From: Walt Fricke
PCA Club Racing Rules and Tech Coordinator

SP911 2018 Update 1/25/18

Replaces SP911 rules in 2018 Rule Book, version 12.15.17

This class is for 911s with air-cooled 3.0L and 3.2L engines. Note for 2018 – SP911s which were raced with PCA in 2017 with a 2.7 liter engine may race in this class in 2018 under the engine rules and weight contained in the 2017 rules, but that engine is phased out of the class entirely as of 2019. Modifications not specifically listed below are prohibited. Where “stock” is specified, it means the components must remain stock. No material can be added or removed; no re-allocation of weight or material can be performed. No material can be substituted for another material of similar geometry. PCA will honor approvals of modifications of items not in compliance with the rules if the approval has been noted in a vehicle logbook. PCA Club Racing will honor prior written approvals of modifications not listed here by the sanctioning body from which these rules originated.

  1. Chassis, Body and Interior
    1. Any Porsche 911 chassis up to 1989 is allowed except for turbo or turbo-look body shell.
    2. Bolt-on fiberglass and composite replacements of front and rear bumpers, rear deck lids/tails, front fenders, and front hood are allowed. Bonded or glued fiberglass or composite sunroof “plugs” and fender flares are allowed. Fiberglass or composite rear fender flares may include most of the rear fender as long as steel remains around the perimeter of the fender. Substitution of other parts is not allowed. Fender flare configuration is free.
    3. Cars must have a windshield, a rear window and rear quarter windows. Cabriolet bodies must have a stock size windscreen and no other windows are required. Materials may be original equipment or equivalent glass, polycarbonate, or other break-resistant plastic.
    4. Rear wing choices include: ducktail, 911 whale tail, 930, IROC, large IROC, 911 3.6 RS wing, 3.8 RSR short wing. Wicker bills up to 1″ can be added to the ducktail, 911 whale tail, 930, IROC and large IROC tails.
    5. Any front air dam may be used as long as it does not extend forward of the stock front bumper (excluding bumperettes).
    6. Interior modifications are free.
    7. Electrical system and instrumentation is free.
    8. External lights, including brake lights, are free, but at least two brake lights must be in the stock fender locations and at least as visible as stock lights.
  1. Engine
    1. All engines must run on standard pump gas with octane rating not to exceed 93.
    2. Exhaust system may have any header system with a maximum primary tube size of 1.5″ outside diameter. The 3.2 liter motors may increase the primary tube size up to 1.625″ OD.
    3. Crankcase can be any 911 crankcase and machining of any kind is allowed.
    4. Rods must be stock. Aftermarket rods bolts are allowed.
    5. Valve springs & retainers are free, but all engines must have a functioning rev limiter set at no higher than 7,200 rpm.
    6. Ignition system is free as long as it is single plug per cylinder.
    7. Engine oil system and cooling is free.
    8. Fuel must be street car pump fuel and no higher octane than pump premium readily available from gas stations in the state in which the race is head, or adjacent states if they are at a distance reasonable for hotel accommodations for the event. No race fuels, additives or mixing allowed.
    9. 3.0 liter engine specs
      • Allowable intake systems are: 40 or 46 mm Weber or PMO carbs, CIS intake manifold from any year and with any fuel injection system, Bosch low butterfly MFI from 1969-1973, 3.2 intake manifold with any throttle body and airflow meter, “straight-through” fuel injection systems with individual throttle bodies no larger than 46 mm (e.g., TWM, Jenvey, etc.), 3.6 intake manifold from 1989-1995 911 with any throttle body(s). Slide valve intakes are prohibited.
      • Crankshaft: stock 70.4 mm stroke with 9 bolt flywheel configuration.
      • Pistons and cylinders: any stock CIS 911 SC 95 mm bore. Replica pistons from Rothsport Racing are allowed. Maximum compression ratio is 9.8:1.
      • Cylinder Heads: maximum port sized of 39 mm intake, 35 mm exhaust and valve sizes of 49 mm intake and 41.5 mm exhaust. Small intake port 3.0 liter heads may have cylinder head material removed to match the port shape and dimensions of the large, stock 3.0 intake port.
      • Camshafts: stock 911SC.
  1. Transmission and Clutch
    1. Models up through 1986 must have a Porsche 915. 1987-89 cars may use a Porsche G-50 transmission. The transmission must use Porsche synchronizers.
    2. Differential is free.
    3. Clutch package is free. An unmodified stock flywheel must be used on all transmissions.
    4. Transmission coolers, lubrication, and shift linkage are free.
    5. 915 transmissions must use an 8:31 final drive ratio. G-50 transmissions must use the 9:31 final drive ratio.
    6. The following gear rations are acceptable in any combination:

 915 TransmissionG-50 Transmission
1st Gear11:3512:42
2nd Gear18:33 or 18:3217:35
3rd Gear23:2922:21
4th Gear26:25 or 26:2632:36
5th Gear28:2336:32
  1. Suspension
    1. Stock suspension pivot axis must be maintained by all suspension components.
    2. Front spindle height is free; struts must be O.E. components manufactured by Boge, Bilstein or Koni with the location of the spindle as standard or relocated. The retaining system for the O.E. shock absorber insert must be used. Custom fabricated strut housings are not permitted.
    3. Front and rear shock absorbers must be the same configuration as stock, maximum 2-way adjustment.
    4. Torsion bar suspension required, front and rear. Torsion bar length and receiver locations must be stock.
    5. Suspension bushings are free. Front camber plate/caster plate design is free.
    6. Stock 911 rear control arms only, 930 rear control arms are not allowed.
    7. Adjustable rear spring plates are free.
    8. Anti-roll bar (sway bar) systems are free.
    9. Alignment settings are free, except track width can only be increased from stock by .25 inches per side. Track width must not exceed 65 inces in front and 67 inches in the rear. Measurement is from furthest outside lip of tire on axle center line.
    10. The rear minimum ride height is 215 mm from ground to center of rear torsion bar, with driver in car and the spec tire at 35 PSI.
  1. Tires, Wheels and Brakes
    1. Wheels must be 7x16 front and 8x16 rear. Any aftermarket wheel is allowed.
    2. Tires must be Hoosier R7’s 205 or 225 x 16 fronts and 245 x 16 rears. Hoosier rain tires allowed to correspond o R7’s sizing. Toyo RR or R888 225/50-16 front and 245/45-16 rear may also be used.
    3. Any brake caliper, pad and rotor combination is allowed as long as they fit inside the require wheel size and the roters are steel
    4. Brake lines, air ducting, master cylinder, brake balance control and fluid are free. Dust shields may be removed.
    5. E-brake, parking brake or hand brake system may be removed.
  1. Weight. The minimum weight for this class is 2350 pounds. However, if the car displays a Porsche Racing Club sticker indicating a higher minimum weight, that shall be the weight which must be met.