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The following related components are recommended when installing GMPerformance Parts Corvette aluminum cylinder head assemblies:
Part Number Description
12555269 Stamped steel rocker cover 10229162 Corvette screw-in oil filler cap 12342056 Chrome screw in oil cap w/GM logo 12338092 Valve cover hold-down bolts (8 required) 14094717 Hold-down bolt washers (8 required) 14088793 Hold-down bolt gaskets (8 required) 14088564 Neoprene rocker cover gasket 12557236 Composition head gasket, .051" thick 12495499 Head Bolt Kit 12495490 Rocker Arm Kit
12363287 — LT4 Design Aluminum Cylinder Head This aluminum LT4 design head is the same as the 1996 production head except it has the LT1 rocker stud P/N 12552126 installed. This head has light weight 2.00" intake and 1.55" exhaust valves installed in this assembly. These heads can only be used on 1992 and later LT1 and LT4 engines. NOTE: This head assembly includes the following items, intake valve P/N 12555331, exhaust valve P/N 12551313, valve spring P/N 12551483, valve cap P/N 10212808, seal P/N 10212810, key P/N 24503856, stud P/N 12552126, and shim P/N 10212809.
P/N	DESC	CSTNG NUMBER	MAT'L	INTAKE RUNNER VOLUME (cc)	COMB CHAMBER VOLUME (cc)	VALVE DIAMETER	SPRK PLUGS	HEAT RISERS	NOTES
12363287	LT4 SERVICE ONLY	NA	ALUM	195	54.4	I: 2.00" E: 1.55"	Angled	No	For LT1 or LT4 usage only
Cam Specs MFG PN DURATION LIFT (1.5) LIFT (1.6) LOBE NOTES LGM N365 211  220 .492  .492 .525  .525 112 1500-6200 LGM N365S 220  220 .492  .492 .525  .525 112 1800-6400 LGM N385 220  230 .480  .480 .512  .512 110 3000-6500 LGM N385S 220  230 .480  .480 .512  .512 112 3000-6500 COMP 08-304-8 210  220 .500  .510 .533  .544 114 COMP 08-206-8 230  244 .510  .540 .544  .576 114 heads, intake, headers, evhaust COMP CCA-215-224-14 215  224 .499  .499 .532  .532 114 2200-5700 COMP CCA-220-230-14 220  230 .510  .510 .544  .544 114 2500-6000 COMP/FIS   215  224 .499  .499 .532  .532 112 custom FIS gind blower COMP extreme CCA-212-218-12 212  218 .488  .495 .521  .528 112 mild COMP extreme CCA-218-224-12 218  224 .495  .503 .528  .537 112 A4 stk converter COMP extreme CCA-224-230-12 224  230 .503  .510 .537  .544 112 1900-5600 gears COMP extreme CCA-230-236-12 230 236 .510  .521 .544  556 112 2200-5800 hvy mods COMP extreme CCA-236-242-12 236  242 .521  .540 .556  .576 112 2500-6000 COMP extreme CCA-204-218-14 206  218 .480  .495 .512  .528 114 Blower Nitrous COMP extreme CCA-212-224-14 212  224 .485  .503 .519  .537 114 Blower Nitrous COMP extreme CCA-218-230-14 218  230 .495  .510 .528  .544 114 Blower Nitrous COMP extreme CCA-224-236-14 224  236 .503  .521 .537  .556 114 Blower Nitrous TPIS 700-134 212  236 .483  .520 .515  .555 112 ZZ9 for 93-96 TPIS 700-142 212  226 .483  .520 .515  .555 112 ZZ9 for 95-97 GM   .450  .450 .480  .460 93 LT1 STOCK GM 230  208 .450  .460 .480  .491 116 94-95 LT1 STOCK GM 205  207 .447  .459 .477  .490 117 96 LT1 STOCK GM 203  210 .446  .449 .476  .479 115 96 LT4 (STOCK GMPP 10185071 208  221 .474  .510 .506  .544 112 ZZ3 GMPP 24502586 218  226 .492  .492 .525  .525 112 LT4 HOT GMPP (Crane) 12370845 214  224 .488  .509 .521  .543 112 GMPP (Crane) 12370846 222  230 .509  .528 .543  .563 112 GMPP (Crane) 12370847 232  242 .539  .558 .575  .595 112 GMPP (Crane) 12370847 232  242 .539  .558 .575  .595 112 Crane 19HR0064 198  206 .480  .480 .512  .512 112 Crane 104124 214  220 .452  .465 .481  .496 112 2000-5500 Crane 104121 204  214 .429  .452 .458  .482 116 Crane 104125 208  214 .438  .452 .467  .482 112 Crane 109621 214  222 .489  .509 .520  .542 112 Crane 104141 218  218 .498  .498 .531  .531 116 Crane 10HR00013 214  222 .488  .509 .520  .543 112 Crane 10HR00017 214  218 .488  .498 .520  .531 114   Crane FIS 215  224 .499 .499 .532  .532 112 Custom blower grind Crower LM-00402 219  227 .498  .518 .531  .553 108 DRM 222  230 .508  .528 .542  .563 108 Lingenfelter 74211 211  219 .499  .525 .530  .560 112 1600-5200 Lingenfelter 74216 213  219 .462  .471 .493  .502 112 1600-5200 Lingenfelter 74219 219  219 .525  .525 .560  .560 112 1600-6200 Lunati 50160 312-218 .446  .468 .475  .499 110 1500-5300 Lunati 50155 215  218 .489  .503 .522  .537 113 1500-5500 Lunati 50156 232  242 .510  525 .544  .560 108 2000-6500 Lunati 50162 242  252 .525  .540 .560  .576 108 2200-6800 MTI 210  220 .500  .510 .533  .544 114 MTI 230  244 .510  .540 .544 .576 112 General  Information for Cam Selection DURATION: Duration is the time the valve is open, and is measured in crankshaft degrees. The duration can (and usually is) different between the intake and the exhaust, with the exhaust being open longer (more duration). More duration will move your powerband up. For instead, a 195 dgr duration cam may have a power peak at 4500 rpm, where a 250 dgr cam may have a power peak of 6500 rpm (number grabbed out of the air, but should give a sense of the numbers). Look for duration measured at 0.050 lift. That will give you a truer idea of the cam. There's also 'advertised duration', recognized by the very large numbers. You should concentrate on the dur@050 numbers. When a cam is said to be a '205 dgr cam' it usually means 205 degrees @ 050 intake duration. Exhaust may be more duration. This is because the intake duration is more critical for how the motor will run than the exhaust duration. Stock for the LT1 is in the 201-205 range intake (different for different years). A stock car has a power peak at 5000rpm. But other breathing mods such as porting the heads can move the peak up even though the cam remains unchanged.Increasing duration usually increases peak hp, but decreases low end torque. It also increases overlap (see the overlap section below). LIFT: The maximum amount (in inches) the valves open. May (and often is) different between intake and exhaust. Lift is generally a Good Thing. More lift makes more torque and horsepower. What limits valvelift is physical contact between valves and pistons or contact between retainer and valveguide. With non-roller camshafts (all LT1s have roller cams), high lift was difficult. this is less of an issue with our roller cams. When increasing valvelift, the valvesprings have to be checked to make sure they can take the additional lift without binding. Stock lift is around 0.459" on the exhaust valve. Stock LT1 springs get marginal around 0.490". Most aftermarket cams will put you in the 0.520-0.535 range, and you have to get better springs. Only drawback to lift is that it tends to make a torque curve peaky, i.e. increase midrange while hurting upper and low rpm. This doesn't seem to be too much of a problem on the LT1, though. Even with very high valvelifts, the torque curve stays remarkably flat. LOBE SEPARATION Lobe separation is the number of degrees the intake and exhaust lobes are separated. More separation decreases overlap (see overlap below). However, tighter lobe separation makes more high-end hp. LOBE CENTERLINE: The relation between the camshaft and the crankshaft. Nearly all street cams like to be 4 degrees advanced. OVERLAP: This is the killer for street engines. Overlap is the amount of degrees that the intake and exhaust valves are open at the same time. Unburned air/fuel mixture will be pushed through the cylinder when both valves are open and straight out the exhaust. This decreases mileage, increases emissions, and make the engine run rough at low rpms. It also decreases low-rpm torque, and hurts throttle response. All cams have some amount of overlap. Stock cams all try to keep the overlap low for the above reasons. More duration with no other changes will increase overlap. One way of lowering overlap after it's been increased by more duration is to increase lobe separation. This is because moving the lobes away from each other decreases the time they are open simultaneously. CAMSHAFT CHARACTERISTICS RANGE SELECTION RANGE 1 CAMS UP TO 195° DURATION @ .050" RANGE 2 CAMS FROM 195° - 214° DURATION @ .050" RANGE 3 CAMS UP TO 215° - 224° DURATION @ .050" RANGE 4 CAMS FROM 225° - 240° DURATION @ .050" RANGE 5 CAMS FROM 241° -272° DURATION @ .050" Idle Quality Stock idle quality. 18-20" of fld. vacuum. Smooth idle quality. 16-18" of fld. vacuum Fair idle with slight lope. Low Mfld. vacuum, may require vacuum reserve tank. Choppy idle characteristics Low Mfld. vacuum. Will not operate power brakes. Very rough idle. Low Mfld. vacuum. Will not operate power brakes. Power Band Most efficient from idle to 3,000 rpm Best power band from 1,500 to 4,000 rpm Excellent mid range throttle from 2,500 to 4,000 rpm. Excellent top end power from 2,200 to 6,500 rpm. Best power band from 3,200 to 7,500 rpm. Torque Band Excellent low to mid range torque from 1,000 to 2,500 rpm Excellent low to mid range torque from 1,500 to 3,500 rpm Excellent mid to top end torque from 2,500 to 4,000 rpm Excellent top end torque from 2,500 to 6,000 rpm Excellent low to mid range torque from 3,500 to 7,000 rpm Various parts required when swapping the cam in a 4th Gen F-Car Part desc MFG PN Qty Water pump gaskets    GM 10128343 2 Intake valve stem seals     8 Exhaust valve stem seals     8 Intake manifold gaskets  Felpro MS95580 set of 2   Felpro FEL-1284 set                                            GM 12524653 set of 2 Front cover gasket            GM 10128293 1 Front cover seals (water pump drive) GM     Front cover seals (Opti drive) GM     Front cover seals (Crank hub) GM     Head Gaskets        (Impala SS) .____ thk GM 12553160 set of 2                                             (LT1) .____ thk GM                                                 (LT4) .____ thk GM                                      93-97 (LT1) .039    thk Felpro FEL-1074 2                                  93-97 (LT1) .046    thk    Mr. Gasket Ulta Seal MRG 5715 2                                  93-97 (LT1) .026    thk    Mr. Gasket Ulta Seal MRG 5716 2                 Valve cover gasket       (stock stamped valve covers)    GM 10046089 2                                          LT4   composite valve cover GM 10108625 2 LT4 Hot Cam Kit (cam, rockers, springs & retainers) GM 1248002   Crane valve springs (stock dia. - up to .60 lift)   99846-16 set of 16                above uses stock retainers, lock & seats       Crane valve spring (larger dia. w/retainers, lock & seats   10308-1 set         LT4 timming set       Chain GM 12555887 1 Gear 1 GM 12555885 1 Gear 2 GM 12555886 1 LT4 Extreme timming set GMPP 12370835 1          (incompatable with 93-94 optispark)       LT4 Extreme timming set Cloyes 9-3151 1 95-97 Optispark GM 1104032 1         LT1 hyd. roller lifters   COMP CAMS factory replacement COMP 850-16 set of 16                          "R" Series Hi-rev  COMP CAMS COMP 875-16 set of 16         While your in there, how about replacing the push rods?       Stock lenght: 7.200 TRICK FLOW TFS-21407200