Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (2023)

Cylinder heads are one of the keys to optimum performance in any stroker engine. The large displacement engine needs very good airflow over the cylinder head to produce great power. However, high flow cylinder heads only work when used with the other components designed to work together (i.e. camshaft, intake manifold and manifold).

Iron vs Aluminum

The choice between cast iron and aluminum heads is based on cost and weight. Heavy-duty iron and aluminum cylinder heads are readily available and both provide excellent performance in stroker engines.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (1)This tech tip is taken from throughout the book,HOW TO BUILD MOPAR SMALL BIG INCH BLOCKS. For a complete guide on this whole subject, see this link:


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Aluminum heads reduce engine weight by about 50 pounds. Most aluminum heads are more expensive than iron heads. Aluminum headers are also easier to repair if they crack and need welding.

Cast iron heads don't transfer as much combustion heat to the coolant, making them slightly more efficient. For this reason, aluminum cylinder head engines generally use a slightly higher compression ratio than a similar iron cylinder head engine. For example, an iron-headed engine must use a 9:1 compression ratio at the pump, while the same aluminum-headed engine can run at a 10:1 compression ratio. Combustion and heat convert fuel into mechanical energy.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (2)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (3)

valve angle

All LA and Magnum heads have an 18 degree valve angle. This valve angle is less than most other small block cylinder heads (i.e. most GM heads are 23 degrees). In general, airflow improves when the valve is raised or reaches an angle close to zero. The air-fuel mixture doesn't have to rotate as much when it enters the engine through the intake port, and this helps with flow.

Most high-performance cylinder heads for Mopar engines also use the 18-degree valve angle. The only ones with a slightly better valve angle are some versions of the W2 and all W7, W8 and W9 heads. These heads use a 15-degree valve angle to improve airflow. The 15 degree heads are also designed for use with 48 degree hole blocks. A version of the W9 and W9-RP standard (elevated connection heads) uses a 13 degree valve angle. See Chapter 3 for more information on 48 degree hole blocks.

If the valve angle is changed from the original 18 degrees, the notches in the pistons must be machined to match the valve angle. Unless the piston machining is changed, any contact of the valve to the piston will bend the valves as they will not fit in the groove. Of course, the valves should never touch the piston, but this can happen when the engine revs too much and the valve floats.

A head against a Magnum head

What are the main differences and similarities between LA and Magnum stock?


  • Same bolt pattern as cylinder head (4 bolts)
  • Same distance between valves and valve window
  • Same 18 degree valve angle
  • Same entry point (very small differences in port size and shape)
  • Same bolt pattern as exhaust flange
  • same type of spark plug
  • Equal water outlets: at each end of the camp


miI have:Omagnum
model years:1971-19921993-2002
machine size:360/3405,2L/5,9L
valve cover shapebent at the endssquare at the ends
Valve cover bolt pattern5 screws10 screws
Valve Stem Size3/8”8mm
input screw angleStandardVertical
Rocker arm/valve spring lubricationThrough block/headshollow sticks
rocker typeaxle mountedmounted screws
intake valve sizes1,880"/2,020"1,920"
exhaust valve sizes1.600”1,625"
combustion chamberOpenCerrado
combustion chamber size70cc60cc
Approximate inlet airflow160 cubic feet per minute190 cubic feet per minute
waste heat junctionhead centerednone
coolant heat transferhead centerednone
Mounting holes for accessories - headboard3 screws5 screws
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (4)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (5)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (6)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (7)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (8)


Most Mopar cylinder heads have 1.870 inches between the valve centers on each cylinder. This clearance allows for maximum valve sizes of up to approximately 2080 inches on the intake valve with 1600 inches on the exhaust valves. Any larger valve will require relocating valve guides or downsizing the intake or exhaust valve.

The W7, W8 and W9 heads have 1.936 inches of valve spacing. This extra clearance allows much more room for larger valves. It also allows for intake valves up to 2200 inches and exhaust valves up to 1600 inches. These larger valves allow for additional airflow to power a very large racing engine. Most engines over 420 cubes require large valves to allow enough airflow for good performance. Think of it this way: if your stroke engine has a large block size in cubic inches, you will need large valves (i.e. 2100" to 2200" intake valves).

ports and chambers

The most important area in any cylinder head is the intake and exhaust ports and the chamber. The shape and design of the ports control how the air/fuel mixture and combustion behave as they enter and exit the cylinder.

Most manufacturers publish port volumes to give you an idea of ​​the size of ports in stock. These data provide some information, but cross-sectional area (hole width) is also an important factor. Do not compare Mopar heads with GM or other heads by port volume as the port lengths are not the same. For example, a longer doorway has more volume, but it's not really bigger. Also remember that different Mopar heads have different port lengths and the inlet surface is not in the same place relative to the hole on all heads. Due to these changes, you cannot directly compare Mopar heads by port volume, as the port length is not always the same.


Most standard production manifolds flow between 160 and 190 cfm at the inlet port. High performance heads offer about 200-300 cfm of input flow "as is" or more with ports.

Spacing between LA and Magnum valves

Most Mopar cylinder heads have 1,870 inches between valve centerlines for each cylinder. This works well for most heads, but limits valve sizes to about 2080 inches on the inlet and 1600 inches on the outlet. To use larger valves, the valves must be further apart.

Sometimes valves with displacement valve guides can be used to allow more clearance for a larger intake valve. Often the exhaust valve is shortened to allow for a larger intake valve. These changes may help, but may cause other issues as the valve is no longer in the center of the port. Downsizing the exhaust valve can lead to a flow imbalance as the exhaust valve can become too small to balance the intake and exhaust flow.

Large displacement engines must use large valves that allow sufficient air flow for optimal performance. Any engine larger than 420cc must use 2100”, 2150”, 2180”, or 2200” intake valves and heads with large openings that allow enough airflow to support the large engine. The best options for large inch lift motors are the W9, Indy and Brodix heads.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (9)
Valve clearance per cylinder head:
cylinder headVentilabstandbigger size of intake/exhaust valve)valve clearance
puncture. Los Angeles bosses1.870"2,080" / 1,600"0,030"
puncture. magnum heads1.870"2,020" / 1,625"0,048"
aluminum magnum heads1.870"2,020" / 1,625"0,048"
R/T heads1.870"2,020" / 1,625"0,048"
W2 heads1.870"2,080" / 1,600"0,030"
W7 heads1,936"2.200" / 1.600"0,046"
W8 heads1,936"2.200" / 1.600"0,046"
W9 heads1,936"2.200" / 1.600"0,046"
edelbrock heads1.870"2,020" / 1,600"0,060"
Brodix B1BA e ESP MO1.870"2,080" / 1,600"0,030"
indian heads1.870"2,100" / 1,650"staggered guides

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (10)

The rule of thumb regarding airflow is that the engine has the potential to produce about 2 horsepower per CFM of intake airflow. The other engine components must work in harmony to achieve this result, but it gives a good idea of ​​what the possible result would be. So a 200 cfm cylinder head can generate around 400 hp and a 300 cfm cylinder head can produce around 600 hp.

The camshaft must be designed to complement the airflow performance of the cylinder heads. For example, most Magnum heads flow reasonably well up to about 0.550 inches of valve lift. The desired valve lift to work with these heads should probably be in the range of 0.475" to 0.525" to work properly with these heads. A camshaft with valves open 0.600" or more would not work well because the heads cannot flow in that elevation range.

Study the manufacturer's flow data and, if possible, consider obtaining additional data from a second, independent source. Keep in mind that not all riverbanks work the same or provide consistent data. Many riverbanks are homegrown and cannot be mapped on other riverbanks. Testing procedures sometimes differ as well, with some reporting higher numbers due to changes in procedure.

stock selection

Mopar LA headers

Specifications for these heads are listed in the table above. Detail notes and comments are listed below for each rubric. Be sure to select an axis that works with your block's ram angle. The ram angle is shown below in parentheses after each roll (in the header).

LA Production Heads - Cast Iron (59 degree blocks) - The 273 and 318 heads have very small ports and small valves. These heads do not offer much performance potential and should not be used on a stroker engine.

The 340 and 360 LA heads have larger intake ports and are the only LA heads worth using on a Stroker engine. The 340 heads have a larger 2020" inlet valve. The 360 ​​heads use the 1880" inlet valve, but can be reworked for use with 2020" valves.

LA heads cannot be used on Magnum blocks as there is no oil passage to pass the heads through the block. This oil gallery can be drilled from a magnum block, but must be done by an experienced machinist.

With a little portability, the LA heads work well in most Strocker engines up to about 418ci. The LA heads are probably the cheapest heads, but are currently only available used. Mopar used to sell these heads, but now they are sold out and cannot buy more.

W2 - Cast Iron (different versions for 48 and 59 degree blocks): W2 cylinder heads flow more air than any Mopar cast iron cylinder head (approx. 260-265 cfm at intake port). The most unique feature of the W2 heads is the oval-shaped inlet port. The intake ports are raised and must be used with special W2 intake manifolds that have oval ports. The W2's screw pattern is also further away from the ports and not the same as standard LA connectors.

(Video) Promaxx Performance Mopar Small Block Aluminum Cylinder Heads Unboxing. #NoNameNationals #Promaxx

These heads are best suited for oval track racing and drag racing. Valve timing is quite expensive as most W2 cylinder heads manufactured since 10/1/02 require T&D rocker arms. Early heads are prone to cracking if ground too finely, but changes made around 1998 added ribbing which made the heads stronger.

Commando - Aluminum (59 degree blocks): Commando heads are offered with two different port sizes. Standard port headers (P4876785) are a direct replacement for the Iron LA headers. They use the same valves, intake, rockers, valve covers and all other parts. The only change in particular is that larger oil passages need to be drilled into the underside of the rocker arm shafts. Holes should be drilled around two of the rocker arm shaft bolts for oil flow (drill to 7/16 inch diameter). These heads use 3/8" rockers and this requires rocker modification.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (11)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (12)

Large Port The Commando heads (P4876310) have a significantly larger port. Since the doors are very large, you must use W2 style rockers with more displacement to clean the entrance doors. All other components are the same as a standard LA manifold (ie valves, springs, LA intake manifold, etc.). The openings are large enough to see the pushrods in the intake bolt holes. Use some RTV on the inlet bolt threads near the inlet ports to prevent inlet bolt leaks.

Commando heads are made from the same foundry as aluminum magnums. The only difference between these heads is the machining. This common casting has a bulge or bulge at the top of the intake ports. This hub allows enough material for the Alu-Magnum rocker studs, but is not needed on the Commando heads. This extra bulge can be removed from the connection on the Commando heads (it's not necessary and it helps the air flow a bit).

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (13)

W9 - Aluminum (48 degree blocks) - W9 heads have the highest performance potential for very large stroke engines (over 420 ci). These heads have massive inlet ports that flow "like spills" at over 300 cfm. Wide valve clearance allows use of large intake valves up to 2200 inches. The exhaust port is very efficient and does not need to be larger than 1600 inches or 1625 inches even on larger displacement engines.

P5007065AB is for use with 48 degree blocks only. To allow flexibility in valve size selection, valve work is eliminated with this head. Guides are designed for 11/32" valve stems. Most engine builders use GM Manley valves that are +0.600" in length (eg Manley #11766-8 2.150" inlet and #11767-8 1.600" about to leave). The length of +0.600" indicates that the original valves (chevy small block) are 0.600" longer than the originals. The actual length of these valves is 5.540 inches at the inlet and 5.560 inches at the outlet.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (14)

The P5007065AB has a CNC machined chamber designed for use with gasoline. The chamber machining unwraps the spark plug and the spark plug machining allows the use of common 3/4 inch spark plugs.

W9 heads must be used with T&D rockers. Although expensive, these rockers are high quality parts designed for racing and HP applications. The rocker arm bolt holes go directly to the intake ports. That sounds like fun, but it doesn't damage anything, and you should use Loctite or another fuel-resistant sealant on the rocker arm bolt threads.

The valve springs on the W9 are too close to the valve cover. This means that the valve cover gasket must be trimmed to obtain spring clearance. Valve caps should also be wider than original to ensure valve spring clearance. The P4876124 valve cover kit uses sand-cast covers that have the rail rolled for extra clearance. Valve covers may have to be ground a little to get spring clearance. Custom aluminum W9 valve covers are also available from Moroso. Carbon fiber valve covers are available from Crawford & Crawford Composites.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (15)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (16)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (17)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (18)

W9 - Aluminum (59 degree block): The version of the W9 that works in 59 degree blocks is the P4510324. This rod has been modified to allow for fender spacing in a 59 degree block. This modification removes material from the outside of entry doors and limits the number of doors that can be made. This head comes with machined valves and is recommended for use with 3/8" stem valves P4876580 (inlet 2.15") and P5249886 (outlet 1.600").

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (19)

This cylinder head's combustion chamber is CNC machined to expose the spark plugs for best performance. Use spread tip spark plugs with W9 heads for best performance (eg Champion C59YC or C61YC race spark plug to add 5-10 hp).

The outer edge of the extra screws has been removed as screws cannot be used on 59 degree blocks. This will make the heads look better as the extra holes look fun without rivets or rivets.

Most versions of W9 heads use a 15 degree valve angle. Be sure to use pistons with 15 degree angled valve notches to match the valves. You can edit the pistons to change the valve angle from the default 18 degrees to 15 degrees. This machining may reduce the piston/combination compression ratio.

Replacement LA cylinder heads

You can find other sources for LA cylinder heads in the aftermarket.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (20)

Edelbrock – Aluminum (59 degree blocks): Edelbrock offers two versions of its Chrysler cylinder heads with slightly different sized combustion chambers. The Performer RPM 340 has a slightly larger chamber size. It is designed for use in high-compression 340 engines that require increased piston-to-chamber clearance. The Chrysler Performer RPM version will work on all other engines with concave or flat pistons.

These cylinder heads use special Edelbrock 11/32" poppet valves (2020" inlet valves and 1600" exhaust valves) and require special cylinder head bolts. All other original parts (ie rocker arms, valve covers and manifold) intake) can be used. Edelbrock heads cannot be used on Magnum short blocks as they use the original LA lubrication system, which requires oil passes through the block to the head.

Brodix - Aluminum (59 degree blocks): Brodix ball heads are designed primarily for oval tracks and drag racing. Two different versions are available with different inlet port sizes and different valve clearances.

B1 BA heads use standard inlets, manifolds and valve caps. Standard LA rockers can be used but require the use of special B1 rockers. GM rocker arms can also be used if the heads are lubricated via tappets and hollow rods. Custom guide plates must be made for use with GM rocker arms.

The B1 BA MC has a larger intake port and must be used with a W5 or W7 intake manifold. Exhaust manifold bolts are not machined; This is to allow for flexibility of use. An aftermarket Race Rocker Shaft Mount Kit (eg T&D) is required. Machining may be required for pushrod clearance. Valve spacing is larger than stock and can be used with 2140" intake valves and 1600" exhaust valves.

Indy - Aluminum (59 degree blocks): Indy offers two different versions of their 360 aluminum heads, these heads are the standard six head bolts with two additional head bolts per cylinder. The problem is they are designed for a 59 degree block with an 18 degree valve angle. The 59 degree blocks do not have two extra head bolts per cylinder, so the extra head bolts are not used. These manifolds come with two output bolt patterns, one for the LA and one for the W2 manifold bolt pattern.

The 360-1 has rectangular intake ports and is usually sold as a kit containing all parts between the block and carburetor. The recommended intake manifold for this head is Indy #360-R3 and is designed for use with Indy rockers with 0.800 displacement". Indy recommends this head for engines from 360 to 426 ci.

360-2 is similar, but has oval input ports. This head is also sold as a kit but can be used with an Indy or W2 intake manifold. Indy recommends this head for engines from 318 to 370 ci.

magnum heads

Magnum cylinder heads are designed for use on 1992-'98 5.2L and 1993-'03 5.9L engines. These heads can also be installed in any LA and provide an economical way to produce good performance. See the dedicated section of this chapter that explains how to install magnum heads in an LA shortblock.

Magnum cylinder heads use rocker arms mounted on bolts and require lubrication through tappets and push rods. Magnum heads use the 10-bolt valve cover. All Magnum heads except P5007950 use vertical entry screws, which is different from the side-mounted LA entry screws.

Production Magnum (59 degree blocks): The inlet port on the cast iron Magnum heads forces more air through the "cast-like-cast" ports than any other Mopar small-block production head. The intake port flows about 30 cfm more than any LA cylinder head. The exhaust port is not as good as the best LA heads.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (21)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (22)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (23)

Since the Magnum exhaust port doesn't flow as smoothly as some LA heads, the camshaft needs to add lift and duration to the exhaust for optimal performance. Increase exhaust lift by 0.010" to 0.030" and about four degrees longer (more than intake).

Stock Magnum heads are prone to cracking of the exhaust seats between the valves. Carefully check the used heads for cracks. Stock Magnum cylinder heads are no longer available new from Mopar or your Dodge/Jeep/Chrysler dealership. Most defective stocks are now replaced with Magnum R/T stock P5007140.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (24)This tech tip is taken from throughout the book,HOW TO BUILD MOPAR SMALL BIG INCH BLOCKS. For a complete guide on this whole subject, see this link:

(Video) 422 Cubic Inch Small Block Mopar. 340 stroker, Scat stroker kit, Marsh Performance Heads


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The 5.2 liter and 5.9 liter production heads are almost the same. Both use the same valve sizes and all other components. The 5.2L and 5.9L castings were made in two different foundries, so the foundry itself has some very minor differences, but nothing significant. Mopar sold both Magnums cast as parts for the 5.2L and 5.9L engines (subject to availability).

Magnum R/T (59 degree blocks): The Magnum R/T is designed as a high performance HP head for Magnum engines. R/T heads are better transported and add 20 hp and 9 lb-ft of torque to a standard engine when these heads are installed (compared to standard Magnum heads). The performance gains are even greater compared to the LA heads.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (25)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (26)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (27)

The P5007140 is fully interchangeable with all original Magnum components (ie valves, springs, brackets, guards, valve covers, etc.). P5007141 is the same except it uses a larger 2020-inch intake valve. The large valve version of this cylinder head is the best choice for most racing engines. P5007145 is the same as P5007140 (smaller valve) but comes as a complete set with valves, HP valve springs and all components.

The R/T connectors have larger terminals than the original and this leaves less room for the entry screws as they are mounted on top of the connector over the terminals. The standard rocker arm bolts are too long and drill through the intake bolt holes. A shorter 5/16" × 1.5" Class 8 bolt with spring washer must be used for the rocker arms (16 required). The original bolt can also be used if a 1/16 inch thick washer is also installed, but these bolts are not as strong as Grade 8 bolts.

LA replacement cylinder head (59 degree blocks): LA replacement cylinder heads are the same as the Big Valve Magnum R/T P5007141 except they are machined for use with an LA intake manifold. Inlet bolts are drilled to the standard LA angle and adjusted to accommodate more intakes. All other components such as valves, springs, brackets and other parts are original Magnum. The intake valve is a large 2020 inch size, use Mopar valve #P5249878.

These heads can be used on magnum blocks where a different input is desired (i.e. Edelbrock, Six-Pack, LA stock or other collectors). Due to the limited selection of Magnum sockets, this head offers the option of more options with LA sockets.

The Magnum entryway is slightly taller and narrower than an LA entryway, but both are very similar in size. Minor grinding work can be done to fit these connectors. Use an intake manifold gasket as a template to fit the connections.

These can also be used on LA blocks with tappets and pushrod oil heads. See instructions in this chapter for installing Magnum heads on an LA engine.

Magnum Aluminum (59 degree blocks): The Magnum Aluminum is an HP aluminum version of the Magnum head. Aluminum heads reduce engine weight by about 50 pounds. These heads have improved intake and exhaust ports and offer a 15-20 horsepower increase over stock production Magnum heads.

Most original Magnum components fit these heads. The only difference is the rocker studs, which are longer than 3/8" (use 3/8" - 1.75" grade 8 screws). The larger size is needed to add strength to the aluminum casting. Larger screws require toggle pins with larger 3/8" center hole (pack of 16: P4876514). The guide plates also need to be drilled to work with the larger 3/8" toggle screws.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (28)

Magnum heads with LA intake manifold

You can use a LA Y intake manifold with Magnum heads in two different ways.

The first option is to re-machine the heads to add a second set of tapped holes for intake bolts to the Magnum cylinder heads. This can be done with a grinder at an experienced mechanic.

These additional tapped holes will need to be machined with a router as they will start inside the hole for the existing vertical holes. Hughes Engines, Inc. can drill and drill your Magnum heads for LA intake manifold bolt pattern. The cost to machine these additional holes is $64.00 for each pair of heads. After this machining, the heads can be used with Magnum and LA intake manifolds. See Appendix B for the Hughes Engines address and telephone number.

Another solution to this problem is to use the new Mopar Performance Parts LA Replacement Head (P5007950). This head is a Magnum R/T head, but machined for use with LA intake manifolds (standard LA intake bolt holes only).

This head allows the use of any LA intake manifold and offers the performance characteristics of the R/T (i.e. more airflow, lighter valves, fuel efficient rocker arms, higher compression ratio, large valves and better gasket). of the lid).

This head requires the use of hollow rods and tappets that have oil passages to lubricate the top of the engine. See the section in this chapter that provides details on installing Magnum heads on LA engines.

Except for the LA intake, this cylinder head can also be used in Magnum engines without any modifications. This allows for shooting options that have never been available before (e.g. Six-Pack, Edelbrock or other special shot not available for magnum heads).

These methods can be used in racing classes that require cast iron heads and air intakes. Magnum heads offer good performance potential, but no cast iron inlets fit Magnum heads. Cast iron inlets were never made for Magnum engines, so only LA iron inlets are available. A used cast iron inlet is easy to install on Magnum heads using the two methods shown above.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (29)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (30)

Replacement Magnum heads

ProTopline Magnum (59 degree blocks): ProTopline makes the only aftermarket iron magnum head. The New Zealand-based company was in receivership due to financial problems and was out of business at the time of this writing.

Currently, the bankers who control the company are selling some of the ProTop-pline heads. Heads are cast iron replacements. These heads use all standard components.

Edelbrock Magnum (59 degree blocks): Edelbrock also offers an aluminum cylinder head for Magnum engines. These heads use 2020”/1600” valves with 11/32” valve stems. These heads feature 3/8" tilt bosses with guide plates. Larger diameter rocker studs will require rocker modifications as magnum heads typically use 5/16 inch studs/bolts.

other used heads

The following heads are no longer available new, but may be available used. Be sure to thoroughly inspect used heads for signs of damage before purchasing. The foundry numbers listed in this chapter can help identify used heads. Mopar does not sell heads by casting number in most cases, so the crosstab is required.

Installing Magnum Heads in a Short LA Block

Many people want to know how to install later Magnum heads (1992-2003) into an older LA shortblock (1967-1992). Increased airflow from Magnum heads results in power increases of 20 to 50 hp without any ports, depending on the head selected and previously used heads. The increase in intake airflow is from 20 to 60 cfm and this is what explains the significant power gains.

Some of the most common reasons are listed below:

  • Magnum heads flow more air and this generates more power.
  • LA cast iron heads are becoming increasingly difficult to find in good condition. Economical valve train options.
  • Improved cylinder head lubrication.
  • Improved valve cover sealing with 10-bolt Magnum valve covers.
  • Slight increase in compression rate.
  • Larger and lighter tubes.

These instructions apply to all Magnum axles when installed in an LA short block. Magnum stock options include: 1992-2003 production Magnum stock, aluminum Magnum stock (P4876624), Magnum R/T stock (P5007140, P5007141, P5007145) and LA aftermarket stock (P5007950).

The Magnum stocks use the same bolt pattern as the LA stocks, so they snap together quite easily. The exhaust manifold bolt pattern is also the same, making it easy to bolt the manifold and exhaust manifold. Rockers, valve covers, valves, pushrods, valve springs, retainers, valve guards and valve seals are all different, therefore Magnum parts should be used for these components.

Most Magnum cylinder heads use vertically mounted intake manifold bolts instead of the traditional bolts that go directly into the side of the head. This requires a modification to the Magnum intake manifold, which is configured for use with the vertical bolts. The only exception to this change for the P5007950 LA replacement head is that the head has been specifically machined for use with LA style (non-vertical) entry screws. If you want to use an LA manifold that you already own, or a manifold that does not fit Magnum heads, use P5007950.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (31)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (32)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (33)

The trick to installing magnum heads on an LA block is to use tappets with oil galleries and hollow rods to supply oil to the heads. AMC flat tappets (American Motors 360-401 V-8 or Jeep 4.0L I-6) are the same diameter as the LA tappets and have the necessary oil passages. These hydraulic tappets are available from Mopar as part number P4529220AB and most cam dealers and mail order. COMP Cams also sells mechanical (solid) lifts with these oil passages (part number 801-16).

(Video) How To Build A 451 Stroker Big Block Mopar! Part One: The Recipe, Assembling The Short Block

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (34)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (35)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (36)

Rods must be 5/16" in diameter to pass through the heads and must be hollow to allow oil to flow into the heads. Pushrods must be 7.625 inches long when using P4529220AB hydraulic lifters and standard Magnum rockers (which have and unmachined blocks.) This length will work with most HP hydraulic flat follower cams. These pushrods are available as Mopar part number P5007477 (set of 16).

The head gasket and magnum heads block unused oil passages that pass through the block cover. You can drill and install Allen plugs to cover these unused oil passages, but the engine will need to be completely disassembled to clean the block after drilling and threading the oil passages in the deck (see Chapter 5 for more information on covering those holes). ). ). I have built several engines without plugging these holes and have had no problems with oil leaking through the plug.

Magnums have a smaller combustion chamber (60cc for cast iron and 53cc for aluminum magnums) than LA heads, increasing the compression ratio by about a point. For most standard engines this is a performance advantage as long as the compression ratio is not too high for the pump gas. If you don't want to increase the compression ratio, use thicker head gaskets. Thicker cylinder head gaskets (up to 0.120" thick) are available from Cometic Gasket. You must use flat or recessed pistons to avoid interfering with the closed combustion chamber on magnum cylinder heads.

Recommended parts when installing Magnum heads in an LA block are listed below:

Magnum valve springs and retainers will also work, but the springs are a honeycomb design, making the retainer too small for use with HP springs. The best option is to use P5249464 and P4452032 in high power applications (see above).

Another way to save some money is to buy a set of used production Magnum cylinder heads (eg 1992-'98 5.2L or 1993-'03 5.9L). Be sure to get valve covers, rocker arms and any other reusable parts. Carefully inspect all used Magnum production heads as they are prone to cracking. The cracks are usually between the valve seats. It may be necessary to remove the valves to inspect for cracks. If the heads are broken, they are probably scrap metal as they are expensive to repair.

The cylinder head lubrication method shown above can also be used with other cylinder heads that are lubricated by tappets and push rods (ie W8, W9 and some versions of W2). These cylinder heads use different rocker arms and valve trains, so it would be best to simulate the engine and measure the exact length of the rod and order the rods according to the application.

item numberCrowdDescription
Your decision1Hydraulic flat camshaft for LA engine
P4529220ABsixteenAMC hydraulic lifts
P48760508Production Magnum Rocker (ou Prod. Magnum)
P50074771Hollow pushrod assembly - 7.625" long
P4452032sixteenHP Chrome Molybdenum Bracket
P5249464sixteenHP Valve Spring - Stroke up to 0.525"
P45292182Valve locks (or Prod. Magnum)
P52496611Valve seals (or Prod. Magnum)
P52498768Exhaust valve - 1.625 inches (Prod. Magnum)
P52498758Inlet valve - 1.92" (Prod. Magnum)
o P5249878Intake valve: 2.02" with P5007141 or P5007950 heads
P50076171Die Cast Valve Cap Kit (or Prod. Magnum)
P52496601HP valve cover gasket assembly (or Prod. Magnum)
P48767591Head Screw Kit (or Prod. Magnum)
P48760491Intake Manifold Gasket Set (or Prod. Magnum)

Heavy duty cylinder head casting numbers

The table below will help identify most HP cylinder heads by casting number. Most Mopar Performance heads are not sold by casting number, making it difficult to identify heads when sold used.

W2 cylinder headCasting number P4532693 or 3870810
W5 - Default cameraP4452926
W5 - small cameraP4532724
W7 – Coche Sprint W8P4532755 or P4532766 or P4876281
W9: default portP4532847
W9RP: elevated portP5007904
Gran R/TP5007140
The replacementP5007140
big aluminumP4532900
Aluminum control - standard connectionP4532900
Aluminum Control - Greater PortoP4532795
Mopar/Brodix B1 BA MCP5007928

W5: A W5 header is basically an aluminum W2 with rectangular input ports (instead of oval W2 ports). These are designed for use on 59 degree blocks and use the same components as the W2 (i.e. rocker arms, valves and springs). The W2 input ports are also the same as the W5 except for the port format. The W2 entries can be adapted to the shape of the W5 with a little more work.

W7 - W7 was discontinued when W9 was released. The two heads are interchangeable and have virtually the same dimensions. Three versions of the W7 were built for different applications (drag racing, racing cars and NASCAR Craftsman Truck). Drag racing heads have increased intake ports and may require custom intake manifolds. Speed ​​car heads had additional machining for the methanol injector between the exhaust side of the head and the intake ports.

Most of the components are the same in 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. Drag racing heads have special raised entry ports. These heads are made from heavy-duty cast iron and feature heavy-duty wall construction for durability.

W8 heads are cast without many chambers and must be CNC machined before use. Same goes for ports as they are small and need to be ported before flowing.

W8 heads require a special W8 valve cover with a wider rail and gasket than all other LA heads. These covers are very expensive as they are made specifically for these heads. Some valve covers were cast in aluminum and others in magnesium.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (37)
Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (38)

Other heads not recommended

W9RP: The "RP" on the W9RP heads stands for Raised Port heads. These heads use a completely different mold than the standard W9. The intake and exhaust ports are raised approximately 5/8" above standard W9 heads. The raised ports improve flow, but the heads are designed for Sprint cars that use single port intake manifolds. Currently there are no carbureted manifolds for these cylinder heads. The built-in intake manifold is the only way to build an engine with these cylinder heads.

W9RP heads are sold semi-finished and require extensive CNC machining of the cam and inlet ports. The ports and camera are very small and will not flow without the ports. Inlet bolts and rocker arms are not machined for flexibility in high-end racing applications. The extra work makes these heads expensive to use on most racing engines.

P5 and P5 Hemi: The P5 and P5 Hemi® cylinder heads are used on small block Mopar engines, but are not wedge cylinder heads. These heads are called Polysphere heads and use a different screw pattern on the deck. They use a different version of the R3 block which was not available for high deck heights. These manifolds are also very expensive to run due to the need for a custom manufactured intake manifold and the heads requiring extensive (expensive) machining and portability. The valve mechanism and other components are also very expensive.

Q7: P7 stock is another polysphere stock that does not fit production or R3 blocks. These heads are currently used on the 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 has a short deck height (9,000 inches), so building a large racing engine with a short deck height would be difficult. All P7/R5 engine components are unique and can be expensive to purchase.

General recommendations

Recommended cylinder heads for Stroker engines:

371 to 418 cuin lift engines: 371 to 418 inch lift engines can use standard or heavy duty cylinder heads. Some port work may be needed to allow for good performance as the engine grows. Inlet valves larger than 2020 inches must be used with these heads. The best options for heads with this engine size are listed below (all 18 degree heads for use with 59 degree tappet blocks):

MLS six bolt heads and cylinder head gaskets

Small block Mopar engines had head gasket sealing issues at high compression ratios from the start. With only four bolts on each cylinder, that's fewer bolts than most other V-8 engines. When compression ratios exceed 11:1 or more, the head gasket tends to leak.

In severe cases, compression occurs in the water jacket or oil passages in the block. This sometimes results in water leaking from the radiator and/or the overflow bottle.

The best way to solve this problem is to use a 48 degree R3 block and six bolt heads around each cylinder. The only two types of blocks with the six-hole pattern are the R3 (48 degree versions only) and the aluminum A-block. Cylinder heads with six bolt patterns are the W7, W8 and W9 cylinder heads.

The 59 degree pushrod bore R3 blocks do not have the six bolt pattern because the extra internal bolts get in the way of the pushrods. These blocks are made from the same casting, but no longer have enough material to hold the extra bolt while also mounting the pushrods.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (39)

On 59 degree blocks where compression is less than 11:1, standard style composite gaskets work well. For high compression applications, use Cometic MLS (Multi-Layer-Steel) head gaskets.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (40)

These gaskets are made of multilayer steel and have raised areas that provide a good seal at high compression ratios. The outer layers are made of spring steel and the inner layer is made of galvanized steel. These seals work well with cast iron or aluminum blocks and heads.

Gaskets are available in a variety of thicknesses from 0.030" to 0.120". Changing the gasket thickness is an easy way to make small changes to the compression ratio. For example, if you calculate the compression ratio as 11:1 and want to use a gas pump, you can install a thicker gasket and reduce the compression ratio by about a notch or so.

Roofing surfaces must be clean, dry and in good condition, with no nicks or scratches that could allow leakage. Do not use oil on the cylinder head stud threads when using these MLS gaskets, as the oil will penetrate and wet the gasket before it can seal. Molybdenum paste on the head bolts can prevent this problem as it has a greasy consistency and does not run on the gasket sealing surface. ARP sells a molybdenum-based lubricant that works well for this application.

(Video) 3 Common Head Gasket Mistakes Made by Mopar Engine Builders(that Affect All Brands)

machine size

371 e 418ci

cast iron

340 or 360

production magnum

Magnum R/T P5007141

Replacement LA P5007950




Great Port Command


With 360-1

Brodix B1BA

The best option with cast iron heads is the Magnum R/T P5007141 or LA replacement heads P5007950. These heads pull more air out of the box and come with the valve work already done for the 2020 intake valves. Choose the head that best fits your desired intake manifold. The P5007141 uses the Magnum style intake manifold with the vertical intake bolts and the P5007950 works with the LA style intake manifolds.

420 to 475 Stroke Engines: Longer stroke engines require larger intake valves and sufficient airflow to service a stroke with large block size hubs. The cylinder heads listed below are the best options for long stroke engines:

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (41)

If you want to use cast iron heads and want to use a block with a 59 degree hole, use P4529994, P4529995, P5007355, or P5249769-W2 heads. For aluminum heads and 59 degree bore block, use P4510324 Brodix or W9 heads. Use 2080" intake valves on W2 and Brodix heads. The W9 P4510324 has already done valve work for 2150"/1600" valves.

Use W2 P5007445AB, P5007708AB or W9 P5007065AB with 48 degree drill blocks. Modify W2 heads to use a larger valve size if available (eg 2080"/1600"). Recommended valve sizes for the W9 are 2150”/1600”. You can also use 2180" or 2200" inlet valves, but head connections are required to use larger size valves.

CNC doors

W2/W7/W8/W9 cylinder heads were widely used in racing programs. Many bearing carriers have developed CNC programs to carry these bearings. The heads are ported in a computer-controlled mill that duplicates the port the same way every time.

Some of the CNC loaders that have experience with Mopar heads are listed below (and in Appendix B):

  • Chapman Racing Heads, Woods Cross, Utah
  • Ultra Pro Machining, Charlotte, North Carolina
  • Welding Engineering, Brownsburg, Indiana.
  • Indy cylinder heads, Indianapolis, Indiana.
  • Brzezinski Racing Products, Pewau-kee, Wisc.
  • Hughes Engines, Washington, IL.

The typical cost of CNC port heads is about $1000 per head (not including the cost of the unported single head). This is expensive, but it can greatly improve engine performance.

If you don't want to spend the extra money shipping heads, choose a head that flows well "as is". Some good options are the Magnum R/T (229 cfm), LA (229 cfm), W2 (260 cfm) and W9 (300 cfm) heads. These generate very good airflow numbers directly without connections.

Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (42)


Be sure to select materials that match the block you intend to use (48 or 59 degree plunger bore). The heads must work together with the camshaft, intake manifold and heads for optimal performance. Be sure to select these parts together so they will work well in the same RPM range (i.e. 2500 to 6500 RPM for most stroke engines).

Written by Jim Szilagyi and published with permission from CarTechBooks


Best Mopar Small Block Stroker Cylinder Head Guide - Mopar DiY (43)

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2. Mopar 906 440heads ported
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3. Corrections, Updates And Small Block MOPAR Head Review
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4. Small Block Mopar: Quick Guide to Head Porting.(Hayden's Heads)
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