I think the idea is to allow for a more affordable motor available from multiple engine builders.
Whether it's a 525 or a superboat 510CID, if a competitor is going to cheat it will be difficult to police without tearing down motors.
3.9 ENGINE SPECIFICATIONS –
The SUPERBOAT 510 CID Engine will be the only engine approved for the SUPERBOAT CLASS
3.9.1 DISPLACEMENT: Maximum 510 CID, minimum 495 CID per engine, (1020 CID total) with a maximum 4” stroke crankshaft.
3.9.2 COMPRESSION RATIO: The maximum compression ratio allowed is 9.5:1 measured by whistler device calibrated at race site with master cylinder.
3.9.3 VALVE SYSTEM:
3.9.3.1 Number - Two valves per cylinder operated via pushrods.
3.9.3.2 Maximum gross cam lift - measured at the valve is .720 inch with zero lash.
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3.9.3.3 Variable cam timing - is not allowed.
3.9.4 BLOCK:
3.9.4.1 Cast iron - must be approved by SBIP.
3.9.4.2 Chevrolet - design blocks with 9.8" or 10.2" deck heights are approved.
3.9.4.3 Chevrolet - design blocks manufactured by General Motors and World Products (Merlin) are approved. The following part numbers are approved.
3.9.4.4 GM part numbers - 10185049, 10134367, 24502502, 24502500, 12370834, 14044808, 12370833, 10051106, 10237292. World Products (Merlin) part numbers: 080100, 080110, 081100, 081110, 081102, 081112 and 081120. The use of any other block requires the approval of SBIP.
3.9.4.5 Approval - The use of any other block requires the approval of SBIP.
3.9.4.6 Sleeves - or bushings may be used providing the original OEM (GM) lifter bore location is not changed.
3.9.4.7 Pushrods - must ride in the center of the lifter. (no offset lifters)
3.9.5 INTERNAL COMPONENTS:
3.9.5.1 Materials - Crankshaft, connecting rods, pushrods and wrist pins must be made of steel. Titanium or other materials not allowed.
3.9.5.2 Single plane crankshafts - are not allowed. Crankshaft throws must be timed in accordance with OEM specifications. Crankshaft limited to a maximum 4” stroke.
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3.9.6 HEADS:
3.9.6.1 Approved cylinder head - is big block Chevrolet Brodix – 2 PLUS. Only the approved aluminum cylinder heads allowed with OEM specifications.
3.9.7 Valve Work –
3.9.7.1 Spec cylinder head serial numbers - must remain on the head and may not be defaced or altered.
3.9.8 Modifications/Repairs –
3.9.8.1 Using offset head guides or altering the stock mounting location of the head on the cylinder block is not allowed.
3.9.8.2 No welding modifications are allowed to the original head castings. Heads must be returned to Brodix for repair. All repairs will be certified in writing to the SBIP.
3.10 INTAKE MANIFOLD:
3.10.2 Carburetor spacers - or adapters are allowed, maximum of 2.5" between the bottom of the carburetor and the top of the manifold is allowed.
3.10.3 Any stock cast intake manifold. The manifold may be port matched up to 1 ½ inches to match cylinder heads. No fabricated or tunnel ram type manifolds may be used.
3.11 INDUCTION SYSTEM:
3.11.1 Approved Fuel – 91-93 Octane no fuel additives
3.11.1.1 Number - Only one carburetor is allowed per engine.
3.11.1.2 Approved Carburetors - Any Holley Dominator style carburetor is allowed.
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3.11.1.3 Source - Carburetors may be purchased from any source.
3.11.1.4 Fuel injection - is not allowed.
3.12 EXHAUST SYSTEM:
3.12.1 Runner Length/Materials - Exhaust manifolds may be cast or fabricated with no more than 15-1/2" (inches) of individual primary runner length measured at the centerline of any runner from the cylinder head port to the common collector. The overall length includes any gaskets, adapters, or wedges from the exhaust ports to the common exhaust collector. No modifications to the exhaust that increases runner length or give the effect of longer individual runners are allowed. This includes but is not limited to merge collectors, divider plates or turbulence cones. The stock Mercury style 525 CMI header is permitted.
3.12.2 Shape - Any non-divided (common collector), round, square, rectangular or oval, elbow, riser or tail pipe is allowed. The engine exhaust manifolds and pipes from engine outlet to point of exit from hull or deck must be water-cooled by water jackets. The exit from the hull or deck must be located in such a position whereby exhaust fumes cannot affect the crew.
3.13 TRANSMISSIONS:
3.13.1 General: All boats competing in the SUPERBOAT™ class must have propulsion systems capable of turning the propellers in either direction or maintaining a neutral (standstill) state while the engine is running.
3.13.2 Single speed – transmissions / crash boxes capable of forward, neutral and reverse are allowed.
3.13.3 Multi speed - transmissions are not allowed.
3.14 LUBRICATION (ENGINE):
3.14.1 Wet sump - and internal oil pumps are allowed.
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3.14.2 Dry Sump - External oil pumps or dry sump systems are allowed, however, a maximum of three scavenging pump sections allowed on dry sump systems.
3.14.3 Intake valley – must remain as cast with NO alterations to prevent oil flow from the valley to the crankcase. No raised sections may be attached or formed with any material around oil drain openings in the intake valley. No “damming” or collecting of oil by any means is allowed in the intake valley.
3.15 IGNITION:
3.15.1 Distributor - must remain in factory delivered location.
3.15.2 Electronic ignitions – Engines are required to use the MSD Digital ignition system with 7000 RPM limiter.
3.15.3 Crank triggered and belt drive ignitions - are not allowed.
3.15.4 Coils - Ignition systems are limited to one (1) ignition coil. Individual ignition coils per cylinder are not allowed.
3.15.5 Back up ignition systems – Are Not Allowed.
3.15.6 Spark - must be distributed via distributor rotor and cap.
3.16 ENGINE SUPPLIER -
3.16.1 SBIP also will allow multiple engine builders to supply engines that meet the SUPERBOAT™ engine specification.
3.16.2 The goals of the SUPERBOAT™ spec engine program are to:
3.16.2.1 Increase competitive balance throughout the fleet
3.16.2.2 Develop a “5 race engine”
3.16.2.3 Reduce maintenance and operating costs for the majority of the teams during an entire season