you paln to build the engine for use in a boat you can get all kinds of power from any 455.

If you build your engine make sure you tell your engine builder/Camshaft MFG that you are puting it in a JET BOAT as the performance requirements are a little different than for a Prop Boat. AND FOR YOUR SAFETY TRY TO USE AS MUCH MARINE SPEC COMPONENTS AS YOU CAN. I grew up on the water in Connecticut and saw a lot of people get hurt from bilge fires.

Have fun
John

03-01-2006, 10:47 AM	#8 (permalink)
jdorour Senior Member Join Date: Feb 2004 Location: Atlanta, GA. Posts: 123	The bellhousing, flywheel, and engine mounts are the same. The 403 uses small port small block heads and manifolds. The 455 uses the large port heads and manifolds. However, the bolt pattern is the same. If you install the manifolds from your engine on the 455 heads you will, at best, have a restriction. I think the restriction would be minimal. At worst you will burn the gaskets if you use the small block gasket set and the small block manifolds on the big block heads. This will cause an exhaust leak. The 455 is also a little heavier. The factory output rating for a 455 will depend on the year and model you choose. They had a high of 400HP & 510LBS/FT (SAE Gross) to a low of something like 180HP & 200LBS/FT (SAE NET) by 1976. But if you paln to build the engine for use in a boat you can get all kinds of power from any 455. If you build your engine make sure you tell your engine builder/Camshaft MFG that you are puting it in a JET BOAT as the performance requirements are a little different than for a Prop Boat. AND FOR YOUR SAFETY TRY TO USE AS MUCH MARINE SPEC COMPONENTS AS YOU CAN. I grew up on the water in Connecticut and saw a lot of people get hurt from bilge fires. Have fun John __________________ 1966 Ninety Eight Convertible - 425 Tri-Carb, Factory Dual Exh, Switch-Pitch THM400, 3.54 Posi. 1966 Catalina Wagon - 421 Tri-Power, M21, 4.11 Saf-T-Trac, 8 Bolt Wheels 1989 IROC-Z - 5.7TPI