Cylinder heads are one of the keys to great performance on any stroker engine. The large-displacement stroker engine demands very good cylinder head airflow to make big power. But great-flowing heads only work when they are used with the other components designed to work together (i.e., camshaft, intake manifold, and headers).
Iron vs. Aluminum
The choice between cast-iron and aluminum heads is based on cost and weight. High-performance iron and aluminum heads are readily available and they both offer great performance in stroker engines.
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Aluminum heads reduce the weight of the engine by about 50 lbs. Most aluminum heads are more expensive than iron heads. Aluminum heads are also easier to fix if they ever become cracked and need to be welded.
Cast-iron heads don’t transfer as much heat from combustion to the coolant, making them slightly more efficient. This is the reason why engines with aluminum heads generally use a slightly higher compression ratio than a similar engine with iron heads. For example, an engine with iron heads should use a 9:1 compression ratio on pump gas, where the same engine can run 10:1 compression with aluminum heads. Combustion and heat are the way fuel is transferred into mechanical power.
All production LA and Magnum heads have an 18-degree valve angle. This valve angle is lower than most other cylinder heads for small-block engines (i.e., most GM heads are 23 degree). In general, when the valve is stood up or made closer to a zero angle, airflow is improved. The fuel and air mixture does not have to turn as sharply when entering the engine through the intake port, and this helps flow.
Most high-performance cylinder heads for Mopar engines also use the 18-degree valve angle. The only ones that have a slightly better valve angle are some versions of the W2 and all W7, W8, and W9 cylinder heads. These heads use a 15-degree valve angle for better airflow. The 15-degree heads are also designed for use with 48-degree tappet bore blocks. One version of the standard W9 and the W9-RP (raised port heads) use a 13-degree valve angle. See Chapter 3 for more information on 48-degree tappet bore blocks.
When the valve angle is changed from the stock 18-degree, the notches in the pistons must be machined to match that valve angle. If the piston machining is not changed, any valve contact with the piston bends the valves since they won’t hit square in the notch. Granted, the valves should never touch the piston, but it can happen if the engine is over revved and valve float occurs.
A Heads vs. Magnum Heads
What are the major differences and V Vsimilarities between LA and Magnum cylinder heads?
- Same cylinder head bolt pattern (4-bolt)
- Same valve spacing and valve window
- Same 18-degree valve angle
- Same intake port location (very minor differences in port size & shape)
- Same exhaust flange bolt pattern
- Same type of spark plugs
- Same water outlets – on each end of the cylinder head
|Valve Cover Shape||Curved at Ends||Square at Ends|
|Valve Cover Bolt Pattern||5-bolt||10-bolt|
|Valve Stem Size||3/8”||8mm|
|Intake Screw Angle||Standard||Vertical|
|Rocker Arm / Valvespring Oiling||Through Block/Heads||Hollow Pushrods|
|Rocker Arm Type||Shaft Mounted||Stud Mounted|
|Intake Valve Sizes||1.880”/2.020”||1.920”|
|Exhaust Valve Sizes||1.600”||1.625”|
|Combustion Chamber Size||70cc||60cc|
|Approximate Intake Airflow||160 cfm||190 cfm|
|Exhaust Heat Crossover||Center of Head||None|
|Coolant Heat Crossover||Center of Head||None|
|Accessory Mounting Holes — end of head||3-bolt||5-bolt|
Most Mopar cylinder heads have 1.870” between the centerline of the valves in each cylinder. This spacing allows maximum valve sizes of up to about 2.080” on the intake valve with 1.600” exhaust valves. Any valves larger than this require offset valve guides or the reduction in size of either the intake or exhaust valve.
W7, W8, and W9 heads have spacing of 1.936” between the valves. This extra room allows much more room for larger valves. It also allows up to 2.200” intake and 1.600” exhaust valves. These larger valves allow the extra airflow to feed a very large stroker engine. Most engines over 420 cubes need large valves to flow enough air to make good power. Think of it this way: if your stroker engine has big-block sized cubic inches, then you need big-block sized valves (i.e., 2.100” to 2.200” intake valves).
Ports & Chambers
The most important area on any cylinder head is the intake and exhaust ports and chamber. The shape and design of the ports control how the air/fuel mixture and combustion performs as it goes into and exits the cylinder.
Most manufacturers publish port volumes to give an idea of the size of the ports on a cylinder head. This data provides some information, but the cross-sectional area (width of the port) is also an important factor. Don’t compare Mopar heads with GM or other heads by port volume, since the length of the ports are not the same. For example, a longer port has more volume, but it isn’t really any larger. Also, remember that different Mopar heads have different port lengths, and they don’t have the intake surface in the same place relative to the bore on all heads. Due to these changes, you cannot directly compare Mopar heads with port volume since the port length is not always the same.
Most stock production heads flow about 160 to 190 cfm on the intake port. High-performance heads offer intake flow from about 200 to 300 cfm “as cast,” or more with porting.
LA vs. Magnum Valve Spacing
Most Mopar cylinder heads have 1.870” between the centerline of the valves for each cylinder. This works well for most heads but limits valve sizes to about 2.080” on the intake and 1.600” on the exhaust. To use larger valves, the valves must be spaced farther apart.
Sometimes the valves can be used with offset valve guides to allow more room for a larger intake valve. Often the exhaust valve is reduced in size to allow a larger intake valve. These changes may help, but they may cause other problems since the valve is no longer located in the center of the port. Reduction in the size of the exhaust valve may cause an imbalance in flow since the exhaust valve may get too small for balanced intake to exhaust flow.
Large-displacement stroker engines should use large valves that flow enough air to make optimum performance. Any engine with over 420ci should use 2.100”, 2.150”, 2.180”, or 2.200” intake valves, and cylinder heads with large ports that flow enough air to support the large engine. The best choices for big-inch stroker engines are W9, Indy, and Brodix heads.
|Valve Spacing by Cylinder Head:|
|Cylinder Head||Valve Spacing||Largest Valve Size intake/exhaust)||Space Between Valves|
|Prod. LA Heads||1.870”||2.080” / 1.600”||0.030”|
|Prod. Magnum Heads||1.870”||2.020” / 1.625”||0.048”|
|Aluminum Magnum Heads||1.870”||2.020” / 1.625”||0.048”|
|R/T Heads||1.870”||2.020” / 1.625”||0.048”|
|W2 Heads||1.870”||2.080” / 1.600”||0.030”|
|W7 Heads||1.936”||2.200” / 1.600”||0.046”|
|W8 Heads||1.936”||2.200” / 1.600”||0.046”|
|W9 Heads||1.936”||2.200” / 1.600”||0.046”|
|Edelbrock Heads||1.870”||2.020” / 1.600”||0.060”|
|Brodix B1BA & SP MO||1.870”||2.080” / 1.600”||0.030”|
|Indy Heads||1.870”||2.100” / 1.650”||offset guides|
The general rule of the thumb regarding airflow is that the engine has the potential to make about 2 hp for each CFM of intake airflow. The other component parts of the engine must be working in harmony to get this output, but it gives a good idea of what the potential output could be. So a cylinder head that flows 200 cfm may make about 400 hp, and one with 300 cfm may make about 600 hp.
The camshaft must be designed to complement the airflow performance of the cylinder heads. For example, most Magnum heads flow pretty good up to about 0.550” valve lift. The desired valve lift to work with these heads should probably be in the range of 0.475” to 0.525” to perform properly with these heads. A camshaft with valves opened to 0.600” or more would not work well since the heads cannot flow in this lift range.
Study the manufacturer’s flow data and consider getting additional data from a second independent source if possible. Remember, not all flow benches work the same way or provide consistent data. Many flow benches are homemade and don’t correlate with other benches. Sometimes the test procedures are also different, and some give higher numbers based on the procedure changes.
Cylinder Head Selection
Mopar LA Cylinder Heads
The specifications for these heads are shown in the chart listed above. Notes on the special features and comments are shown for each head below. Be sure to select a cylinder head that works with the tappet angle of your block. The tappet angle is shown below in parentheses after each cylinder head (in the heading).
LA Production Heads – Cast Iron (59 degree blocks): 273 and 318 heads have very small ports and small valves. These heads don’t offer much performance potential and should not be used on a stroker engine.
340 and 360 LA heads have larger intake ports and are the only production LA heads worth using on a stroker engine. 340 heads have a larger intake valve with a 2.020” size. 360 heads use a 1.880” intake valve, but they can be re-machined for use with 2.020” valves.
LA heads cannot be used on Magnum blocks since there is no oil passage to feed up through the block to the heads. This oil passage can be drilled in a Magnum block, but this must be done by an experienced machinist.
With some porting work, LA heads work well on most stroker engines up to about 418ci. LA heads are probably the least expensive heads out there, but they are only available used at this time. Mopar previously sold these heads, but they have now sold out of them and can’t get any more.
W2 – Cast Iron (different versions for 48 and 59 degree blocks): W2 cylinder heads flow the most air of any iron Mopar cylinder head (about 260-265 cfm on the intake port). The most unique feature of the W2 heads is the oval-shaped intake port. The intake ports are raised and must be used with special W2 intake manifolds that have the oval ports. The bolt pattern on the W2 is also spaced out farther from the ports, and is not the same as standard LA intakes.
These heads are best suited for oval-track racing and drag racing. The valve gear is pretty expensive, since T&D rocker arms are required for most W2 heads made since 1/10/02. Early heads are prone to cracking when milled too thin, but changes made in about 1998 added ribs that made the heads stronger.
Commando – Aluminum (59 degree blocks): Commando heads are offered with two different intake ports sizes. The standard port heads (P4876785) are a direct replacement for the iron LA heads. They use the same valves, intake, rocker arms, valve covers, and all other parts. The only special change is that larger oil passages must be drilled in the underside of the rocker shafts. The holes should be drilled around two of the rocker shaft screws for oil flow (drill to 7/16” diameter). These heads use 3/8” rocker shaft bolts, and this requires modification to the rocker shaft.
The large port Commando heads (P4876310) have a significantly larger intake port. Because the ports are so large, you must use W2 style rocker arms with more offset to clear the intake ports. All other components are the same as a standard LA head (i.e., valves, springs, LA intake manifold, etc.). The ports are large enough to see the pushrods in the intake screw holes. Use a little RTV on the intake screw thread near the intake ports to prevent leakage at the intake screws.
Commando heads are made using the same casting as the aluminum Magnum. The only difference between these heads is in the machining. This common casting has a bump or boss inside the top of the intake ports. This boss allows enough material for the rocker arm screws on the aluminum Magnum, but it is not needed on the Commando heads. This extra bump can be ground out of the port on Commando heads (not needed and this helps airflow slightly).
W9 – Aluminum (48 degree blocks): W9 heads have the most performance potential for very large stroker engines (over 420ci). These heads have huge intake ports that flow over 300 cfm “as cast.” The wide valve spacing allows the use of large intake valves up to 2.200”. The exhaust port is very efficient and doesn’t need to be larger than 1.600” or 1.625” even on the largest displacement engines.
P5007065AB is for use with 48-degree blocks only. To allow flexibility in selecting the valve sizes, this head does not have the valve job done. The guides are designed for 11/32” valve stems. Most engine builders use Manley +0.600” long GM valves (i.e., Manley #11766-8 2.150” intake and #11767-8 1.600” exhaust). The +0.600 long” indicates generic racing (small-block Chevy) valves that are 0.600” longer than stock. The actual length of these valves is 5.540” on the intake and 5.560” on the exhaust.
P5007065AB has a CNC-machined chamber designed for use with gasoline. The chamber machining un-shrouds the spark plug, and the spark plug machining allows the use of common 3/4” reach spark plugs.
W9 heads must be used with T&D rocker arms. Though expensive, these rocker arms are very high-quality parts designed for racing and HP applications. The rocker-arm’s screw holes go right into the intake ports. This looks funny but doesn’t hurt anything, and you should use Loctite or another fuel-resistant sealant on the threads of the rocker stand screws.
The valvesprings are very close to the valve cover on the W9. This means trimming must be done on the valve cover gasket for spring clearance. The valve covers must also be wider than stock for valvespring clearance. Valve cover set P4876124 uses sand-cast covers that have the rail rolled inward for extra clearance. Some grinding may still be necessary on the valve covers for spring clearance. Custom fabricated W9 aluminum valve covers are also available from Moroso. Carbon fiber valve covers are available from Crawford & Crawford Composites.
W9 – Aluminum (59 degree block): The version of the W9 that works on 59-degree blocks is P4510324. This head has been modified for pushrod clearance on a 59-degree block. This modification removes material from the outside of the intake ports, and this limits the amount of porting than can be done. This head is delivered with the valve job machined and is recommended for use with 3/8” stem valves P4876580 (2.15” intake) and P5249886 (1.600” exhaust).
The combustion chamber on this head is CNC machined to unshroud the spark plugs for better performance. Use extended-tip spark plugs with W9 heads for best performance (i.e., Champion racing plug C59YC or C61YC to add 5 to 10 hp).
The outer edge of the extra head bolts has been machined away since the bolts cannot be used on 59-degree blocks. This makes the heads look better since the extra holes look funny without any studs or bolts there.
Most versions of the W9 heads use a 15-degree valve angle. Be sure to use pistons that have valve notches with the 15-degree angle to match the valves. You could machine pistons to change the valve angle from the standard 18 degrees to 15 degrees. This machining may reduce the compression ratio of the piston/combination.
Aftermarket LA Cylinder Heads
Several other sources for LA cylinder heads can be found in the aftermarket.
Edelbrock – Aluminum (59 degree blocks): Edelbrock offers two versions of its Chrysler heads with slightly different combustion chamber sizes. The Performer RPM 340 has a slightly larger chamber size. It is designed for use on higher-compression 340 engines that need more clearance from the piston to the chamber. The Performer RPM Chrysler version works on all other engines with dished or flat-top pistons.
These heads use special Edelbrock 11/32” stem valves (2.020” intake and 1.600” exhaust valves), and they require special head bolts. All other stock parts can be used (i.e., rocker arms, valve covers, and intake manifolds). Edelbrock heads cannot be used on Magnum short blocks since they use the stock LA oiling system that requires oil passages through the block to the head.
Brodix – Aluminum (59 degree blocks): Brodix heads are designed primarily for oval track and drag racing. Two different versions are available with different intake port sizes and different valve spacing.
The B1 BA heads use standard intakes, headers, and valve covers. Standard LA rocker arms may be used, but they require the use of special B1 rocker stands. GM rocker arms may also be used when the heads are oiled through the tappets and hollow pushrods. Custom guide plates must be fabricated for use with the GM rocker arms.
The B1 BA MC has a larger intake port and must be used with a W5 or W7 intake manifold. The exhaust header bolts are not machined – this is to leave flexibility in what can be used. An after-market shaft-mount racing rocker arm set is required (i.e., T&D). Machining may be required for pushrod clearance. The valve spacing is wider than stock and can be used with 2.140” intake and 1.600” exhaust valves.
Indy – Aluminum (59 degree blocks): Indy offers two different versions of its 360 aluminum heads. These heads have the six-head bolt pattern with two extra head bolts per cylinder. The problem is they are designed for a 59-degree block with an 18-degree valve angle. 59-degree blocks don’t have two extra head bolts per cylinder, so the extra head bolts are not used. These heads come with two exhaust bolt patterns, one for the LA and one for the W2 header bolt pattern.
The 360-1 has rectangular intake ports and is usually sold in kit form including all parts between the block and carburetor. The recommended intake manifold for this head is Indy #360-R3, and it is designed for use with 0.800” offset Indy rocker arms. Indy recommends this head for 360- to 426-ci engines.
360-2 is similar but has oval-shaped intake ports. This head is also sold in kit form, but it can be used with an Indy or W2 intake manifold. Indy recommends this head for 318- to 370-ci engines.
Magnum heads are designed for use on 1992-’98 5.2L and 1993-’03 5.9L engines. These heads can also be installed on any LA and offer an inexpensive way to build good power. See the special section of this chapter that explains how to install Magnum heads on an LA short block.
Magnum heads use stud-mounted rocker arms and must be oiled through the tappets and pushrods. Magnum heads use the 10-bolt valve cover. All Magnum heads except P5007950 use vertical intake screws that are different from the LA side-mounted intake screws.
Magnum Production (59 degree blocks): The intake port of the production cast-iron Magnum heads flow more air through the “as cast” ports than any other production Mopar small-block head. The intake port flows about 30 cfm more than any LA cylinder head. The exhaust port is not quite as good as the best LA heads.
Since the Magnum exhaust port does not flow as well as some LA heads, the camshaft should add more lift and duration to the exhaust for optimal performance. Increase the exhaust lift by about 0.010” to 0.030” and about four degrees duration (more than on the intake).
Production Magnum heads are prone to crack on the exhaust seats between the valves. Check used heads carefully for any cracks. Stock production Magnum heads are no longer available new from Mopar or your Dodge/Jeep/Chrysler car dealer. Most cracked heads are now replaced with the Magnum R/T cylinder head P5007140.
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5.2L and 5.9L production heads are about the same. Both use the same valve sizes and all other component parts. The 5.2L and 5.9L castings were made in two different foundries, so the casting itself has some very minor differences, but nothing significant. Mopar sold both of the Magnum castings as service parts for both 5.2L and 5.9L engines (based on availability).
Magnum R/T (59 degree blocks): The Magnum R/T was developed as a heavy-duty HP cylinder head for Magnum engines. The R/T heads have better ports, and this gives a stock engine an extra 20 hp and 9 ft-lbs torque by installing these heads (as compared to stock Magnum heads). The performance gains are even higher when compared to LA heads.
P5007140 is fully interchangeable with all stock Magnum components (i.e., valves, springs, retainers, keepers, valve covers, etc.). P5007141 is the same except that it uses a larger 2.020” intake valve. The large-valve version of this head is a better choice for most stroker engines. P5007145 is the same as P5007140 (smaller valve), but it comes as a complete assembly with valves, HP valvesprings, and all component parts.
R/T heads have larger than stock ports, and this leaves less room for the intake screws since they mount on the top of the head above the ports. The stock rocker-arm screws are too long and bottom-out in the intake screw holes. A shorter 5/16” × 1.5” long grade 8 bolt with a lock washer should be used for the rocker arms (16 pieces needed). The stock bolt can also be used if a 1/16”-thick washer is also installed, but these screws are not as strong as the grade 8 bolts.
LA Replacement Head (59 degree blocks): LA replacement heads are the same as the big-valve Magnum R/T P5007141, except they have been machined for use with an LA intake manifold. The intake screws are drilled and tapped at the standard LA angle so that more intakes fit. All other components such as the valves, springs, retainers, and other parts are stock Magnum. The intake valve is a large 2.020” size, use Mopar valve #P5249878.
These heads can be used on Magnum blocks where another intake is desired (i.e., Edelbrock, Six-Pack, stock LA, or other manifold). Because of the limited selection of Magnum intakes, this head allows the option of more choices using LA intakes.
The Magnum intake port is slightly taller and narrower than an LA intake, but they are both very close in size. Minor grinding can be done to match these ports. Use an intake manifold gasket as a template for the port matching.
These can also be used on LA blocks by using tappets and pushrods that oil the heads. See the instructions in this chapter for installing Magnum heads on an LA engine.
Aluminum Magnum (59 degree blocks): The aluminum Magnum is a HP aluminum version of the Magnum head. The aluminum heads reduce the engine weight by about 50 lbs. These heads have improved intake and exhaust ports, and they provide a 15- to 20-hp gain over stock production Magnum heads.
Most all-stock Magnum component parts fit these heads. The only difference is the rocker-arms screws, which are a larger 3/8” size (use 3/8” – 1.75” grade 8 bolts). The larger size is needed to provide strength in the aluminum casting. The larger screws require rocker arm pivots with the larger 3/8” hole in the center (package of 16 pieces – P4876514). The guide plates must also be drilled out to work with the larger 3/8” rocker bolts.
Magnum Heads with an LA Intake Manifold
You can use an LA intake manifold Y with Magnum cylinder heads two different ways.
The first way is to have the heads re-machined to add a second set of tapped intake screw holes on the Magnum cylinder heads. This can be done using a mill at an experienced machine shop.
These extra tapped holes must be machined using a mill since they are being started inside the hole for the existing vertical screw holes. Hughes Engines, Inc. can drill and tap your Magnum heads for the LA intake manifold bolt pattern. The cost to machine these extra holes is $64.00 for each pair of cylinder heads. After this machining, the heads can be used with both the Magnum and LA intake manifolds. See Appendix B for the address and phone number for Hughes Engines.
Another solution to this problem is to use the new LA replacement head from Mopar Performance Parts (P5007950). This head is a Magnum R/T head, but it is machined for use with LA intake manifolds (standard LA intake screw holes only).
This cylinder head allows the use of any LA intake manifold and provides the performance features of the R/T (i.e., more airflow, lighter valves, inexpensive rocker arms, increased compression ratio, big valves, and better valve cover seal).
This head requires the use of hollow pushrods and tappets that have oil passages to oil the top of the engine. See the section in this chapter that shows the detail on installing Magnum heads on LA engines.
This head can also be used on Magnum engines without any changes, except for the LA intake. This allows intake options that were never available before (i.e., Six-Pack, Edelbrock, or other special intakes not available for Magnum heads).
These methods can be used in racing classes that require cast-iron heads and intakes. The Magnum heads offer good performance potential, but no cast-iron intakes will fit Magnum heads. Cast-iron intakes were never made for Magnum engines, so only LA iron intakes are available. A used stock cast-iron intake is easy to install on Magnum heads using the two methods shown above.
Aftermarket Magnum Heads
ProTopline Magnum (59 degree blocks): ProTopline produces the only aftermarket iron Magnum head. Based in New Zealand, the company was in receivership due to financial problems and not operating at the time this book was written.
Currently, bankers controlling the company are selling some of ProTo-pline’s heads. The heads are stock-replacement cast-iron. These heads use all the stock component parts.
Edelbrock Magnum (59 degree blocks): Edelbrock also offers an aluminum head to fit Magnum engines. These heads use 2.020”/1.600” valves with an 11/32” valve stem. These heads feature 3/8” rocker studs with guide plates. The larger-diameter rocker studs require modification to the rocker arms since Magnum heads normally use 5/16” studs/bolts.
Other Used Heads
The following heads are no longer available new, but they may be available used. Be sure to thoroughly check any used heads for signs of damage before buying them. The casting numbers shown in this chapter can help when identifying used heads. Mopar doesn’t sell heads by the casting number in most cases, so the cross-reference chart is needed.
Installing Magnum Heads on an LA Short Block
Many people want to know how they can install the later-style Magnum heads (1992-2003) on an earlier LA short block (1967-1992). The increased airflow of the Magnum heads leads to performance gains of 20 to 50 hp without any porting, depending on the head selected and the heads previously used. The increase in intake airflow is from 20 to 60 cfm, and this is the reason for the substantial performance gains.
Some of the common reasons are listed below:
- Magnum heads flow more air and this creates more HP.
- LA cast iron heads are getting difficult to find in good condition. Inexpensive valvetrain options.
- Improved cylinder-head oiling.
- Better valve cover seal using 10-bolt Magnum valve covers.
- Slight increase in compression ratio.
- Larger and lighter valves.
These instructions apply to all Magnum cylinder heads when installing them on an LA short block. Magnum head choices include: 1992-’03 production Magnum heads, aluminum Magnum heads (P4876624), Magnum R/T cylinder heads (P5007140, P5007141, P5007145), and LA replacement heads (P5007950).
The Magnum heads use the same cylinder head-bolt pattern as LA heads, so they bolt on pretty easily. The exhaust header bolt pattern is also the same, so headers and exhaust manifolds bolt on without any problems. The rocker arms, valve covers, valves, pushrods, valvesprings, retainers, keepers, and valve seals are different, so Magnum parts must be used for these components.
Most Magnum cylinder heads use vertically mounted intake manifold screws instead of the traditional screws that go directly into the side of the head. This requires a change to the Magnum intake manifold that is set up for use with the vertical screws. The one exception to this change for the LA replacement head P5007950 is that the head is specially machined for use with the LA-style intake screws (not vertical screws). If you want to use an LA manifold that you already have or a manifold that does not fit the Magnum heads, use P5007950.
The trick to installing the Magnum heads on an LA block is to use tappets that have oil passages and hollow pushrods to provide oil to the heads. AMC (American Motors 360-401 V-8, or Jeep 4.0L I-6) flat tappets are the same diameter as LA tappets and have the needed oil passages. These hydraulic tappets are available from Mopar, part number P4529220AB, and are also available from most mailorder and cam suppliers. COMP Cams also sells mechanical (solid) tappets with these oil passages (part number 801-16).
The pushrods must be 5/16” diameter to fit through the heads, and hollow to allow oil flow to the heads. The pushrods must be 7.625” long when using hydraulic tappets P4529220AB, and the stock production Magnum rocker arms (where the heads and block have not been milled). This length works with most HP hydraulic flat tappet camshafts. These pushrods are available from Mopar, part number P5007477 (set of 16).
The head gasket and Magnum heads block off the unused oil passages that come up through the deck on the block. You can tap and install allen-head style plugs to cover these unused oil passages, but the engine must be completely disassembled to get the block clean after drilling and tapping the oil passages at the deck (see Chapter 5 for more information on plugging these holes). I have built several engines without plugging these holes and have not had any problems with oil leaks at the deck.
The Magnum cylinder heads have a smaller combustion chamber (60cc with iron heads, and 53cc on the aluminum Magnum) than LA heads, and this increases the compression ratio by about one point. With most stock engines this is a plus from a performance standpoint, as long as the compression ratio doesn’t get too high for use with pump gas. If you don’t want the increase in compression ratio, consider using thicker head gaskets. Thicker head gaskets (up to 0.120” thick) are available from Cometic Gasket. You should use flat-top or dished pistons to avoid any interference with the closed combustion chamber on the Magnum heads.
The recommended parts when installing Magnum heads on an LA block are listed below:
The stock Magnum production valvesprings and retainers also work, but the springs are a beehive design, and this makes the retainer too small for use with HP springs. The best bet is to use P5249464 and P4452032 in high-performance applications (listed above).
Another way to save some money is to get a set of used production Magnum cylinder heads (i.e., 1992-’98 5.2L or 1993-’03 5.9L heads). Be sure to get the valve covers, rocker arms, and all other hardware that can be reused. Thoroughly inspect any used production Magnum heads, since they are prone to crack. The cracks are normally between the valve seats. You may have to remove the valves to inspect for cracks. If the heads are cracked they are probably junk, as they are expensive to repair.
The cylinder heads oiling method shown above can also be used with other heads that oil through the tappets and pushrods (i.e., W8, W9, and some versions of the W2). These heads use different rocker arms and valve-gear, so it would be best to mock-up the engine and measure the exact pushrod length and custom order the pushrods for the application.
|Your Choice||1||Hydraulic flat tappet camshaft for LA engine|
|P4529220AB||16||AMC Hydraulic tappet|
|P4876050||8||Production Magnum Rocker Arm (or Prod. Magnum)|
|P5007477||1||Hollow Pushrod Set – 7.625” long|
|P4452032||16||HP Chrome Moly Retainer|
|P5249464||16||HP Valvespring – up to 0.525” lift|
|P4529218||2||Valve Locks (or Prod. Magnum)|
|P5249661||1||Valve Seals (or Prod. Magnum)|
|P5249876||8||Exhaust Valve – 1.625” (or Prod. Magnum)|
|P5249875||8||Intake Valve – 1.92” (or Prod. Magnum)|
|or P5249878||Intake Valve – 2.02” with heads P5007141 or P5007950|
|P5007617||1||Die Cast Valve Cover Set (or Prod. Magnum)|
|P5249660||1||HP Valve Cover Gasket set (or Prod. Magnum)|
|P4876759||1||Head Bolt Set (or Prod. Magnum)|
|P4876049||1||Intake Manifold gasket set (or Prod. Magnum)|
High-Performance Cylinder Head Casting Numbers
The chart listed below helps to identify most HP cylinder heads by the casting number. Most Mopar Performance cylinder heads are not sold by the casting number, so it is difficult to identify the heads when they are sold used.
|Cylinder Head W2||Casting Number P4532693 or 3870810|
|W5 – std chamber||P4452926|
|W5 – small chamber||P4532724|
|W7 – Sprint Car W8||P4532755 or P4532766 P4876281|
|W9 – std port||P4532847|
|W9RP – raised port||P5007904|
|Aluminum Commando – std port||P4532900|
|Aluminum Commando – large port||P4532795|
|Mopar / Brodix B1 BA MC||P5007928|
W5: A W5 head is basically a W2 made in aluminum with rectangular intake ports (instead of oval shaped W2 ports). These are designed for use on 59-degree blocks, and they use all the same component parts as the W2 (i.e., rocker arms, valves, and springs). W2 intake ports also fit the W5, except for the port shape. The W2 intakes may be ported to match the shape of the W5 with some extra work.
W7: The W7 was phased out when the W9 was launched. The two heads are interchangeable and have pretty much the same dimensions. Three versions of the W7 were made for different applications (drag racing, sprint cars, and NASCAR Craftsman Truck). The drag-racing heads have raised intake ports and may require custom fabricated intake manifolds. The sprint car heads had extra machining for the methanol injector between the exhaust side of the head and the intake ports.
Most component parts are common with the W9 heads (i.e., valves, springs, etc.).
W8: Two versions of the W8 heads were made for NHRA drag racing, and for NASCAR Craftsman Truck. The drag-racing heads have special raised intake ports. These heads are made from heavy-duty castings and feature thick wall construction for improved durability.
W8 heads are cast without much of a chamber and must be CNC machined before use. The same is true for the ports, since they are cast small and must be ported before they flow.
W8 heads require a special W8 valve cover with a wider rail and gasket than all other LA heads. These covers are pretty expensive since they are specially made for these heads. Some valve covers were cast in aluminum and some in magnesium.
Other Non-Recommended Heads
W9RP: The “RP” in the W9RP heads stands for “Raised Port” heads. These heads use a completely different casting from the standard W9. The intake and exhaust ports are raised about 5/8” more than the standard W9 heads. The raised ports improve flow, but the heads are designed for sprint cars using individual runner intake manifolds. No carburetor intake manifolds for these heads are available at this time. A fabricated intake manifold is the only way to build an engine with these heads.
The W9RP heads are sold semi finished and require extensive CNC machining on the chamber and intake ports. The ports and chamber are cast very small and don’t flow without the porting. The intake screws and rocker arms are not machined for flexibility in high-dollar racing applications. The extra work makes these heads expensive for use in most stroker engines.
P5 and P5 Hemi: The P5 and P5 Hemi® heads are for use on small-block Mopar engines but are not a wedge head. These heads are called poly-sphere heads and use a different bolt pattern on the deck. They use a different version of the R3 block that was not available in a tall deck height. These heads are also very expensive to use since a custom-fabricated intake manifold is needed, and the heads require extensive (expensive) machining and porting. The valve-gear and other component parts are also very expensive.
P7: The P7 cylinder head is another poly-sphere head that does not fit on the production or R3 blocks. These heads are currently used in NASCAR Nextel Cup, Busch, and Craftsman Truck. These heads have a unique bolt pattern and can only be used on the R5 engine block. This block is a short deck height (9.000”), so it would be difficult to build a large stroker engine with the short deck height. All component parts in the P7/R5 engine are unique and can be expensive to buy.
Recommended cylinder heads for stroker engines:
Stroker Engines from 371 to 418ci: Stroker engines from 371 to 418 inches can use stock or high-performance cylinder heads. Some port work may be needed to allow good performance as the engine gets larger. The larger 2.020” intake valves should be used in these heads. The best choices for cylinder heads with this size engine are listed below (all 18-degree heads for use with 59-degree tappet bore blocks):
Six-Bolt Heads and MLS Head Gaskets
Small-block Mopar engines have had problems with head-gasket sealing at high compression ratios ever since they were originally introduced. With only four bolts around each cylinder, this is fewer bolts than are used in most other V-8 engines. When the compression ratios get above 11:1 or higher, the head gasket is prone to leak.
In severe cases, the compression leaks into the water jacket or oil passages in the block. Sometimes this causes water to get blown out of the radiator and/or overflow bottle.
The best way to resolve this problem is to use a 48-degree R3 block and heads that have six bolts around each cylinder. The only two types of blocks with the six-bolt pattern are the R3 (48-degree versions only) and the aluminum A block. The cylinder heads that have the six-bolt pattern are the W7, W8, and W9 heads.
The 59-degree tappet bore R3 blocks don’t have the six-bolt pattern since the extra inner bolts get in the way of the pushrods. These blocks are made from the same casting, but they do not have enough material left to hold the extra bolt and fit the pushrods in at the same time.
On 59-degree blocks where the compression is lower than 11:1, standard-style composite gaskets work well. In higher-compression applications, use Cometic MLS (Multi-Layer-Steel) head gaskets.
These gaskets are multi-layer steel and have raised areas providing a good seal at high compression ratios. The outer layers are spring steel and the inner layer is galvanized steel. These gaskets work well on cast-iron or aluminum blocks and heads.
The gaskets are available in several different thicknesses, from 0.030” to 0.120”. Changing the gasket thickness is an easy way to make small changes in the compression ratio. For example, if you calculate the compression ratio at 11:1 and you want to use pump gas, you could install a thicker gasket and reduce the compression ratio by about one point or slightly more.
The deck surfaces must be clean and dry and in good condition without any nicks or scratches that could allow a leak. Don’t use oil on the threads of the head studs when using these MLS gaskets since the oil leaks down and gets the gasket wet before it can seal. Moly paste on the head studs can avoid this problem since it has a consistency like grease and won’t drip down onto the gasket-sealing surface. ARP sells a Moly-based lubricant that works well in this application.
371 to 418ci
340 or 360
Magnum R/T P5007141
LA Replacement P5007950
Large Port Commando
Brodix B1 BA
The best choice with cast-iron heads is the Magnum R/T P5007141 or the LA replacement heads P5007950. These heads flow more air out of the box and come with the valve job already done for the 2.020” intake valves. Choose the head that works best with your desired intake manifold. P5007141 uses the Magnum-style intake manifold with the vertical intake screws, and P5007950 works with LA-style intake manifolds.
Stroker Engines from 420 to 475ci: Larger stroker engines need larger intake valves and enough airflow to feed a stroker with big-block sized cubes. The heads listed below are the best choices for large stroker engines:
If you want to use cast-iron heads and plan on using a 59-degree tappet bore block, use the W2 heads P4529994, P4529995, P5007355, or P5249769. With aluminum heads and the 59-degree tappet bore block, use Brodix heads or W9 P4510324. With W2 and Brodix heads, use 2.080” intake valves. The W9 P4510324 already has the valve job done for 2.150”/1.600” valves.
Use W2 P5007445AB, P5007708AB, or W9 P5007065AB with 48-degree tappet bore blocks. Modify the W2 heads to use a larger valve size when available (i.e., 2.080”/1.600”). The recommended valve sizes for the W9 is 2.150”/1.600”. You can also use 2.180” or 2.200” intake valves, but porting is needed on the heads to use the larger valve sizes.
W2/W7/W8/W9 cylinder heads have been used extensively in racing programs. Many cylinder head porters have developed CNC programs to port these heads. The heads are ported on a computer-controlled mill that duplicates the port the same way each time.
Some of the CNC porters that have experience with Mopar heads are listed below (and in Appendix B):
- Chapman Racing Heads, Woods Cross, Utah
- Ultra Pro Machining, Charlotte, N.C.
- Weld Tech, Brownsburg, Ind.
- Indy Cylinder Heads, Indianapolis, Ind.
- Brzezinski Racing Products, Pewau-kee, Wisc.
- Hughes Engines, Washington, Ill.
The typical cost of CNC ported heads is about $1,000 per head (not counting the cost of the base un-ported head). This is expensive, but it can significantly improve the output of the engine.
If you don’t want to spend the extra money on porting heads, then select a head that flows well “as cast.” Some good choices are the Magnum R/T (229 cfm), LA replacement head (229 cfm), W2 (260 cfm), and W9 heads (300 cfm). These produce very good airflow numbers right out of the box without any porting.
Be sure to select cylinder heads that fit the block you want to use (48- or 59-degree tappet bore). The heads must work in concert with the camshaft, intake manifold, and headers to provide optimal performance. Be sure to select these parts together so that they all perform well in the same RPM range (i.e., 2,500 to 6,500 rpm for most stroker engines).
Written by Jim Szilagyi and Posted with Permission of CarTechBooks
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