Silver Wraith 8.1L 430bhp

V8 Small Block Chevy 496cid

8.1L 430bhp V8 Performance Marine engine rebuilds Having stated that Swaymar prefer the bore and stroke ratio of the 496 cid, why do a 502? Simple. We want to be able to offer all boat owners the benefit of a Swaymar engine and recognise that there are owners out there who do own 502's that need rebuilding or upgrading. By careful port matching, combustion chamber re-shaping (as for all our engines) and by using the same specially developed cam profile as we use in our 496 we have been able to obtain the same peak 430 BHP at just over 4800 RPM some 400 RPM further down the band than a standard 502. While not quite as fuel efficient as our 496 cid in larger heavier boats (over 35 ft). Fitted in a smaller or lighter boat there is very little difference between the two.

Get a quote today

8.1L 430bhp V8 Performance Marine engine rebuilds


  • Mercruiser
  • Volvo Penta
  • Indmar
  • any boat running Chevy V8s

Whilst fine on Volvo Penta Duo-prop legs, in Mercruiser applications it is recommended not to use legs of less than Bravo 2X or Bravo 3X specifications.


All of our engines include a free inlet manifold inspection and reconditioning to 'as good as new'.
Note: If prior to inspection your existing manifold is un serviceable, a new one will be required.

  • Fresh water cooling system
  • Stage 1 performance marine camshaft
  • Full refurbishment and re assembly of existing ancillaries


Most but not all engines that are sea water cooled will require a new block upon rebuild.

  • Re-manufactured block
  • Brand new block


  • 1 year limited warranty,subject to the fitting of a new or refurbished inlet manifold and new cast iron exhaust manifolds
  • 2 years limited warranty when fitted with 1 piece stainless steel exhaust manifolds

Not Included

  • *New Cast iron exhaust manifold*
  • *New Inlet manifold*


Performance Marine engine rebuilds We strongly recommend to all of our customers to consider trying a 1 piece stainless exhaust system and do away with the fear of leaky cast iron ones ruining your engine. You can find more detailed information on stainless steel marine exhausts as well as independent articles written by marine surveyors on the pit falls of cast iron manifolds at

Propeller Pitch

V8 Performance Marine engine rebuilds Depending on boat, in order to prevent over-revving, and feel the full effect of its extra torque, this engine may need to carry a larger diameter or coarser pitch propeller.

Get a quote today


Displacement 509 CID (8.3L)
Engine Type V8
Peak Torque 540-550 ft lbs @ 4200 RPM
Torque Range 510+ ft lbs @ 2600 - 4700 RPM
Bore & Stroke 4.500" X 4.000" (114.3mm X 101.6mm)
Compression Ratio 9.5:1
Camshaft Stage 2 - Specially developed marine camshaft - delivering more torque at lower rpm.
Major Components Steel crankshaft, forged competition con rods, and performance pistons.
Head & chamber work Moderate reshaping of combustion chambers and cylinder heads - Improve gas flow and increase torque.
Cooling System Closed fresh water cooling, Long Life 5-Year Anti-Freeze, 20 year long life silicon hoses - Protecting your engine from the inside out.
Advanced Engine Lubrication System Expertly modified oil galleries provide greatly improved lubrication to the camshaft, cam followers, gears and timing chain - For optimum engine longevity.
Dimensions (LxWxH) in 43x 30 x 22
Dimensions (LxWxH) mm 1092 x 740 x 559
Weight (lbs./kg) 948/431
Get a quote today