|
Rules For Super Box Class
SUPER BOX 6.5 OHV, HEAVY – Age 15 years & up – 375 lbs. Only 87-93 octane gasoline. Approved Engine: Box Stock Project 6.5 OHV modified only according to AKRA Super Box 6.5 OHV Engine Spec. Stamped steel drum, shoe-type clutches only with any gear. Maxxis tires only, any compound.
ENGINE SPECIFIC TECH SHEET FOR: Super Box 6.5 OHV
Description: Single cylinder, 2-valve overhead 4-cycle engine. No aftermarket coatings of any type are permitted on any part of the engine.
Cylinder Head Requirements: Stock (Box Stock Project) cylinder head only. Machining of gasket surface allowed. Porting allowed, but seats must remain stock and cannot be touched in the porting process; no pin punching or rifling allowed, and no addition of material in ports or to cylinder head allowed. Valve seats are two angles, 45° valve face and 30° top relief. Stock Head Bolts are required and all four are required. Minimum head gasket thickness is .009”. Must use stock head gasket, but more than one gasket may be used. Cylinder head guide plate for pushrods must remain stock.
Bore and Stroke: Stock bore is 2.768” and may be over bored to 2.718” (approximately .040” overbore). Stroke is 2.123” +/-.005”.
Combustion Chamber Volume: 25 cubic centimeter minimum with piston at TDC using prescribed procedure and tech plug.
Carburetor Requirements: Stock Appearing (Box Stock Project) Huayi carb with a .625” maximum venture diameter. Air Filter adapter of 1.375” max length allowed. Floor pan mounted fuel tank required (stock tank to be removed) and pulse-type fuel pump allowed. Fuel pump must be pulsed from either the crankcase or the valve cover. Black phenolic carb insulator must be used. Choke assembly may be removed. Jets, tubes and orifices are non-tech.
Valve Train: Rockers, ball adjusters, rocker arm studs, lock nuts, pushrods, and lifters must be stock as from factory. No additional support for rocker studs permitted. Stock valves only. Valves must be one angle only, 45°. No polishing or lightening of valves. Any single valve springs allowed. Any aluminum or steel valve spring retainers are allowed. Any steel retainer locks and lash caps may be used.
Camshaft Requirements: Max lift of .275” taken with zero valve lash directly off valve retainer.
Ignition system: Box Stock Project ignition module only. No modifications of any type allowed. Sparkplug connector must be stock as from factory.
Piston Requirements: Must be stock dished piston with no modifications. Oversized Honda OEM dished (ZLO) pistons of Box Stock Project piston’s appearance may be used. Piston CAN NOT ALLOW FOR ANY POP OUT!
Connecting Rod: Billet aluminum rods, with or without bearing inserts allowed. No titanium rods allowed. Rod length is a non tech item.
Crankshaft Requirements: Stock, factory crankshaft only with stock, factory timing gear in factory location. Timing gear may be tack-welded to crankshaft in 2 places to avoid slippage. No modifications to crankshaft allowed. Aftermarket main bearings of non self-aligning type, with or without seal, allowed. No ceramic bearings. Crankshaft Journal diameter is 1.180”, 1.175” minimum.
Block Requirements: Stock Block, as cast and produced with no alterations or modifications other than those specifically permitted. Block head matting surface may be machined, however, no piston pop out is allowed. Blocks may be welded for repairs as long as the repair does not constitute a functional modification to the block. No welding to block from cooling fins upward to deck surface. Governor stub hole may be tapped and plugged. All bolt bosses in block may be drilled and tapped for repairs or other uses. Additional side cover gaskets as required for crankshaft thrust are permitted.
Flywheel: SFI certified ARC model 6619 or model 6618 billet flywheel with cooling fins only with no machining or alteration of any kind allowed. Minimum weight for flywheel is 3.3 lbs. Any timing key or no key at all may be used. A flat washer may be used, and is recommended, between the flywheel and the nut.
Header and Muffler Requirements: Any single stage, one-piece header made from 1.0625” O.D. steel tubing. I.D. of tubing is .920”-.930”. A maximum 2.5” long swedged flange is required at the end of the pipe for muffler mounting. Maximum outside longest length of the header, including flanged portion for muffler is 22”. Header may be bent in any configuration to keep it away from the driver and so the muffler will not extend past the rear bumper. The RLV 8-91 muffler/silencer is mandatory and may not be modified in any way. Header must be securely wrapped from flange to swedge prior to the race.
|
