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Northwest Pro4 Truck Series
Construction Rules Section 2016-2017
The purpose of these rules is to provide a standard of racing for an economy class of compact truck for the enjoyment of racing. If you cannot abide by this set of rules, do not build a truck to run with this class. If you do not see it in this rulebook, do not do it without contacting the race director.
1. Approved Trucks: Any compact truck, e.g. Chevy S-10, GMC S-15, Ford Ranger, Ford Courier, Dodge D-50, Datsun, Nissan, Toyota, Mitsubishi, Chevy Luv, Mazda B- Series, Isuzu, etc. Foreign or American two-wheel drive only. No 4-wheel or front wheel drive trucks. Any other trucks must be approved. Extended cabs or extra cabs allowed. Extended and extra cab trucks must meet rear firewall rules (no cage or seat setback). If you are planning on building a truck, call the race director to make sure it is a legal chassis.
3. Engine Setback: Engine setback is not to exceed the number one spark plug with the upper ball joint.
4. Engines: Four Cylinder inline single camshaft motors. No roller cams. Any engine in any truck. Maximum 2600CC. No rotary engines allowed. Factory 2600cc engines will be given allowance for refreshening up to 0.060” over stock bore.
5. Block: Block must be mass-produced by OEM. Block must use OEM Crankshaft FOR BLOCK USED. No Aftermarket crankshafts of any kind allowed. Rods must be steel. No aluminum, titanium, or other exotic rods allowed. Flat top pistons only.
6. Cylinder Head: Must be mass-produced by OEM. Heads may be milled. Any deburring, porting, or polishing of cylinder head will add 100 lbs. to truck. Hydraulic, heads with untouched ports will be allowed to remove 100 lbs. No SVO heads.
7. Intake: Any aftermarket or stock intake manifold for motor used. No homemade intakes. Stock intakes may be machined. No more than 3 inches between the plenum and carb. A 1/4 inch allowance for gaskets. O.K. to rotate carb. Welding of alftermarket intake allowed to turn carb.
8. Carburetor: Any two barrel carburetor can be used. Choke mechanism and choke horn may be removed. Air cleaners are mandatory. No sidedrafts, blowers, injectors, or turbos allowed.
9. Transmission: Any stock transmission with three, four, or five, speeds can be used. Automatic transmissions must use a torque converter. No in/out boxes.
10. Flywheel and Clutch: Must use a disk clutch and pressure plate. No ram style couplers, no direct boxes.
11. Scatter Shield: Scatter shield mandatory. Must cover clutch and flywheel. Minimum 3/8” belt material.
12. Driveline: Drivelines are to be painted white. Drivelines must have a metal strap twelve inches maximum behind front universal joint.
:: 2150 lbs. with hydraulic head (tappets) ports must remain untouched in stock condition. No deburring, porting, or polishing.
:: 2250 lbs. with solid head (tappets) ports must remain untouched in stock condition. No deburring, porting, or polishing.
:: 2350 lbs. with ported and/or polished heads. Hydraulic or solid head.
:: 2350 lbs. - Roller Cams Un-ported Roller cams allowed - Ports must remain untouched in stock condition, (no deburring, porting or polishing).
:: NOTE: All added weights MUST BE PAINTED WHITE
14. Roll Cage: Full roll cage made with minimum 1.5” Steel Tubing .095” wall thickness. Door bars must be installed (three on the drivers side and two on the passenger side) The main cage will be of standard roll bar tubing. NO SQUARE, GALVANIZED, WATER, GAS, ECT. TUBING ALLOWED. Right side of cage will not be left of inside frame rail. The cage must have a minimum of 20ga. steel on the outside of drivers side door bars from A pillar to B pillar. Must have center bar in halo.
15. Firewall and Floor pan: Firewall and floor pan will be fabricated of 20 ga. or thicker steel. All holes will be filled. Entire area surrounding driver to be steel (no aluminum) from front to rear firewalls. Rear firewall may be of aluminum construction. Floor pan to be above top of frame rail at all points. You may not cut or alter frame in any way for floor pan clearance. If using any or all of the stock firewall and floor pan new steel must be welded (no rivets) and approved by Tech and rules committee. Rear Firewall to be no more than 75 inches from center of upper ball joints. 75 inches applies to extended cabs as well. Front firewall to be no more than 18 inches from center of upper ball joints. Drivers must be fully separated from outside and underneath of truck by interior panels. Crush Panels may be of aluminum construction. Cab of truck must be centered on frame rails.
16. Fuel Cells: Mandatory. Must be securely fastened in bed of truck between frame rails. Must be enclosed in a 22ga. steel box with top. Must be at least 12 inches in front of rear bumper, with hoop. Subject to tech approval. All trucks equipped with electric fuel pumps are required to have an oil pressure activated cut off switch. Momentary bypass switch is allowed.
17. Battery: Must be securely fastened in bed of truck. Clearly labeled (ON/OFF) and accessible master switch required on top of bed behind driver. Another kill switch will be inside of cab within reach of the driver while belted in.
18. Minimum Ride Height: Frame ride height is a minimum of 4 inches without driver. A 1/4 inch tolerance post race.
19. Suspension Front: Stock unmodified OEM lower control arms of frame used, mounted in the stock location. May use aftermarket bushings. May use aftermarket upper control arms, with mounting optional. Any OEM spindle allowed. No aftermarket drop spindles. IMCA stock spec Pinto spindles allowed. Weight jacks allowed. Front frame may be cut up to 6inches back for bumper mounting purposes only. Stock type rack and pinion allowed.
20. Suspension Rear: Front mount on rear springs to remain in stock location and parallel to frame. Pan hard rod or Watts linkage allowed but must be parallel to axle. No torque or traction devices of any kind allowed. Must use suspension for year and make of truck.
21. Rear Ends: Any rear end allowed. Welding of gears and spooling are permitted. If the rear end is changed it must be remounted with stock components of truck used. No traction devices of any kind. No limited slips.
22. Wheel base: Minimum wheel base will be 101 inches.
23. Springs: (1 spring per corner)
:: Front: You may cut or heat. Aftermarket Springs allowed.
:: Rear: No fiberglass leaf springs allowed. Aftermarket leaf springs allowed.
24. Shocks: Any steel body, adjustable steel body, or rebuildable steel body shock allowed. No aluminum body, coil over, or canister style shocks allowed.
25. Sway bar: Any 1 piece sway bar may be used. Mounting optional.
26. Brakes:Trucks must have all four-wheel brakes in working order. Only stock parts allowed on front spindles. May use aftermarket master cylinder, pedal assembly, and brake bias valves. Aftermarket rear disc brakes are O.K.
27. Exhaust and Muffler: Header may be used. Exhaust to exit behind cab of truck.
28. Radiator: Will remain in the front of the engine and have an overflow can, 1 qt. minimum. No antifreeze, no glycol based products.
29. Fire Suit: All drivers must wear a track approved fire suit, shoes and gloves. Fire suits will be worn at all times while in the truck and on the race track.
30. Helmets: All drivers must wear a track approved Helmet. Helmet will be worn at all times while in the truck and on the race track. Snell SA-2005 minimum
31. Fire Extinguisher: Securely mounted within drivers reach, 2 lb. minimum. Fire control system highly recommended. Every driver must also have a fully charged 10 lb. Class B fire extinguisher in their pits at all times.
32. Seat: Metal seat and headrest required. Must meet racing specs. Joe’s, Butler built, Kirkey, etc. Mounted by Manufacture’s specifications. No home made, fiberglass, or plastic seats. Seats must be mounted to roll cage. Subject to Tech. Approved carbon fiber style seats allowed. (Call race director first)
33. Belts: Three inch lap and shoulder harness. 5 point recommended. Other belt sizes to accommodate Head and neck restraints should be to Manufacturer’s specifications. All belt’s to be mounted to Manufacturer’s specifications. Belts to be mounted to roll cage. No running shoulder belts up the back of seat. Must not be more than 5 years old.
34. Window Net: Window nets are mandatory. Must cover tightly from B pillar to steering wheel with one easy connection at top left. Connection must be clearly marked for easy removal by track officials, and of sturdy construction.Minimum 3/4 inch belt material.
35. Tires: Hoosier and Goodyear Short Track Special (A300 compound) only.. Both tires allowed for the duration of the 2016 season, however, due to the growing age of the Goodyear tires they must be presented to tech for inspection prior to use at every race where their use is intended. Tech reserves the right to reject any tire they feel is unsafe
35a. Tires will be marked prior to qualifying: you must run the same tires you qualify on, in any points event for that evening. If you need to change a tire for any reason, after qualifying you must have tech approval.
36. Wheels: Approved racing wheels of 8 inches maximum width. No aluminum wheels.
37. Fuel: Pump gas, Aviation fuel, and Racing fuel are allowed. No exotic fuels allowed such as alcohol, nitro-methane, etc.
38. Radios: Allowed. No driver to driver communication during any points event.
Copyright© 2013 Northwest Pro4 Trucks Series and Woodpecker Graphics