HONDA GX 160 - TECH MANUAL
Contents
1. USAC UNITED STATES AUTO CLUB j HONDA GX 160 TECH MANUAL HONDA CLAIM RULE FOR GX160 USAC TYPE ENGINES 13 14 15 Claims will be from within the same division of class only LE x Jr Sr Lt Hvy 120 160 Only competitors in the same division may make a claim on an engine No claiming in Novice class One claim per race event per handler per class Engines may be claimed for 550 00 cash only No claim related inspection will be started prior to the funds being posted with proper official This claim form must be submitted to the Race Director or his or her designee before the end of the race that the claimed engine is participating in LE Checkered flag lap complete The Race Director or his or her designee will hold the claim money until the claimed engine has been inspection for legality The claimed engine will be tagged marked and sealed as soon as it comes across the scale The claimed engine will be immediately taken to impound and or presented to the tech director for inspection Engine must remain in impound and in the possession of tech officials throughout the entire process including shipping to National Tech Director and the transferring of funds Inspection of claimed engine MAY NOT be waived by any party Both claimer and claimee have the option to be present at the time of inspection Any claim that is withdrawn will be assessed a 50 00 fee that will be paid to the host club Multiple claims on an e2. 9 1960 29 1360 49 0730 69 0292 10 1935 30 1285 50 0700 70 0280 11 1910 31 1200 51 0670 71 0260 12 1890 32 1160 52 0635 72 0250 13 1850 33 1130 53 05095 73 0240 14 1820 34 1110 54 0550 74 0225 15 1800 35 1100 55 0520 75 0210 16 1770 36 1065 56 0465 76 0200 17 1730 37 1040 57 0430 71 0180 18 1695 38 1015 58 0420 78 0160 19 1660 39 0995 59 0410 79 0145 20 1610 40 0980 60 0400 80 0135 PLEASE NOTE THAILAND BUILT ENGINES ARE NOT PERMITTED IN USAC COMPETITION
3. The Senior Tech Official reserves the right to allow filters at any event that it s deemed necessary Stock Honda fuel tank must be removed Recoil starter must be removed Pull cup may be cut down for washer Must use original cup Exhaust Stock Honda muffler will be removed Mounting flange may be cut off of muffler and used as adapter flange Any transition from the D shape of the exhaust port to round must take place with in the thickness 0 250 max of the flange This applies to all exhaust systems No steps or tapers allowed grind marks are allowed past 25 flange area No suspension for exhaust flange or pipe infraction just disqualification If an after market flange is used maximum allowable flange thickness will be 0 250 if slip on type flange assembly is used pipe stub will be a maximum 0 880 outside diameter tubing with a maximum overall length of 1 500 Pipe stub must be inserted into exhaust pipe at least 0 750 and will have minimal exhaust leakage Muffler to be used will be 4 to 8 hp Briggs amp Stratton part number 294599 or equal equivalent Muffler will be internally altered except that the round cup shaped baffle may be welded to the perforated baffle without moving it s original location Threads will not be removed from muffler Exhaust pipe will be a maximum of 1 000 outside diameter with a length of 20 0 to 26 0 including a threaded pipe coupler to welded to the end of the pipe in order to
4. parallel to crank 90 degrees from crank Any cylinder block that has one measurement over USAC maximum wear limits will be taken out of service If no measurements exceed USAC maximum wear limits the part of block will not be confiscated Handler has the right to have confiscated parts returned to them but will be rendered unusable B Cylinder bore will not be bored oversize C Cylinder bore will not be re sleeved D Cylinder bore position will not be moved or tipped in any manner E Cylinder block deck will not be resurfaced by any means There will be no polishing sand blasting or glass beading to any interior surface F Deck Height 5 123 minimum 5 127 maximum G Machined surface of block down to thrust face of cam boss 3 220 minimum 3 235 maximum H Machined surface of block down to bearing face 3 416 minimum 3 435 maximum I Oil level sensor will be intact and unaltered Wires may be externally disconnected or cut off PROCEDURE FOR CHECKING TIMING A With degree wheel or indicator located at 0 degrees or TDC mark both the flywheel and some fixed point such as right hand side of aluminum block casting right above flywheel with aligning marks Turn the flywheel clockwise and stop at 26 degrees BTDC or 0 103 0 104 BTDC on your indicator Make another mark on the block casting that aligns with your mark on the flywheel B Remove dial indicator so it will not be damaged by engine rotation C Install
5. screw muffler in place so that muffler may be removed for inspection Pipe coupler will be a standard unaltered 34 NP threaded coupler Length will be 1 000 minimum to 2 250 maximum There will be no steps or tapers in exhaust pipe or flange assembly Exhaust pipe length will be measured by using a small diameter hose inserted though pipe to measure over all length Flange and coupler will be included in the overall length when measuring pipe No coating of any type may be applied to the interior of any part of the exhaust system The intent of this rule is to have all of the exhaust pass through the muffler All measurements are to be taken with the component pieces in the same position as they were installed and on the car 1 All USAC 25 midget mufflers must be Briggs amp Stratton Part 294599 or equivalent No drilling holes in the baffles Inside seam of baffle must be straight edged NOTE Some seams may not be parallel in baffle You cannot cut off the threaded flange if it is to be used in Honda It is Ok to weld a washer or nut on the flange for a place to apply safety wire Choke butterfly amp shaft must be removed Hole may be filled only with silicone Old shaft may be cut down Oil level switch may be disconnected but switch assembly must remain intact in crankcase Gearbox may be rotated to any desired position Main jet in carburetor may be a maximum of 82 0 033 nogo Off On ignition switch may be removed and hole co
6. timing light to a battery if not self powered and clamp inductive pickup to spark plug wire Wire should be hooked to standard spark plug gapped to 0 025 Using a drill with an extension that is cut off or turned to fit drill place socket on flywheel nut and rotate engine in clockwise direction D Fire the timing light and observe If the reference mark on the flywheel is between the two marks on block casting that are TDC and 0 104 or 26 degrees BTDC the timing is legal If mark is not between marks on block casting when rotating the engine will be disqualified Tech officials have the right to tech any or all cars in any class at their discretion Tech officials follow the same chain of command as all officers of USAC as follows Local District National LE District tech officials can tech at any event at their District and National Tech officials can tech at any event in USAC National Tech Director is final authority on all tech issues DECIMAL DQUIVALENTS OF NUMBER SIZE DRILLS No Size in No Size in No Size in No Size in Decimals Decimals Decimals Decimals 1 2280 21 1590 41 0960 61 0390 2 2210 22 1570 42 0935 62 0380 3 2130 23 1540 43 0890 63 0370 4 2090 24 1520 44 0860 64 0360 5 2055 25 1495 45 0820 65 0350 6 2040 26 1470 46 0810 66 0330 7 2010 27 1440 47 0785 67 0320 8 1990 28 1405 48 0760 68 0310
7. type dial indicator Bridge type does not require removing carbon from head surface See photo on next page Combustion chamber cc 17 2 cc Ref with stock spark plug Remove valves Retainer A Inspect retainers for alteration that would increase valve spring pressure Both intake and exhaust must have stock Honda retainers Exhaust valve only can have lash cap and corresponding retainer B Thickness of retainer will be Intake 0 228 minimum Exhaust 0 241 minimum C Flange thickness of retainer will be Intake 0 110 maximum Exhaust 0 070 maximum D From flat of flange to machined surface Intake 0 148 minimum Exhaust 0 165 minimum E All valve oil seals must be removed 1 The use of valve seals is illegal and will result in applicable suspension per Honda suspension program VALVE SPRINGS Valve springs will be stock Honda springs and will not be altered in anyway 160 Spring 140 Spring A Wire diameter 0 071 maximum A Wire diameter 0 079 maximum B Outside diameter of spring 0 790 maximum B Outside diameter of spring 0 808 maximum C Number of total coils 5 3 C Number of total coils 7 D Spring pressure 1 1lbs max at 0 812 D Spring pressure 16 lbs max at 0 812 E Stacked length will be 0 394 maximum E Stacked length will be 0 524 maximum ROCKER ARMS PUSH RODS STUDS Rocker arms will be stock Honda and will not be altered in any way Rocker arm studs will be stock Honda The
8. b Insulator gasket thickness 0 025 maximum B Carburetor identification number BE 65 B C Check carburetor for alterations Upper choke shaft hole may be sealed with silicone type sealer D Carburetor Bore Intake end Maximum diameter 0 951 ref Throttle end maximum diameter 0 710 E Carburetor venture bore 0523 no go This measurement is best made with a no go gauge but may be made using a telescoping gauge as a no go F Main jet and main nozzle MUST BE TIGHT Main jet size maximum 82 0 033 no go Main air jet 0 0587 maximum 53 0 095 no go at back of hole Main jet access passage 0 0942 maximum 41 0 096 no go Main nozzle 1 Main nozzle bore 0 0732 maximum 47 0 078 no go 2 Main nozzle will be checked with a no go gauge 0 424 if gauge goes over dump tube carb is illegal this is best measured using a 0 452 rod type gauge with a 0 424 flat area to be used as a go gauge 3 Air vent holes on the side of the main nozzle must not be plugged 4 Main nozzle must not be fastened into the carburetor body by anything other than the main jet It must not be epoxied or positioned by any other means G Slow Speed system 1 Pilot jet 0 0135 maximum 79 0 0145 no go 2 Pilot air jet 0 0478 maximum 55 0 052 no go 3 Pilot screw no spec 4 Pilot seat diameter 0 0365 maximum 63 0 037 no go 5 Tip of pilot screw 0 020 minimum Float
9. bowl Vent 0 118 maximum 31 0 1200 no go Needle valve seat 0 0685 maximum 31 0 1200 no go The butterfly screw the butterfly and the throttle shaft must not be removed from the carburetor Any evidence of tampering will be a disqualification and suspension Decimal equivalents of numbered size drills chart on page 20 ENGINE COOLING SHROUDS A All pieces of the stock engine cooling shroud must be properly installed B There must be no addition or subtraction of any material from the shrouding except for the covering of the switch hole any material Starter cup may be altered to be used as washer retainer for the fooling fan 1 Remove engine cooling shrouds Remove valve cover 2 Zero dial indicator after exhaust bump 0 050 ref 3 Maximum valve lift will be checked from the top of valve spring retainer Valves may be adjusted to zero clearance or shims may be installed to create zero clearance This may dictate making special shims as it is difficult to insert feeler gauge blades so as not to interfere with indicator contracts on retainer Valve lift Intake 0 245 maximum Exhaust 0 255 maximum CYLINDER HEAD HEAD GASKET VALVES SPRINGS Remove cylinder head Head gasket thickness 0 040 minimum thickness of inner rim Measure from head surface to top of valve head Intake maximum 0 262 minimum 0 242 Exhaust maximum 0 250 minimum 0 225 This is best done with a depth micrometer or a bridge
10. e District Directors Therefore illegal Honda engine parts will be confiscated but the suspension will not be levied against handlers or drivers for the first offense only GENERAL RULES 1 Only stock Honda GX160K1 HX2 and HX26 engine and gearbox will be used in this class All parts will be stock Honda specifically made for the Honda GX1600K1 HX2 U S GCAAK Canada GCABT A All 160 Honda engines must be updated to the new E2 Style piston and cylinder head B Failure to update DQ and minimum 6 month suspension All stock Honda parts must be used and properly installed with the following exceptions A moo OMOZEr AY EAT Governor system may be partially or fully removed with the exception of the steel drive gear on the crankshaft This gear must remain intact If shaft is removed hole must be plugged Hole can be tapped for thread or epoxy No welding Factory air cleaner must be removed Any air filter may be attached to the outside of air filter adapter Outer wear style or equivalent can be used over carburetor only with no adapter The approved air filter adapter may be run with or without an air filter Any air filter may be used with adapter as long as there are no devices inside the air filter or adapter LE Springs not allowed hose from valve cover must go into a catch can WWe are using outerwear to define a style not brand name 1 The use of air filters during qualifying at asphalt and dirt events is illegal
11. ef C Length from bottom of pin bore to top of big end bore will be 2 3755 maximum 2 3580 minimum D Rod weight with bolts 145 grams E No oil grooves on bearing surface of either end CRANKSHAFT Stock Honda crankshaft with no alterations NOTES A No removal or addition of any metal from or to the crankshaft is allowed B No balancing of the crank is allowed C No oil grooving is allowed on the crank journal D Governor drive gear can not be removed E Crankshaft drive gear should not be removed This gear is installed by Honda to any accuracy of degree If this gear is not installed to this degree of accuracy engine may not be legal when camshaft is checked by the procedure under engine block F Keyway location must not be altered in any manner G Measure thrust to crank gear side 3 350 Min H Factory heat treating markings must be present on gear box end of crankshaft and must be evident on all non contact areas The only cleaning method allowed is on the flywheel side of crankshaft for the purpose of removing calcium rust etc from the exposed end of the crankshaft This is permitted only from the seal grove out to the end of the thread of the crankshaft where the flywheel bolts on Only a wire wheel may be used in the cleaning process The use of Scotchbrite sandpaper or any other compounds or abrasives is illegal No material may be added or removed from crankshaft Crankshaft main journal at flywheel and gearbox ends ma
12. heck Bore 2 681 maximum NOTE All measurements taken at top of bore or very bottom of bore Wear Limits Parts Out of Service USAC reserves the right to confiscate 160 Honda engine parts deemed illegal or at USAC maximum wear limits EXAMPLE cylinder bore will be 2 681 max all measurements taken at top of bore or very bottom of bore parallel to crank 90 degrees from crank Any cylinder block that has one measurement over USAC maximum wear limits will be taken out of service If no measurements exceed USAC maximum wear limits the part of block will not be confiscated Handler has the right to have confiscated parts returned to them but will be rendered unusable Check stroke 1 778 maximum to 1 778 maximum to 1 758 minimum Measure amount that piston is up or down from block surface at T D C this will be measured at edge or highest part of piston not in center or relieved area This dimension will be 0 000 Maximum NO PISTON POP UP Install degree wheel on flywheel Install pointer in order to read degrees Locate accurate T D C This should be done with a positive stop type fixture and and not established with indicator alone Cam will be checked with indicator reading off the top end of tappets which will provide zero clearance The inverted radius of the top of the tappet presents some problem to get accurate readings and to prevent binding of indicator stem Indicator holder and pistons are very critical in this operation Zero i
13. m D Thickness of head This will be measured from valve cover surface to head gasket surface at the side at a position in line with upper intake and exhaust flange bolt Maximum 2 917 Minimum 0 911 INTAKE AND EXHAUST PORTS A Ports will be in as cast and factory machined condition and there must be no addition or subtraction of metal or any other substance to the inside or outside of the cylinder head B No alterations of any kind to be made to the intake or exhaust port C This includes any grinding polishing etching sand blasting or glass beading to interior surface E Intake and exhaust ports at valve Intake maximum 0 915 minimum 0 900 Exhaust maximum 0 863 minimum 0 858 ENGINE BLOCK This engine block must be in as cast and factory machined condition There must be no addition or subtraction of metal or any other substance to the inside or outside of the cylinder block crankcase cover crankshaft rod piston pin rings flywheel or coil with the following exceptions A Removal of rear gas tanks brackets is permitted B Removal of governor Governor system may be partially removed with the exception of the steel gear on the crankshaft This gear must remain intact Governor arm and shaft may be removed tied forward or altered to accommodate throttle linkage or return springs C Addition of brackets fittings etc to accommodate throttle linkage tachometer temperature gauge is allowed C
14. maximum is allowed K No plug indexing washers allowed L if temperature sensor is used under spark plug factory washer may be removed GEAR BOX AND RING GEAR A Gear box may not be altered in anyway May be rotated to desired position B Ring gear may not be altered in anyway with the exception of keyed end of shaft that may be shortened drilled and tapped or machined for snap ring grove No other machining drilling grinding etc to ring gear Keyway may be cut deeper C Ring gear may not be altered in anyway including polishing or use of any compound or abrasive on gear shaft where bearings ride CRANKCASE COVER Remove crankcase cover A Cover must be in as cast and factory machined condition and there must be no addition or subtraction of metal or any other substance to crankcase cover B Crankcase cover gasket must be stock Honda Only one gasket may be installed with a maximum thickness of 0 025 Critical dimensions are thrust face of camshaft holder and position of crank bearing Place a straight edge over crank bearing and cam boss thrust face These surfaces should be level Maximum tolerance will be 0 005 There will be no alterations to crankcase cover This excludes any alteration to crank bearing and camshaft holder position and height in an attempt to alter valve timing PISTON WRIST PIN AND PISTON RINGS Remove rod and piston triangle on top of piston must point toward push rods piston wrist pi
15. n and rings must be absolutely stock and not altered in any manner PISTON NOTES Piston will be stock Honda standard size and will not be altered in anyway A Oversized pistons must not be used B All three piston rings must be used and installed properly 1 Top ring Chrome compression ring installed with N on rail up No expander under ring 2 Middle ring Oil scraper ring installed with N or on rail up No expander under ring 3 Bottom ring Three 3 piece oil rings are allowed C Piston may not be knurled grooved or coated D Total Piston weight with rings pin and clips 200 grams minimum E Total piston weight with rings retainers and rod and bolts 360 grams minimum F Minimum total combined weight 360 grams Piston rings complete rod w bolts wrist pins and retainers G See drawing for dimensions RINGS A Must be stock Honda rings with stock size and configuration B No decreasing of ring tension by heating machining or any other means C Ring thickness Compression 0 056 min Scraper 0 056 min Oil ring 3 piece oil ring 0 095 min 1 piece oil ring 0 097 min WRIST PIN Stock Honda wrist pin and retainer OD Minimum 0 708 Maximum 0 709 Length Minimum 2 120 Maximum 2 128 ID 0 556 ref Weight 40 grams minimum CONNECTING ROD Stock Honda rod with no alterations A Connecting rod big end size 1 176 minimum 1 184 maximum B Pin end bore is 710 r
16. ndicator on base circle of cam Be sure that compression release does not affect zeroing exhaust indicator Zero dial indicator after exhaust bump 0 050 ref Turning engine in normal rotation clockwise facing flywheel take reading at specified opening Readings must fall between specified degrees on the following chart IN TAKE EXHAUST Degrees Degrees 0 050 10 5 to 14 ATDC 0 050 207 to 210 5 BTDC 0 100 26 5 to 30 ATDC 0 100 190 to 193 5 BTDC 0 150 45 to 48 5 ATDC 0 150 170 5 to 174 5 BTDC 0 180 Split 0 180 Split 0 200 71 to 74 5 ATDC 0 200 144 to 148 BTDC Maxlift 227 Peak 104 107 ATDC Maxlift 229 Peak 107 5 110 5 BTDC 0 200 136 to 141 ATDC 0 200 70 5 to 73 5 BTDC 0 180 Split 0 180 Split 0 150 162 5 to 167 ATDC 0 150 44 5 to 47 5 BTDC 0 100 180 5 to 185 ATDC 0 100 26 to 29 5 BTDC 0 050 197 5 to 201 ATDC 0 050 9 to 12 5 BTDC Check max lift at intake and exhaust FLYWHEEL FAN AND IGNITION SYSTEM Caution should be used when removing flywheel Do not hit with hammer or other heavy objects Service manual show flywheel to be removed with commercially available 6 puller Another method is inertia type knocker that threads onto crankshaft end The transistorized magneto ignition is fixed at 25 degrees BTDC and may not be altered in anyway Firing must not exceed 0 104 or 26 degrees BTDC Quick check turning flywheel cl
17. ngine will be decided via a lottery system Owner handler or family member cannot claim his or her own engine Claimed party will retain air filter exhaust system and throttle linkage If the claimed engine is found to be illegal the motor must be completely torn down to check for additional illegalities The Tech director must confiscate ALL illegal parts and relate parts from the claimed engine and shall immediately forward them to the National Tech director using confiscation form Claiming party has the option to accept the engine as is less confiscated parts or void the claim if engine is found illegal and claim money will be returned to the person filing the claim Refusal of claim destroying or withholding of parts or any other lack of cooperation in this claim or inspection process will be interpreted as an admission that the engine is illegal and will subject the driver and handler to the conditions set forth in the Honda Suspension Program Any claimed Honda engine part or parts which are deemed to be at maximum wear limits is subject to confiscation but not DQ able The claiming party has the option to void the claim with no financial penalty Note Reference to Wear Limits in Engine Block Internal of both Honda Manuals HONDA SUSPENSION 1 oo Handlers and drivers guilty of having a Honda engine declared illegal at technical inspection shall be disciplined as follows A First offense 30 day suspension for handle
18. ockwise if the leading edge of the depression of flywheel rim where the magnet is mounted is not still under the right hand coil leg at 115 BTDC it is probably illegal and should be checked further If timing needs to be checked further see page 19 A Flywheel keyway or its position must not be altered B Key may not be deleted or altered in any way C Magnet retaining screw may not be altered in any way D Magnet retaining screw may not be altered in anyway Screw may not be replaced with larger or smaller screw No heli coiling of mounting hole E Ignition coil or its position other than air gap may not be altered in anyway Coil mounting bolts must be stock and cannot be altered in anyway to advance or retard timing Coil attaching bolts will be stock 6mm cap screw 1 1 16 long There can be no more than 3 8 of unthreaded portion of bolt that does not measure 0 230 diameter This restricts movement of coil to a position that could make ignition timing illegal If a coil support mount becomes stripped it is permissible to heli coil However only one leg may be repaired if both legs are heli coiled the crankcase becomes illegal F All nylon blades on the cooling fan must be intact G No metal may be added or removed from the flywheel Flywheel weight will be 2390 grams minimum H Flywheel diameter magnet 6 I A stock Honda spark plug cap wire end at resistor must be used J Any automotive type spark plug with 34 reach
19. r Tech Official reserves the right to allow filters at any event that it s deemed necessary B Any type throttle linkage may be utilized Carburetor will be unaltered with the exception of the black plastic piece on upper end of throttle shaft this is the only part in the carburetor that can be altered and 82 maximum jet size C Rear mounting brackets for Honda fuel tank may be removed D The starter cup that is behind the flywheel retaining nut can be cut away to leave only the flat washer back piece that retains cooling fan E The keyed end of the ring gear shaft may be shortened drilled and tapped or machined for snap F Heli coiling threads for shrouds all valve cover existing throttle mounting holes oil drain and fills holes one of the coil bolts and side cover bolts is allowed Dowel holes are not to be modified or relocated also one carburetor mounting bolt G Honing and deglazing of the bore is allowed H Lapping the valves is allowed I Blocking Airflow No device may be used that will or appear that it may impede airflow into the engine cooling system This may require that the engine be run at a speed above idle by the tech personnel at the scale after the car has qualified or raced CARBURETOR Remove Carburetor A Check for any alterations or worn parts that would allow additional air into engine holes slots perforations spacers loose bolts warped flanges etc a Gasket thickness 0 025 maximum
20. r and driver from participating in the respective Honda class B Second offense within one year of first infraction one year suspension for handler and driver from participating in the respective Honda class C Third offense within two years of last infraction suspended for life from USAC Suspension will begin immediately unless there is an appeal at which point the illegal part s will be sent within five days to the District Tech Director or designee for review If the part s are found illegal at this point the suspension will start at that time by the District Tech notifying the person Verified illegal parts will be sent to the National Tech Director legal parts will be returned to person Suspension for life is open to review by the USAC National Board For the purposes of this rule only if a handler has multiple cars competing in the Honda class GX 120 or GX 160 at one race event and more than one engine is found to be illegal at that event it will be considered to be one offense 5 Refusal of tech shall be interpreted as an admission that the engine is illegal and a suspension from the Honda class will be immediate with all awards qualifications being revoked 6 Confiscation of part or parts only the illegal part and all related parts and not the whole motor will be confiscated A full motor tear down is required if an illegal part is found 7 Novice Honda The novice program and its implementation fall under th
21. vered any material no welding All pin measuring gauges are plus tolerance Exhaust oxygen sensor or temp sensor attached to any part of Honda exhaust system is illegal Valve seals are illegal Cryogenics of any Honda part is illegal Note Taking parts out of service reference to Wear Limits in Engine block Internal section DQ only Not suspension for Exhaust Air Filter Adapter Spark Plug Shroud must be factory RED or BLACK TECH PROCEDURE Modifications or machining of any parts in order to bring them to stated minimum or maximum specs blueprinting is no legal 1 External visual check of engine for required components muffler shrouds and sheet metal oil level sensor this can be partially observed from outside NOTES Factory air cleaner must be removed Any air filter may be attached to the outside of air filter adapter Outer wear style or equivalent can be used over carburetor only with no adapter The approved air filter adapter may be run with or without an air filter Any air filter may be used with adapter as long as there are no devices inside the air filter or adapter LE Springs not allowed Hose from valve cover must go into a catch can We are using outerwear to define a style not brand name 1 The use of air filters during qualifying at asphalt and dirt events is illegal The Senior Tech Official reserves the right to allow filters at any event that it s deemed necessary Senio
22. y not be altered in any way Note Refer to photo of crank color CAMSHAFT Camshaft must be stock Honda with no alteration of any kind A There will be no additions to or subtractions from any part of the camshaft B Compression release will remain intact and unaltered C Love center angle will no be altered by any means D Lobe profile will not be altered in anyway CAMSHAFT SPECIFICATIONS INTAKE EXHAUST Heel to Heel 0 865 0 869 Heel to Heel 0 866 0 870 Heel to Peak 1 079 1 93 Heel to Peak 1 081 1 095 Length thrust flange to thrust flange 3 137 minimum 3 142 maximum Cam bearings are 0 547 0 551 and unaltered TAPPETS A Tappets must be stock Honda with no alterations B Base diameter 0 910 no maximum spec C Stem diameter 0 312 minimum D Base thickness 0 076 minimum 0 090 maximum E Length 1 181 minimum 1 220 maximum F Weight 16 grams minimum ENGINE BLOCK INTERNAL The engine block must be in an as cast and factory machined condition and there must be no addition or subtraction of metal or any other substance to the inside or outside of the block A Cylinder bore will be 2 681 maximum 1 Wear Limits Parts Out of Service USAC reserves the right to confiscate 160 honda engine parts deemed illegal or at USAC maximum wear limits EXAMPLE Cylinder bore will be 2 681 Max all measurements taken at top of bore or very bottom of bore
23. y or their mounting position may not be altered in any manner No heli coiling of mounting holes No bending of studs Push rods will be stock Honda and will not be altered in any way Push rod length will be 5 257 5 279 VALVES A Check valves for dimensions and weight Valve seating surface must be factory ground to a single angle only 45 degrees There will be no other angles ground on any part of valve Valves must not be polished lightened or altered in any way B Valve weight Intake 22 grams minimum Exhaust 22 grams minimum C Drawing of valve dimensions Intake valve followed by Exhaust valve HEAD Cylinder head will be in as cast and in factory machined condition and there must be no addition or subtraction of metal or any other substance to the inside or outside of the cylinder head This includes no type of machining or grinding to increase compression or airflow No milling angle milling etc or any alteration that could increase valve spring pressure Note do not use abrasive material in cleaning head and cylinder deck that will alter factory finish A Measure from flat of head surface down to valve seat This dimension will be Maximum 0 305 minimum 0 287 B Measure from surface of head to top of valve guide This dimension will be 1 010 maximum C Measure from surface of head to lowest machined area in the bowl of the port This dimension will be Intake 1 062 1 170 maximum Exhaust 1 103 1 122 maximu
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