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Parts


* P4876383 – CNC-Ported Stage VI Aluminum Cylinder Head (2.18" Intake, 1.81" Exhaust)


* P5153524 – Cylinder Head (“B/RB” Engines)


* P4529993 – Stage V Cast Iron Cylinder Head (2.14" Intake, 1.81" Exhaust) (Wedge)


*P5153524 – Cylinder Head (“B/RB” Engines)


* P5153349 – CNC-Ported Cylinder Heads (LH) 6.1L/392 HEMI * P5153350 – CNC-Ported Cylinder Heads (RH) 6.1L/392 HEMI


* P4529898 – Cast Iron Bare Machined Head (426 HEMI) * P4876855 – Cast Iron Cylinder Head Assembly (426 HEMI Crate Engine)



* P5007708AB – W2 Cast Iron Race Cylinder Head (2.02" Intake (48° 47 cc), 1.60" Exhaust) (Revised Intake Ports) * P5007445AB – W2 Cast Iron Race Cylinder Head (2.02" Intake (48° 65 cc), 1.60" Exhaust) (Revised Intake Ports) * Not legal for sale on pollution-controlled vehicles or vehicles registered for highway use.

PURE PERFORMANCE HEADS

Engines have always been the most popular aspects of performance cars and cylinder heads are the most popular engine part. Heads aren't the largest, or the heaviest or the most expensive engine part but some versions can be expensive. In the Muscle Car era, you tended to only have one or two choices for cylinder heads: the stock, production head and perhaps a large-valve version of the stock head or HP option that also fit your engine. Each engine family tended to have an option or two but it wasn't too complicated. This has all changed over the last 20 years and now there are so many cylinder head choices that the selection can be very difficult. Cylinder heads are constantly evolving for many different reasons. Part numbers change, features are added, or back-orders and supplier issues may be resolved or all of the above.

On the 426 HEMI®, called Gen II today, there's a new aluminum head, P5153779 (new part number) which takes about 50 lbs. off the engine's weight compared to a pair of cast iron production heads. They have 170 cc chambers and stock 2.25"/1.94" valve sizes like the originals. There is also an assembly P5153875 (new part number) which includes valves, springs, keepers and retainers, and is the head used on the 528 HEMI Crate engine. The cast iron 426 HEMI heads are also new and in stock and they use the same part numbers: P4529898 bare, and P4876855 assembled.

The 5.7L and 6.1L HEMI engines are considered Gen III HEMIs and the special CNC-ported heads, assembled with stainless-steel valves P5153349 and P5153350 as used on the 6.1L and 392 HP Crate engines are available. The Gen III HEMI uses a left and right cylinder head so they should be purchased/ swapped in sets.

The typical big block Mopar® is a 383 (low block) or 440 (raised block) but they use the same cylinder heads with unique intake manifolds. The current aluminum big block head is an assembly P5153524 (includes valves, springs etc.) and features a straight spark plug, similar to production, has 2.14" intake valves and 1.81" exhaust valves, flows 290 cfm on the intake at .600" valve lift (very good number) and has an 84 cc combustion chamber size. Additionally, there is a new raised-port Stage VII aluminum big block head P5153654 based on 2.20" intake valves, a larger 280 cc intake port and improved intake flow. My favorite CNC-ported aluminum big block head is P4876383. It is based on 2.18" intake valves and 1.81" exhaust valves and a 260 cc intake port and it flows well over 300 cfm at .500" valve lift (the reason it is my favorite).

Tip: Remember that most all aluminum cylinder heads save about 50 lbs. per set compared to typical cast iron heads. Aluminum heads also use valve-guide and valve-seat inserts on both intake and exhaust sides. These inserts are pressed into the aluminum head casting. Like all aluminum heads, the aluminum material conducts heat away from the combustion chamber and acts to lower the engine's effective compression ratio. You want to account for this loss in your calculations. It is more noticeable at 9 and 10-to-1 ratios than at higher ones.

On the cast iron big block cylinder head front, there are nice new castings for the big-port, Max Wedge heads. The NHRA/IHRA Stock or Restoration head for the 413/426 Max Wedge engines is P5007494 and features 2.08" intake valves and 1.88" exhaust valves. The big valve version of this head is P5249824 and uses 2.14" intake and 1.81" exhaust sizes. Either head will fit on street/bracket big blocks (440s) but the big valve version flows better out of the box so it would be the better choice for these applications. The high performance, resto and almost any other big block application that requires a stock sized port in the head to match stock-sized intake manifold ports will use the cast iron Stage V head P4529993 which is based in 2.14" intake valves and 1.81" exhaust valves. The stock valve sizes were 2.08" and 1.74" and most customers request the larger valve sizes because they allow for more air flow.

Ported cylinder heads have been around for many, many years. CNC-ported heads only date from perhaps the past 20 years. However CNC-ported heads seem to be much more popular than any other ported version. Most CNC-porting services focus on aluminum heads. Additionally, CNC-porting services like to have an aluminum head that is designed for CNC-porting. These types of aluminum heads have a lot of extra material around the ports which tends to make them heavy and not useable in the as-cast-port condition. Only a few CNC-porting services will use cast iron heads and street-type aluminum heads. A CNC-porting service has to first input all the basic data – valve locations and angle, port faces, seat height, etc. and then they must digitize a port that will fit into the existing casting and flow the desired amount of air.

The head situation relating to the Mopar small blocks is the most confusing because there have been lots of changes. The current aluminum head for the Magnum® engines (generally called 5.2L and 5.9L engines) is P5153847 and it is an assembly which has 2.02"/1.60" valves and a 58 cc chamber. It flows slightly better numbers than earlier versions, mainly due to machining in the bowl area and at the manifold face, which makes the heads look pretty and also happens to help the flow numbers.

The LA-engine, Mopar small block (typically listed as 318-340-360 engines) aluminum cylinder head is P5153849 and has a chamber size of 63 cc. Similar to the Magnum version, this LA-engine head flows slightly better numbers than earlier versions but this gain is mainly due to bowl and manifold-face machining which makes them look pretty and also happens to help the flow numbers.

Small-block cast-iron heads are getting hard to find new. Perhaps this situation is better stated as cast-iron heads are getting hard to make. There are very few cast iron foundries in this country that can cast an iron part as large as a cylinder head. Add to this that a cylinder head is one of the hardest parts to cast because of the ports and water-jacket. However, today there are brand-new W2 cast iron heads that are made from a complete 3-D computer model of the W2 design and these heads are the most accurate W2 heads that have ever been made. There are several race versions of this basic W2 head: P5007708AB – 48-degree block, 47 cc chamber and P5007445AB – 48-degree block and 65 cc chamber. I would expect more versions to be added in the future.

Note: Engine projects using cylinder heads mentioned in this article may require additional parts to complete the job. There may be special intake manifolds required, special intake gaskets, valves and springs, rocker arms, shafts, stands, breast plates or valley trays, or head bolts. Space limitations do not permit coverage of all these aspects; therefore, please check for details in the latest MP catalog Click here.

Courtesy of Mopar Magazine

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