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Chevy Small-Block V8  |  Cylinder Heads
 

 
 
 
Quick Reference Charts

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10033867 Pontiac Motorsports Head      
This aluminum head for small-block V8s offers a substantial increase in both airflow and horsepower with minimal preparation. It has a standard intake port location, and is compatible with most small-block V8 components. Ductile iron seats for standard length 2.100" intake valves and 1.625" exhausts are installed. Phosphorous bronze guides are included with this head but are not installed. It has conventional 62cc combustion chambers, and uses 3/4" reach gasketed 14mm spark plugs.   Small Image
Technical Notes: For gaskets and component refer to Chevrolet V8 section.

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10051101 Raised Runner Aluminum Bow Tie Head      
The intake runners in this Bow Tie cylinder head (casting P/N 10051101) are .200" higher than the small-block Chevy's stock port location. These raised runners enhance engine airflow and increase horsepower. The .240" minimum wall thickness allows extensive port modifications. The rocker cover rails are raised .300" and the intake manifold flange is stepped to improve gasket sealing. The raised runner head's 55cc combustion chambers enhance combustion efficiency and suppress detonation. These small chambers yield high compression ratios even with small piston domes. The spark plug holes are machined for 3/4" reach plugs with gasketed or tapered seats. The minimum deck thickness is .600-inch.   Small Image
Technical Notes: The raised runner head is sold without valve guides and seats. The raised port design requires aftermarket valves which are .100" longer than stock. Production valves can be used by remachining spring pockets. Pushrod clearance holes are deleted to allow widening of the intake ports. Pushrod guideplates P/N 14011051 are required with raised runner heads. Raised runner intake manifold P/N 10051103 is recommended for all single four-barrel applications.

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10125377 Cylinder Head Assembly      
This is a cast iron cylinder head assembly used on 285 hp 350 engine (P/N 12353641). This complete cylinder head assembly includes 1.94" intake valves, 1.50" exhaust valves, valve springs (P/N 3901068) and valve spring caps (P/N 14003978).   Small Image
Technical Notes: This cylinder head has 64cc chambers. The cast number for this head is P/N 14101083 or 14096217. This cylinder head has 1987 and later inlet manifold bolt pattern. The center two bolts are at a 72º angle.

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10134364 18º Cylinder Head, High Port Small-Block V8      
This cylinder head for competition small-block V8's represents a significant performance improvement over the Phase 6 head. The design moves the valve angle to 18º from its previous 23º. The valve centerlines are relocated .275" toward the intake manifold which positions the intake and exhaust valves on the centerline of the cylinder bore. This minimizes shrouding at high lift and also allows for the installation of larger valves (up to 2.20"). The valve centerlines are also shifted laterally to provide proper valve clearance with a variety of cylinder bore and valve head diameters. The intake runners are now raised, and floors of the intake ports are 1.220" above the deck surface. At valve lifts above .600", this configuration produces superior airflow. Shallow, wedge-shaped combustion chambers achieve high compression ratios with small piston domes. Spark plugs are closer to the center of the cylinder bore and shifted toward the top of the chamber, which improves flame across the chamber and reduces spark advance requirements. Exhaust flow is also increased because ports are .450" higher and .240" wider at the exhaust manifold flange than the Phase 6 Bow Tie head. The low-port configuration satisfies sanctioning body rules that require conventional port location, and are recommended for carbureted applications with limited hood clearance.   Small Image
Technical Notes: Does not include valve seats or guides.

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10159552 Cylinder Head "Bare"      
This cylinder head is a service head less valves and springs which is used on the 350 ci (300 hp) engine. This head is an excellent replacement for street use. It has 1.94" intake valves, 1.50" exhaust valves with 64cc chambers. They require late model center hold down valve covers.   Small Image
Technical Notes: This cylinder head has 64cc chambers. The cast number for this head is P/N 14011083 or P/N 14096217. This head has the standard 1955-86 angle manifold attachment holes.

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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.   Small Image
Technical Notes: 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.

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12370855 Cylinder Head, X-Ray 18º for 9.1:1 CR      
This 18º V8 head is the same as P/N 24502580 except it is x-ray inspected to insure quality, then hot isostactic pressed (hipped) to remove porosity, and it then receives special low volume heat treatment. This head was designed for 9.1 NASCAR engines.   Small Image
 

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12464298 Cylinder Head "Aluminum Fast Burn"      
This head can be used on any 1958-99 283-400ci small block Chevrolet V8 engine with conventional water flow design, but this head cannot be used on any LT1, LT4, or LS1 engines that are designed with reverse water flow. The all new 23? Fast Burn small block cylinder head has the highest performance potential of any 23? small block head developed by GM. The Fast Burn head combines new technologies with the best of GM motorsports and production cylinder head technologies. The design creates tremendous power on engines from 350 to over 400ci. The name "Fast Burn" refers to the head's ability to quickly and completely burn the air fuel mixture, resulting in higher cylinder pressures and more power. The shape of the combustion chamber is designed to accomplish this "Fast Burn" with flat top pistons, so flat top pistons are recommended with this cylinder head. It is not recommended that the combustion chamber be modified or reshaped, as this could decrease the efficiency of the chamber. This head is designed with a .400" deck. This new technology removes material from other portions of the head, allowing for considerably larger ports and water jacketing. The deck also provides unsurpassed clamping force for cylinder head gasket retention. The super rigid .400" deck thickness can be machined down to .340" safely for all-out performance applications and higher compression. Other ways to adjust compression ratio with the Fast Burn head include top of piston design and piston installed height. Unlike the GM Performance Parts Bow Tie heads and most aftermarket performance heads, this head requires no additional porting for maximum performance. In the past, the industry has added material to heads to allow substantial porting, which can result in poor "out-of-box" performance and additional cost. The Fast Burn head utilizes GM Performance Parts' Cast-Ported technology, which means that improvements in flow, combustion and cylinder fill were incorporated into the machining tooling, achieving maximum performance "out-of-box". While additional porting is not recommended, light sanding to remove minor casting imperfections and polishing of combustion chambers and exhaust ports is acceptable. All Fast Burn heads are CNC machined to exacting tolerances, thus eliminating the need for "blue-printing" of machined tolerances, resulting in a cost savings and unsurpassed "out-of-box" performance. This head has taller than typical rocker cover rails, providing exceptional clearance for rocker arms and valve train supports typically used in all out performance applications. The rocker rails are CNC machined for superior rocker cover gasket sealing. Front head faces are drilled and tapped for typical accessory drive bracketry. The Fast Burn head accepts both center bolt and early style four bolt flange mount valve covers. Signature etched with GM Performance Parts logo. Intake manifold mating surfaces are drilled and tapped for both Vortec and conventional raised port style manifolds. "D" shaped 78cc exhaust port and runners provide adequate flow for applications well in excess of 500 hp. Raised runner (.240" higher than conventional 23? head) intake ports with 210cc ports and runners provide adequate flow for applications well in excess of 500 hp. Raising the top of the intake valves provides a better "line-of-sight" through the port and onto the back side of the intake valves. The 62cc fast burn combustion chambers - the most efficient ever to be incorporated on a GM Performance Parts cylinder head - produce higher cylinder pressures by burning more of the available fuel before the piston starts its power stroke downward. By more completely using available fuel, the engine produces more power per quantity of fuel. The 2.00" hollow stem lightweight intake valves are utilized to reduce loads on valve train systems at high rpm's. The 1.55" sodium filled lightweight exhaust valves have all the same benefits of the hollow stem intake valves, and additionally they are able to perform under extremely high-temperature performance applications. This head has specially designed "deep" valve seats which can accommodate up to 2.02" intake valves / 1.600" exhaust valves. Lightweight valve spring retainers combine with the lightweight valves to help ensure long-term high rpm durability. Screw-in 3/8" rocker studs are used, and accept most available roller rocker arms. Uses all conventional "low cost" readily available 23? rocker arms and valve train supports and hardware. This head is a bolt-on 30 hp increase when used on our ZZ4 crate engine. When tested on a 383 ci small block engine with 9.5 to 1 compression ratio and .540" lift roller cam, single plane intake manifold and 750 cfm Holley carburetor, the Fast Burn heads produced 497 hp at an incredibly low 5800 rpm. Total ignition timing to be used on a Fast Burn head will vary based on a number of factors, but most configurations made the most power with 34 to 36? of total timing.   Small Image
Technical Notes: Use intake manifold P/N 12496820, P/N 12366573, 12496822, or 10051103 with the Fast Burn cylinder head. Use intake manifold gasket P/N 12529094 and eight attaching bolts P/N 12550027. Use Fel-Pro exhaust gasket P/N 1470 for these Fast Burn heads (some trimming may be required for your application. This head includes intake valves P/N 12555331, exhaust valves P/N 12551313, valve spring cap P/N 10212808, and valve springs P/N 12551483.

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12480005 Cylinder Head, "Gen 3" V8 (LS1)      
The "Gen 3" V8 (RPO-LS1) engine is used in all 1997 and later Corvettes, and 1998 and later Camaros. A special manifold must be fabricated to use this head. Use with special cylinder block P/N 12480030. To compete successfully in GT-2 racing an aftermarket parts development started with the intent of providing the new GM powertrain LS1 engine a higher performance platform. The first component designed was the cylinder head with an intent to provide a part that was similar to the LS1 in appearance for sanctioning body approval. The cylinder heads include the following features: The basic height, width and attachment faces are in stock location to dowel and deck position. All dimentions and fasteners are metric. The basic valve angle was revised from 15 to 11 degrees to produce a smaller chamber. The valve angle also provides more space for aftermarket rocker arms. Jesel valve train systems has provided the current race pieces. The production individual pedistles are cast into a continuous feature tieing all the bosses together. The rocker cover hold down bosses are incorporated into the rocker arm plateau for the 4-bolt center hold down type cover (1999 model year). The chamber volume for the P/N 12480005 head is 38cc with flat faced valves of .75mm inlet and 1.5mm exhaust margins. The P/N 12480090 provides additional material for CNC porting and chamber shaping and starts at a volume of less than 30cc's. The inlet port roof and floor is raised and the attachment pattern is designed for a Kinsler fuel injection manifold. Inlet port is 57.15 x 36.58mm / 55.957mm dia. precision finished. The cylinder head is machined for larger diameter springs (41.5mm or 1.63" dia. machined pocket). The exhaust flange is identical with the production part. The exhaust port is stock size. The head is machined for a 12.712 / 12.688mm dia. valve guide bore. Rocker cover oil rail seal is a reverse tapered groove for a 3.2mm dia. (.125") free length "O" Ring.   Small Image
 

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12480011 SB2.2 Aluminum Cylinder Head      
This aluminum cylinder head, designed for Winston Cup competition style racing, is very similar to the SB2 head P/N24502559 released in 1996. This head was designed to improve durability, simplify preparation procedures, and reduce the overall cost of building and maintaining a small block racing engine. Intake ports are a "mirror" design; exhaust ports remain the same as original SB2. All eight ports are angled toward the center of the engine. The SB2.2 has an 11º by 4º intake valve angle and 8º exhaust. The intake valves centerlines were moved 0.250" closer to the intake flange and 0.080" toward the cylinder bore centerline.

We recommend a 2.15" intake valve and overall length of 5.65", and the exhaust valves were moved 0.014" outward. The spark plug holes were moved 0.125" toward the center of the bore for combustion efficiency. This head is redesigned to use shaft mounted aftermarket rocker arms, and the rocker cover rail was rolled five degrees toward the intake flange to increase clearance for the intake rocker arms. The valve spring pads were increased for use of 1.625" valve springs. Material has been added to the deck surface for a 48cc combustion chamber, and with a flat top piston it gives 12.1:1 compression. This head has been x-ray inspected to insure quality, then hot isostactic pressed.  
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12480021 Cylinder Head "SB2.2"      
This "CNC" SB2.2 aluminum small-block cylinder head is fully ported. It is the same as cylinder head P/N 12480011 except for the porting and beryllium copper valve seats and bronze valve guides.   Small Image
 

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12480092 Cast Iron High-Performance Head (Large Valve)      
This cylinder head (casting P/N 3991492) was originally installed on special high-performance small-blocks such as the 302ci Z-28 and 350ci LT-1. It is popularly known as the "fuel injection" head because it shares many features with previous high-performance Corvette heads. This head has straight spark plugs, 3/8" screw-in studs, pushrod guideplates, and heat riser passages. The 64cc combustion chambers are machined for 2.02" intake valves and 1.60" exhausts. Seats are not heat-treated.   Small Image
Technical Notes: The Cast Iron High-Performance Head (Large Valve) does not include 3/8" studs or guideplates.

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12480109 Cylinder Head, "Gen 3" V8 (LS1)      
The "Gen 3" V8 (RPO-LS1) engine is used in all 1997 and later Corvettes, and 1998 and later Camaros. This head is the same as the current production except it uses ASA springs and seats. These heads were designed for ASA type racing only. Use with "Gen 3" LS1 engines only.   Small Image
 

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12497186 Cylinder Head, "Fast Burn" Bare      
This Fast Burn head is identical to P/N 12464298 except that it has no valves, valve springs, or retainers.   Small Image
 

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12529093 Cast Iron Vortec Cylinder Head      
This bare head is identical to complete head assembly P/N 12558060 except it does not include intake valves, exhaust valves, springs, and retainers.   Small Image
 

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12556463 Corvette Aluminum Cylinder Head Assembly      
This aluminum cylinder head assembly for small-block Chevrolet V8s is ideal for street rods, fresh-water power boats, and high-performance applications. GM Performance Parts' aluminum cylinder head assembly combines the benefits of light weight, advanced design, and an affordable price. This complete head assembly includes valves, chrome silicon heavy-duty valve springs, retainers, 3/8" screw-in rocker studs-everything an enthusiast wants in a high-performance cylinder head package! GM Performance Parts aluminum cylinder head assemblies are based on brand new Corvette light alloy castings (P/N 10088113). The Corvette cylinder head's advanced design features include D-shaped exhaust ports that enhance the flow of burned gases, high-velocity intake runners that provide crisp throttle response, and centrally located spark plugs that improve combustion efficiency. Valve seat inserts for 1.94" diameter intake valves and 1.50" exhausts are installed in the 58cc combustion chambers. Raised rocker cover rails with machined sealing surfaces virtually eliminate rocker cover gasket oil leaks. This high-performance cylinder head assembly is used exclusively on High Output 5.7-liter small-block V8 engines. Unlike production Corvette cylinder heads, it is outfitted with special heavy-duty valve springs (see part number 12551483 for technical specifications). A pair of aluminum cylinder heads offers a weight savings of approximately 50 pounds over comparable cast iron cylinder heads. (A bare aluminum casting, less valves and springs, weighs 19 pounds, versus 44 pounds for a bare cast iron head). This reduction in total engine weight of 25 pounds each can improve handling, acceleration, and fuel economy.

Part Number...Description
12555269.........Stamped steel rocker cover
10229162.........Corvette screw-in oil filter 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  
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Technical Notes: Technical Notes: This casting does not have intake manifold heat riser or EGR passages. The exhaust port exits are approximately .100" higher than production cast iron heads; exhaust manifolds and aftermarket headers may require modification to maximize airflow. The spark plug holes are angled; check for adequate exhaust manifold or header clearance. Use 3/4" reach gasketed spark plugs with 5/8" hex heads (AC FR5LS), 904, or MR 43LTS. In rapid fire use #8 plug. Both ends of the head are machined for alternator, power steering, and air conditioning compressor mounts. No pushrod guideplates; use rail type rocker arms P/N 10089648. This aluminum head assembly requires valve covers with central hold-down bolts and extra-long bolts with washers. A composition head gasket with stainless steel fire rings is recommended to prevent galvanic action between the head and a cast iron engine block. This head assembly is the same as P/N 10185087, except valve spring and retainer change.

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12558060 Cast Iron Vortec Cylinder Head Assembly      
This production Vortec iron cylinder head was first used on the 1996 pickup truck RPO L31 with fuel injection. The intake and exhaust port are very similar to the Corvette 350 LT1 heads. This head includes 1.94" intake valves and 1.50" exhaust valves, with pressed-in 3/8" studs. This head with compatible valves flows more air than bow tie head P/N 10134392, but the casting may not be as durable. The water passages are the same as the original 1955 small block design. The eight-bolt intake bolt pattern is totally different than the early model V8 12-bolt design. Use new manifold P/N 12366573, 12496820, 12496822.   Small Image
Technical Notes: The valves seats in these heads can be machined to 2.02" intake and 1.60" exhaust. The rocker arm studs can be pinned or drilled and tapped 3/8". (Casting P/N 10239906 or 12558062.)

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24502517 Splayed-Valve Cylinder Head      
The splayed-valve cylinder head has 240cc intake runners. The splayed-valve casting has a .240" minimum port wall thickness that permits extensive modifications by cylinder head specialist seeking even more airflow. The intake valves are angled 16 degrees to the deck surface and tilted (splayed) 4 degrees. The exhaust valves are 11 degrees, with a 4 degree tilt. This cylinder head has symmetrical intake and exhaust ports and can accommodate a 2.20" diameter intake valve and a 1.65" exhaust valve. Its nominal combustion chamber volume is 45cc, although the actual volume will depend on the seats and valves installed.   Small Image
Technical Notes: Does not include seats or valve guides. The intake valve location moves the valve .050 closer to the bore center line than the earlier P/N 10185040. The following items are available from GM for the installation of this cylinder head: Rocker arm stand P/N 10185041, Intake gasket P/N 10185042, Rocker cover gasket P/N 10185043, and Rocker cover P/N 10185045. The intake manifold and remaining valvetrain components will have to be purchased in the aftermarket or be fabricated.

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24502559 SB2 Aluminum Racing Head      
These new SB2 (small block second generation) heads are designed for maximum effort competition, improved durability, simplified preparation procedures, and reduced overall cost of building and maintaining an S/B V8 racing engine. The intake valve ports are relocated to orient the intake runners toward the carburetor. The result is a distinctive "mirror port" arrangement that is a significant advance over conventional siamesed and symmetrical port designs. The exhaust ports remain in the traditional siamesed center port design with coolant passages between the ports that eliminate the need for additional machining and auxiliary water lines. SB2 heads provide "out of the box" airflow performance that is comparable with highly modified conventional castings. The revised valve layout improves valvetrain reliability by improving pushrod angularity and reducing or eliminating rocker arm offset. It also enhances piston durability by changing the depth and location of the valve pockets in the piston tops. The intake valve angles are 12º by 4º and the exhaust valve angles are 8º. The as-cast combustion chamber volume is 28cc; intake volume is 196cc. Recommended intake valves are 2.15" and exhaust valves 1.625" with valve length of 5.55" and valve seat intake 2.20" x .312" and exhaust 1.67" x .275".   Small Image
Technical Notes: A Special block P/N 24502600 (with revised lifter spacing/angles) is required only when using a flat tappet camshaft. These heads also require the following special components: upper intake manifold P/N 24502588, lifter valley cover P/N 24502587, spring oiler kit P/N 24502597, head gasket P/N 10185054 and rocker cover (not available). The following aftermarket items are available: head bolt kit from ARP P/N 234-4722; camshaft from crane flat tappet with 106º lobe separation P/N PL950266 and 109º lobe separation P/N PL950276 and roller cams are also available; rocker arms from Jesel; pistons from JE; special gaskets are required from Fel-Pro; valley cover P/N 1242; rocker cover P/N 1655; intake manifold, .030" thick P/N 1237, .045" thick P/N 1237-2, .060" thick P/N 1237-3, .090" P/N 1237-4, .120" thick P/N 1237-5. Wrench clearance for the nut on the short outer studs is limited. A 7/16" 12 point box end torque adapter (Mac Tools P/N XB142 with 3/8 drive) is recommended.

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24502560 SB2 "CNC Ported" Aluminum Racing Head      
The CNC ported cylinder head is the same as base head P/N 24502559 except it is CNC ported. See the Quick Reference Head Chart in this section for port volume and related information.   Small Image
 

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24502569 18º Cylinder Head, High Port Small-Block V8 - 9.1 Compression      
These aluminum 18º cylinder heads were released for Chevrolet 350, 9.1 compression NASCAR racing engines. These heads are similar to P/N 10134364, except they have an additional .080" on the deck and an added .055" to the intake manifold flange to maintain port alignment. To raise the compression to meet your need, you can machine the deck surface.   Small Image
Technical Notes: Specifications: Casting number is 10134363. Includes valve seats and valve guides. Valve spacing is 1.935". This head is recommended for cylinder bore diameter of 4.000"-4.155". Intake valve seat material is beryllium copper. Exhaust valve seat material is beryllium copper. Valve guide material is manganese bronze. Valve guide clearance ("Typical" valve stem diameters): intake is 0.0012" and exhaust is 0.0016". This head has 65cc chambers. Fully CNC ported. Required Components: Intake valve diameter is 2.15"; "back" angle is 12 degrees; length is 5.45" or 5.55". Exhaust valve diameter is 1.625"; "back" angle is 25 degrees; length is 5.45" or 5.55". Rocker arms (shaft mount): intake (with flat tappet) is 0.550" offset; intake (with offset roller lifter) is 0.450" offset; exhaust is 0.150" offset. Recommended Accessories: Intake manifold is P/N 10185053, 24502481, 24502487, or 24502579; intake manifold gasket set is P/N 10185007; head gasket is P/N 10185054; rocker cover P/N 10185064.

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24502580 Head, 18º V8 (9-1 Compression Ratio)      
Designed for 9:1 compression racing engines. Same as P/N 10134364 except it has extra .080" material added to deck to increase combustion chamber volume. It also has .055" material added to intake manifold flange to maintain port alignment.   Small Image
Technical Notes: This part uses casting P/N 10134363 and has semi-finished casting without seats and guides.

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24502582 18º Cylinder Head, High Port "Low Compression CNC"      
Fully ported CNC head for 9:1 applications similar to P/N 24502569, except with intake runners configured for 9:1 compression and 390 cfm carburetor. This head has beryllium copper intake valve seats and exhaust valve seats, and bronze valve guides. Fully CNC ported.   Small Image
Technical Notes: This part uses casting P/N 10134363.

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24502615 Aluminum Cylinder Head, 15º      
This new 15º aluminum cylinder head is designed for small displacement racing engines that run competition eliminator. This head is identical to the 18º head, except the head is rolled by machining the deck surface at a 2º angle and thereby removing more material from the exhaust side of the head than the intake side. The valve guide holes are also tipped 1º in the casting to produce a total of 3º in valve angle. Smaller combustion chambers are the main advantage. The head does not have valve seats or valve guides and has 35 to 37cc chambers instead of 42 to 44cc in the 18º head   Small Image
Technical Notes: P/N 24502615 is made from the same casting (101343633) as the 10134364. This is not a "CNC" ported cylinder head.

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12480034 Phase 2 Cast Iron Bow Tie Head      
The Phase 2 Bow Tie cylinder head (casting P/N12480034) has the highest performance potential of any cast iron Chevrolet head. It is intended for off-highway applications only. Although the Phase 2 cast iron Bow Tie cylinder head has the same casting number (12480034) as the Phase 1 head it replaced, there are several significant differences between these two heavy-duty cylinder heads. The Phase 2 cast iron Bow Tie head can be identified by its redesigned outer water jacket wall with a machined bar between the exhaust manifold flanges. (Phase 1 castings have a raised parting line between the exhaust manifold flanges.) The area around the tapped water temperature sensor hole is also machined flat on the Phase 2 head.

The Phase 2 Bow Tie head has a revised combustion chamber design with a true volume of 64ccs. The quench areas beneath the spark plugs are filled to increase compression in competition engines. The intake valve seats are machined for 2.02" diameter valves; the induction hardened exhaust valve seats are finished for 1.60" diameter valves.

The intake and exhaust ports are identical in Phase 1 and Phase 2 cast iron Bow Tie heads. The 184cc intake runners will satisfy the airflow requirements of most competition engines while enhancing throttle response and mid-range torque. In unmodified form, the Phase 2 Bow Tie head will flow more air than any production cast iron small-block head. Extra-thick wall sections allow the ports to be enlarged to increase their flow capacity. The manifold heat riser passages are deleted in Phase 2 Bow Tie heads to produce a cool, dense intake charge.  
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Technical Notes: The valve spring pockets in cast iron Bow Tie heads are machined for up to 1.50" diameter competition valve springs. The rocker stud bosses are tapped for screw-in studs; studs and pushrod guideplates are not included. Use GM Performance Parts studs P/N3973416 (3/8") or P/N3921912 (7/16") and hardened pushrod guideplates P/N3973418. Use 5/8" hex-head spark plugs with tapered seats and 3/8" reach. A bare casting weighs approximately 42 pounds. Valve seats are heat-treated.

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12480130 12480130 LS1 or LS6 Exhaust Header Flange      
This steel exhaust header flange is designed to make header for ASA race cars of street rods.   Small Image
 

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12480146 Splayed-Valve Cylinder Head ("Rough Machined")      
"The splayed-valve cylinder head has 240cc intake runners." The splayed-valve casting has a .240" minimum port wall thickness that permits extensive modifications by cylinder head specialist seeking even more airflow. The intake valves are angled 16º to the deck surface and tilted (splayed) 4º . The exhaust valves are 11º , with a 4º tilt. This cylinder head has symmetrical intake and exhaust ports and can accommodate a 2.20" diameter intake valve and a 1.65" exhaust valve. Its nominal combustion chamber volume is 45cc, although the actual volume will depend on the seats and valves installed.

It is the same as cylinder head P/N 24502517 except as follows: No head bolt holes, dowel holes, intake bolt holes, valve guide or seat machining, spark plug holes, valve spring seat machining, pushrod holes, or rocker bar machining. This gives maximum deck surface and the end surfaces are machined. (The difference between the rough machined P/N 12480146 and the semi-machined P/N 12480147 is the valve guide and spark plug holes are machined on P/N 12480147.)  
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Technical Notes: Does not include seats or valve guides. The intake valve location moves the valve .050 closer to the bore center line than the earlier P/N10185040. The following items are available from GM for the installation of this cylinder head: Rocker arm stand P/N10185041, Intake gasket P/N10185042, Rocker cover gasket P/N10185043, and Rocker cover P/N10185045. The intake manifold and remaining valvetrain components will have to be purchased in the aftermarket or be fabricated.

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12480147 12480147 Splayed-Valve Cylinder Head ("Semi-Finished")      
"The splayed-valve cylinder head has 240cc intake runners." The splayed-valve casting has a .240" minimum port wall thickness that permits extensive modifications by cylinder head specialist seeking even more airflow. The intake valves are angled 16º to the deck surface and tilted (splayed) 4º. The exhaust valves are 11º, with a 4º tilt. This cylinder head has symmetrical intake and exhaust ports and can accommodate a 2.20" diameter intake valve and a 1.65" exhaust valve. Its nominal combustion chamber volume is 45cc, although the actual volume will depend on the seats and valves installed.

It is the same as cylinder head P/N 24502517 except as follows: No head bolt holes, dowel holes, intake bolt holes, valve seat machining, valve spring seat machining, pushrod holes, or rocker bar machining. This gives maximum deck surface and the end surfaces are machined. (The difference between the rough machined P/N 12480146 and the semi-machined P/N 12480147 is the valve guide and spark plug holes are machined on P/N 12480147.)  
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Technical Notes: Does not include seats or valve guides. The intake valve location moves the valve .050 closer to the bore center line than the earlier P/N10185040. The following items are available from GM for the installation of this cylinder head: Rocker arm stand P/N10185041, Intake gasket P/N10185042, Rocker cover gasket P/N10185043, and Rocker cover P/N10185045. The intake manifold and remaining valvetrain components will have to be purchased in the aftermarket or be fabricated.

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12560801 12560801 LS6 "Gen 3" Performance Cylinder Head      
This cylinder head debuted on the 2001 LS6 Vortec engine. It offers the same overall package configuration as LS1 cylinder heads. However, the combustion chamber has been downsized approximately 3cc for more compression. Also, the exhaust port has been redesigned and features a raised floor and smaller port volume. This head is characterized by a "D" shaped exhaust opening at the exhaust flange.   Small Image
 

Modifier      
25534321 Cylinder Head (LS1 Showroom Stock Racing)      
This uses a production LS1 cylinder head (casting P/N 12559853) and has .035" machined off the deck surface to decrease it to 63cc chamber size. This raises the compression to 10.8:1. They also do a performance valve job with CNC porting with high lift valve springs P/N 12565117. Includes valves and springs.   Small Image
 


Small-Block V8 Cylinder Heads Quick Reference Chart

Part Number

Description

Casting Number

Material

Intake Runner Volume (cc)

Combustion Chamber Volume (cc)

Valve Diameter

 

Spark Plugs

Heat Risers

Notes

10125377

Cyl. Head w/Valves

14101083

Iron

-

64

I:
E

1.94"
1.50"

Straight

Yes

350 285 HP service head w/valves & springs.

10159552

Cyl. Head

14011083
14096217

Iron

-

64

I:
E

1.94"
1.50"

Straight

Yes

350 /300 HP

12480092

Service replacement

3991492

Cast iron

157

64

I:
E

2.02"
1.60"

Straight

Yes

Requires screw-in studs, pushrod guideplates.

12558060

L31 Service w/valves

10239906
or 12558062

Cast Iron

170

64

I:
E:

1.94"
1.50"

Straight

No

Vortec Design Port w/valves & springs.

12529093

L31 Service No valves

10239906
or 12558062

Cast Iron

170

64

I:
E:

1.94"
1.50"

Straight

No

Vortec Design Port less valves.

10134392

Bow Tie

14011034

Cast iron

184

64

I:
E:

2.02"
1.60"

Angled

No

Off-highway cast iron head.

12556463

Corvette Design for 350 HO service engine

10088113

Aluminum

163

58

I:
E:

1.94"
1.50"

Angled

No

Assembly with springs, valves, studs, and no guideplates

12363287

LT4 service only

NA

Aluminum

195

54.4

I:
E:

2.00"
1.55"

Angled

No

For LT1 or LT4 usage only.

12497186 Fast Burn No Valves 12367713 Aluminum 210 62 I:
E:
2.00"
1.55"
Angled No Fast Burn.  No valves.

12464298

Fast Burn w/valves

12367713

Aluminum

210

62

I:
E:

2.00"
1.55"

Angled

No

Fast Burn w/valves & springs.  Vortec design.

10051101

Raised Runner Bow Tie

10051101

Aluminum

196

55

NA

 

Angled

No

Intake ports are .200" higher than standard location; no seats, guides, and pushrod holes.

10033867

Pontiac Motorsports

10033867

Aluminum

196

62

I:
E:

2.100"
1.625"

Angled

No

Guides supplied but not installed

10134364

Bow Tie High-Port

10134363

Aluminum

210

42 to 44

NA

 

Angled

No

18 valve angle; no seats, guides.

24502569

CNC Machined

10134363

Aluminum

258

65

I:
E:

2.150"
1.620"

Angled

No

18 valve angle; for 9.1 compression

24502580

Bow Tie High-Port

10134363

Aluminum

215

60

NA

 

Angled

No

18valve angle; no seats, guides; for 9.1 engines.

12370855

Bow Tie High Port

10134363

Aluminum

215

60

NA

 

Angled

No

18valve angle; no seats, guides; for 9.1 engines x-ray head. Hipped.

24502582

Bow-Tie CNC High Port

10134363

Aluminum

245

65

I:
E:

2.150"
1.620"

Angled

No

18 CNC Ported

24502615

Bow-Tie

10134363

Aluminum

210

35 to 37

N/A

 

Angled

No

15 valve angle; no seats,guides.

24502517

Splayed Valve

10185040

Aluminum

240

45

NA

 

Angled

No design.

Splayed Valve

24502559

SB2

24502559

Aluminum

196

28

I:
E:

2.150"
1.625"

Angled

No

Intake valve at 12 & 4.

24502560

SB2 CNC Ported

24502559

Aluminum

280

38

I:
E:

2.150"
1.625"

Angled

No

Intake valve at 12 & 4.

12480011

SB2.2

12480011

Aluminum

284

48

 

 

Angled

No

8 Exhaust

12480021

SB2.2 CNC Ported

12480011

Aluminum

287

54

I:
E:

2.150"
1.625"

Angled

No

CNC w/seat & guides

12480005

LS1
GTZ

12480005

Aluminum

 

38

I:
E:

2.125"
1.625"

Angled

No

LS1 with revised ports.

12560801

LS6 Production Bare

 

Aluminum

200cc

67

I:
E:

2.000"
1.550"

Angled

No

No valves or springs.
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