Afton Motorsports Park Modified Engine Rules

The Modified engine rules for Afton Motorsports Park are listed on this page.


[BIG BLOCK-BIG SMALL BLOCK (OVER 358 CD) ENGINE SPECIFICATIONS] [Engine] [Carburetor] [Intake Manifold] [Cylinder Heads] [Camshaft] [Pistons / Rods / Crankshaft] [Ignition] [Lubrication] [Fuel]

Page 2 of Rules: [Go to Page 2] Includes 358 Modified Engine Specifications: Engine, Blocks, Cylinder Heads, Crankshaft, Rods, Pistons, Vibration Dampners, Camshaft, Intake Manifold, Carburetor, Ignition, Lubrication System and Fuel

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(Afton Motorsports Park allows various engine combinations. This is a guideline for the more popular).


  1. Any cast iron block.
  2. Only normally aspirated engines are permitted.
  3. Maximum displacement of 467 cu.
  4. No reverse rotation engines.

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  1. 1 - 4 barrel carb.

Intake Manifold:

  1. Optional as to design or manufacturer, but the manifold must allow for the mounting of only one 4 barrel carburetor.

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Cylinder Heads:

  1. Any 2 valve per cylinder head.
  2. Optional as to design or manufacturer but must be made of cast aluminum or cast iron only.
  3. Valve sizes are optional.
  4. Any form of porting is permitted.
  5. Titanium valves and retainers are permitted.
  6. No hollow stem valves or liquid cooled valves are permitted.
  7. Only 2 valves per cylinder are permitted.
  8. Only one spark plug per cylinder.


  1. Optional as to design or manufacturer but camshaft must be in block in stock location.
  2. No overhead cams are permitted.

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Pistons / Rams / Crankshaft:

  1. Any 3 ring piston, any steel rod/crankshaft - no titanium.


  1. Any kind of ignition is permitted, as long as it is mechanically driven in the stock position.
  2. No crank trigger ignition systems are permitted.
  3. Only one ignition coil and one ignition box (amplifier) are permitted on the car.
  4. Only one spark plug per cylinder is permitted.
  5. Traction control devices are not permitted. Traction control devises that use the brakes are also illegal.
  6. Ignition boxes must remain as manufactured with no internal or external alterations. NOTE: Ignition boxes may be swapped or confiscated by Speedway at any time.

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Lubrication System:

  1. Conventional or dry sump may be used.


  1. Only racing fuel or pump gas is permitted - small block under .360 C.I. can run alcohol.
  2. No nitrous or any other additives are permitted.
  3. All fuels are subject to random testing at each track.
  4. No electric fuel pumps are permitted.

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