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2013 Limited X-Modified Rules
CHASSIS
1. Any Engine Part, all frame and suspension components will be steel, unless noted. No titanium or drilled attachment components. 1960 or newer full passenger car frame, may be cut off 36 (inches) in front of center of rear axle.
2. Frames will maintain original dimensions and remain intact except notched for radiator placement, weight jack, spring clearance and mounting tabs. Maximum 2"x4" lower frame may join rear suspension. No portion will be less than 4" from ground except pan and front cross member.
3. 108" wheelbase minimum, with a maximum width of no more than 78" outside tires.
4. Continuous roll cage, halo, and halo support will be of a minimum of 1.501"x .095" steel tubing. Must have one cross bar in halo. This configuration will be attached to main frame in 6 places. Drivers head will be below the halo while seated, three inches recommended.
5. Three door bars will be 1.5" x .095", welded to front and rear uprights, with vertical supports. Must have at least one 1.25" right side cage bar angled or horizontal. Recommend door plates .049" drivers side from top door bar to bottom door bar, Rear post to 5" in front of seat.
6. Rub rail, vertical bar, or rear engine support will be added for foot protection.
7. Must have .250" x 2" plate or 1" x .095" tubing drive shaft hoop, welded 6" behind front of drive shaft.
8. No cage bars will protrude thru hood. Main cage will be behind rear of engine.
9. Will have a minimum of three .250" window bars in front of driver.
10. Two bar front bumpers 1.25x.065 minimum required. Lower bar will be no lower than lowest part of front frame horn and no wider than 1.5 on each side, 6.5 apart and parallel to ground. Upper bar directly above lower bar.
11. Nerf irons will not be wider than outside of rear tires, may not contain any sharp edges.
12. Rear bumpers can be strait, looped or turned forward. Forward turned bumpers can be no wider than 2" outside the rear tires, must be made of continuous hoops. All bumpers must protect fuel cell and line up with front bumpers. Strait bumpers must be no wider than 5" wider than outside rear frame rails. A looped bumper can extend to the body panels.
13. The centers of front and rear bumpers will be 18" high + or - 2".
14. 32 gallon fuel cell maximum with roll over valve. Must be mounted between rear frame rails and behind rear axle. Dimensions of 6" above ground, 4" in front of bumper. Must be mounted securely, in steel box, with 2" straps encircling entire cell. No bottom fuel pickups. One fuel filter maximum. Lower portion of rear bumper will protect full cell. Gasoline only.
15. All ballast will be mounted with two inch diameter bolts, outside driver box, and painted white. All cars will weigh 2300 lbs minimum. Maximum weight will be 2650 after main events, will not be enforced after heat races due to excess mud.
SUSPENSION
16. Unaltered OEM front spindle, lower A-arm, Drag link, inner tie rod ends, steering box, idler arm and pitman arm, sway bar. Steering box must remain in original bolt circle position. No rack and pinion systems. May weld shock mount on lower control arm. Weight jack will be centered in A-arm spring location.
17. May use fabricated upper A-arm with heim joint pivots, steel or aluminum cross shaft. Outer tie rod and tie rod sleeve can be replaced with .625" rod ends and sleeve tubing. May use bump steer spacer on outside of rod ends.
18. Steering and driver position will be on the left side of the driveline.
19. Any steel shock that retails for $140 or less. Coil or leaf spring allowed. Coil springs will be at least 4.5" outer diameter. No torsion bars, air bags, or pressurized springs. One spring and shock absorber per wheel. Four shock absorbers total.
20. No wheelbase or weight jacking devices allowed in driver's compartment.
21. Three link or leaf springs, or factory four link, with two upper arms only. All links will be solid, heim rods. Lower arms will be the same length no shorter than 16". The panhard bar will be a minimum of 19". Must be solid Pull bar with heims, no biscuits or springs.
22. Four wheel brakes at all times. Adjustable from front to rear only.
23. Ford, Chevy, Chrysler parts can be mixed and mounted for use. Brake calipers must be 100% unaltered.
24. No solid, drilled, scalloped, or lightened rotors. May be drilled for mounting purposes only.
ENGINES
25. Engine specifications are as follows:
i. 360 cubic inch displacement or less. Compression of 9.5 or less. 1% error.
ii. Stock type, stamped rocker arms only. No roller tip rocker arms.
iii. Screw-in rocker arm studs are ok. 3/8 studs only with guide plates. No stud girdles of any kind.
iv. Polly locks are okay.
v. Must have cast iron two-barrel intake. No acid dipping, no pressure porting, The depth of the plenum will be measured. Deep side- 3.950" max, Short side- 2.030". We expect to see an unmodified runner to the back of the divider, with ribs that stand up .150". We will use a caliper to measure bores and depth. An unaltered marine cast iron two-barrel intake will be allowed with Vortec heads. You can be disqualified or asked to race with a different manifold.
vi. If intake found to be illegal will loose all prize money for that night and points for that season.
vii. Flat tappet camshafts only. No roller lifters.
viii. Aluminum water pumps & pulleys are allowed.
ix. After-market power steering pumps are allowed.
x. Must have cast iron cylinder heads, original valve angle and location. Valve springs: 1.250 maximum diameter, .195" wire, steel retainers, 5 full coils.
xi. Any Distributor type ignition allowed no crank trigger or magnetos allowed, no timing retard control allowed. All X-Modifieds will be required to use a rev limiter with a 7,000 rpm chip. Chip must be out of reach of driver.
xii. Crankshafts cannot weigh less than 49lbs. Must install a 1" diameter pipe plug to inspect crankshaft, or remove pan.
xiii. No titanium anywhere.
xiv. Tachometer may be claimed for $300 by promoter and lead lap drivers.
CARBURETOR
26. All cars must run an OEM two barrel Rochester carburetor or Holley 4412. The Holley 4412 will require Carburetor adapter Speedway part #135-1934. 1 stock OEM carburetor gasket no more than 1" thick under throttle plates. Throttle bore can be no larger than 1.725" and it must have sharp corner at the bottom of the bores, no modification at this point. May ONLY modify Rochester Carburetor. The Holley cannot be modified.
27. Tracks have the right to swap intake and or carburetor with any competitor after 2nd main event win. Tracks will have stock Chevy and stock Vortec type intake to trade with competitor. Same with Rochester 2 barrel.
DRIVE TRAIN
28. Car must move forward and back with engine running. Will not allow quick change gearing or close ratio transmissions. Bert or Brinn okay.
29. Scatter proof bell housing required on cars with light weight flex plates, single clutch disc and full pressure plates.
30. Any passenger car- or truck-type is allowed. Aluminum is not permitted except lowering blocks, axle cap and drive plate. Quick change devices allowed are not allowed. Nine (9) inch Ford is permitted. Floater recommended. Cambered rear-ends are not allowed (one-piece drive flange only). Traction devices are not allowed (includes Gold Track, True Track or similar type components).
31. All wheels will be 8" wide, measured on the outside of the mounted tire bead. One bead lock allowed on right rear, mud plug allowed any position.
32. The official tire for the USRA Limited X-Mods is the American Racer KK704. Tire can be de-glazed with sanding pads or grinding discs. Re-grooving and siping ok.
33. No electronic engine adjustment devices. No wheel speed engine interface, no traction control. No brake engine electronics.
SAFTEY EQUIPMENT
34. Helmets will be SA 2000 or newer.
35. Drivers will have SFI approved, fireproof: gloves, shoes, and double layer suit.
36. Window net or arm restraints required.
37. A five point seat belt system, properly mounted to cage, Replaced annually.
38. Halo and other interior tubing will be padded.
BODIES
39. .125" aluminum or .060" steel floor recommended.
40. Fully enclosed cockpit, with cowling the same width can not extend past steering wheel.
41. Bodies can be made of steel, aluminum, or fiberglass.
42. Front, rear, and side windows will resemble OEM production.
43. No mirrors allowed.
44. Nose piece can be no wider than front stub and stop at radiator.
45. May run side panels on nose piece. 2" above nose plate and to bottom of front stub.
46. Hood can be no wider that front stub, have a maximum slope of 3".
47. Air filter protector can be no taller than 6".
48. May run engine side panels parallel with frame, from rear of engine to nose piece.
49. Deck will be between 53" to 66" wide, 106" to120" long, parallel with frame, and maximum slope of 6" front to rear. Half way uses up 50% of available slope.
50. Deck can extend 34" to 46" past center of rear axle. Rear of deck will be a maximum of 38" from ground.
51. May slope deck for driver escape. Must be parallel with deck and use 90 degree turns if sloped more than 2".
52. Roof may slope down at the front 5". May be lower at the rear 2" maximum, and be 44" to 52" wide and 41" to 56" long.
53. Roof may be turned down a maximum of for support at the rear.
54. Side window height will be 12" to 18" in height on both sides.
55. Front roof supports can be no longer than 20" and go no farther forward than front of door.
56. Rear roof sail panels must slope gradually to 5" maximum at rear and the same on both sides. May attach to spoiler.
57. 2' wings on front and 5' spoilers on rear will be allowed. (see diagram below)
58. Top of door must be 72" from center of rear axle to motor plate. It can slope forward 8" at the bottom forward portion. The height will be a minimum of 22" tall to 30" max.
59. May use a maximum of 6" plastic at the bottom of doors. Must maintain 3" height above ground.
60. The tire must be visible looking down on the car, but the door can flare out at the bottom.
61. Cars will have a 20" tall and 4" wide numbers on the top and both sides. A number on the right side, rear panel is required.
