Читать книгу Mopar Small-Blocks - Larry Shepard - Страница 7
ОглавлениеThe engine’s cylinder block is the basic foundation for virtually everything in an engine project, and as such, it affects almost every part in the engine, either directly or indirectly. Improved performance is the typical goal of an engine project, and to accomplish this basic goal, all parts used in the engine must work together.
All parts need to be compatible, but they should also be complementary. You may take the engine apart and put it back together several times before you arrive at the final assembly steps to complete the engine. As you begin building your foundation, use a notebook to keep track of everything that you see and do, from casting numbers to bore sizes, etc., for every part that you use. Once the engine is together, it can be very difficult to gain this information and it may be helpful for any troubleshooting that is required.
Basic block design could be considered similar to architecture because it defines how the block is laid out. An engine family such as the LA-engine and the Magnum extension tend to share many features that define them. The LA-engine small-block family is a basic 90-degree V-8. This angle is best for dynamic balance considerations and also makes for a very rigid block.
Once the block is disassembled or the new block is obtained, it is usually mounted to the engine stand. It is typically mounted upside down or crank-side up because that section is where you are going to start.
The bare block, no plugs, is the first step in preparation for sending the block to the machine shop. In this common position, the block is upside down and the passenger’s side is toward the left, which can be confusing. If this were a Chrysler race block (cast-iron versions), the large “X” or “R” would be located on the passenger-side face of the block, which is also the passenger-side face as installed in the car. It is on the front of the number-2 cylinder, above the dipstick holes and the core plug.
Both A-engine and Magnum blocks share the same 10-bolt head bolt pattern, or 4 bolts around each cylinder, but some of the race blocks add 2 more (for a total of 6) per cylinder, and this is covered later in this chapter.
Cylinder numbering begins with the driver-side front cylinder; number-2 is the passenger-side front cylinder. The A-engine has a production deck height of 9.60 inches; the Magnum group uses 9.585 inches. Small-block race blocks have deck heights as low as 9.0 inches. Both groups of small-blocks share the 4.46-inch cylinder bore centers and the 6.125-inch camshaft centerline height. The LA-engine block is lighter than the original A-engine block and weighs about 160 pounds. The newer 1973–1974 thinwall cast versions are about 4 to 8 pounds lighter, which carries over to the Magnum blocks.
Although there are four different cylinder bore sizes, Chrysler made two basic blocks. One is the 273, 318, and 5.2L block; the other is the 340, 360, and 5.9L block. Most A-engines use a motor-mount design that attaches to the sides of the block close to the front, and the mount ears and bolts are parallel to the cam centerline. The 273 and 318 share the same arrangement.
However, the 340 and 360 share the same driver’s side configuration, but the passenger’s side has the three-bolt pattern reversed.
The Magnum engine, originally used in trucks, had a three-bolt pattern on each side, and these mounts bolted into the side of the block itself. This bolt pattern is located in the center of the block starting just above the pan rail. In addition, these Magnum blocks had the ears cast in and machined for the earlier system.
Both groups of blocks have three core plugs per side; the 318 group has them wide-spaced, and the 340–360 group has each core plug aligned with the center of the water jacket between two cylinders.
The easiest way to identify a small-block Mopar is to compare the casting numbers. Each casting is unique. In other words, you can’t machine out the 273 bores to make a 318. You also can’t make a 340 out of a 318.
These rules don’t apply to 340 and 360 blocks. You could probably bore out the 360 block to the 340 stock bore size of 4.04 inches, but the 360 has a large main bearing diameter crank. The large main bearing diameter makes the long-stroke 360 (3.58 inches) much stiffer. In addition, the 340 oil pan’s front and rear sealing surfaces are the same as the 318’s; the 360’s are smaller.
The 1970 340 T/A is the trick block for racing applications because it has thick bulkheads on the number-2, -3, and -4 main bearing bulkheads. The added thickness allows for vertical four-bolt main caps to be added to these center mains. None of the Magnum blocks have this thick bulkhead. In the mid-1970s, Chrysler offered a four-bolt main race block known as the X-block (it had a large “X” on the passenger-side front wall of the casting). In the mid-1990s, Mopar Performance and Chrysler revised this race block and offered the R1 through R4 race blocks. These were generally called the R-blocks and all featured four-bolt mains.
When you are selecting a block for your particular build, remember that for all five of my performance packages, the standard 340/360 or Magnum block can be used as long as the bore size is limited to .020/.030 overbore for the last two packages. An R-block is not required as long as the blocks are limited in overbore. If a big-bore engine is desired, an R-block is required, and the siamesed-bore version allows the largest bores. The 340 resto block is a version of the R-block. If your 340 or 360 block is already overbored too far, sleeve the bore back to 4.020 inches (360) or 4.04 inches (340).
The 340 T/A block is very difficult to find; it’s even more difficult to find someone willing to give one up for a performance project. The 340 resto block, by Mopar Performance, is more readily available. It uses the 340 T/A casting number and the 340 displacement number after it, followed by an “M,” all the way to the right after “340.”
The 318/5.2L and the 360/5.9L are the two groups of small-blocks. You can identify them easily by quickly looking at the core plugs located in the sides of the blocks. There are three in each side. In the 340 and 360/5.9L group, the core plugs line up with the three center bulkheads, and if the plugs are removed, you can see the water-jacket gap between adjacent cylinders.
On the 318 and 5.2L blocks, the core plugs are spaced farther apart and don’t line up with the bulkheads, except the center one is close to the number-3 main. The R-block will support the most power, then the X-blocks and then the T/A and then all stock blocks. Magnum blocks are slightly stronger than the standard A-engine blocks. The stock blocks with 0 to .020/.030 overbore have done over 550 with no problem (good bolts and good main caps) but the upper limit is unknown. Most members of the 700-hp club use some version of the race block. The race blocks make more horsepower.
Around 2000, Mopar Performance started offering a 340 restoration block that not only had the thick bulkheads of the 1970 T/A block, but also had actual four-bolt mains on the center three mains. It used the same casting number as the original 340 T/A with a 340-M added, but the siamesed-bore block is no longer offered. This stout non-siamesed bore block can support at least 1,000 hp, but availability is limited. The R3 race block is an excellent block for 700-hp street builds, but these can be expensive and difficult to obtain so other choices are offered.
The large round hole with a plug in the center is the cam’s rear plug. The threaded square-drive plugs on either side of the cam plug are the oil galley plugs. These allow the oil galleys to be drilled and then sealed. The main oil feed galley is the one on the right.
The 318 Magnum block is tipped over to the driver’s side so the passenger-side deck is horizontal. The oil galley plugs are in the middle toward the bottom. The distributor bore is at the left and the china wall runs up toward the right from the large distributor bore. The rear intake gasket seal is just ahead of this surface. At the upper end of this machined surface is another oil hole typically used for oil pressure senders. It is important to know where this hole is for future discussions in this chapter.
The bare front face of the block has lots of holes. The core plugs are the two at the bottom; one is on the right while the other is on the left. At the top right and left are the block’s two water feed holes. The cam bore is in the center. The oil galley holes are on each side of the cam bore. The cam retainer is attached by the four smaller holes: two below and two above. The two larger holes above the cam retainer attaching bolt holes are vents from the tappet chamber to the front cover.
With the main bearing shell removed, you can see the two oil passages intersect just above the hole. The white welding rod is in the main oil feed from the main oil galley (hole to the right of the cam plug hole). The oil comes from the main oil galley down to the main bearings and then up to the camshaft through this Junction.
Race Blocks
The original race block for Mopar small-blocks was the 340 T/A in 1970. It was produced for only one year. When NASCAR began handicapping the big-blocks, both Hemi-head and wedge-head designs in the early 1970s, the NASCAR teams began using the T/A blocks, but they had to remove them from actual Trans-Am cars. This was a lot of extra work! To solve this problem, Chrysler introduced the X-block, which had all the features of the T/A block plus a few more. This X-block was readily available to racers and was very successful.
When the government issued the loan guarantee to keep Chrysler operating, the X-block tooling was lost during the confusion it created. In the late 1980s, the demand for a race block began to build, so Mopar Performance introduced the new “R1” block, which replaced the X-block. Then came the R2, R3, and R4. Each one has its name cast into the passenger-side front wall of the block.
Block Height Calculation
The block height, or deck height, is defined as the distance from the center of the crankshaft to the top of the block’s deck surface, measured along the cylinder bore’s centerline. The small-block Mopar’s production block height is 9.58 to 9.60 inches, but blocks are commonly milled or decked at each rebuild, so do not depend on this number as an absolute. You don’t always know the block’s history. However, you can calculate the block height using the following simple equation:
BH = S ÷ 2 + RL + CH + DH
Where:
BH = block height
S = stroke
RL = rod length, center to center
CH = compression height of piston, measured on the actual piston
DH = deck height of piston, measured in the actual block
For example, on a 318 (or 5.2L) engine, the stroke is 3.31 inches, rod length is 6.123 inches, stock piston’s compression height is 1.74 inches, and the piston’s deck height is .082 inch below the deck. Using the formula, you find that block height is 9.6 inches (1.655 + 6.123 + 1.74 + .082).
If this engine’s deck height measures .062 inch (instead of .082 inch), it indicates that the block has been decked .020 inch.
Deck height is often confusing because it sounds similar to block height. However, it is defined as the distance from the top (flat) of the piston at top dead center (TDC) to the top of the block’s deck surface. Typically, it is measured with a dial indicator or a bridge, which includes a dial indicator. If you have a dished or domed piston, the top of the piston is the flat part at the outside edge that is not part of the dome or dish.
This drawing shows the relationship of the various block specs required for the block height calculation. The key spec is the piston’s deck height because it is used in the compression ratio calculation, which is very important for max-performance engines.
The standard production small-block tappet angle is 59 degrees (shown), but the R-block family has the capability for using 48-degree tappets. The 48-degree angle was selected based on installing a race W cylinder head and race adjustable rocker arm onto the block (in the computer) and drawing a straight line from the center of the camshaft to the center of the rocker’s pushrod pivot. The resulting tappet angle was 48 degrees. While the R-block casting is made to use both the tappet angles, once the block is machined for one tappet angle, it can’t be converted to the other tappet angle!
Some of these R-blocks are cast with siamesed-bores, which means that the bore walls of adjoining cylinder bores are merged together, with no gap. This siamesed situation exists at three places per side (cylinder bank). This siamesed-bore alignment generally allows the actual cylinder bores to be larger because there is no water-jacket between the cylinders.
R-blocks can be converted to a six-bolt cylinder head by adding two more head bolts to the stock four-bolt pattern. This is a critical upgrade for super-high compression ratios, such as 13:1. A study showed that four-bolt heads were bending the head over the gasket’s sealing ring. The two extra head bolts keep the gasket material farther away from the bore. The bolts and gasket support help maintain a flat deck surface with high clamping loads.
The 59-degree tappets are so close to the tappet wall that the wall has a relief machined in for each tappet/pushrod on the Magnum blocks. The 48-degree tappet blocks have the tappet bosses much farther away from the tappet wall with no reliefs required.
Magnum tappet bores are machined at the top to provide space for the yoke to sit around the hydraulic roller tappets. The yoke sits in the relief and is held in place by the spider.
One boss was added straight up in the tappet chamber and one was added straight down on the outside of the block. In some cases these bosses are left unmachined or are machined off if not desired. If they are machined, they do not have to be used. If you use them, you must use a six-bolt–style head gasket. All of these race blocks (X and R versions) are cast-iron blocks made with high-nickel-alloy cast iron.
Most LA-engine small-blocks were built at the Mound Road Engine plant in Detroit, then added to the Windsor engine plant in Canada, and later the Toluca plant in Mexico. Many A-engine blocks were cast at Chrysler’s Indianapolis, Indiana, foundry, which was closely involved in the early stages of the R-family of blocks.
Aluminum Blocks
Mopar Performance began offering aluminum small-blocks designed for racing in the early 1990s. They are designed and built for the serious Sprint Car and drag racer who competes in classes that allow aluminum blocks. The latest version weighs approximately 95 to 100 pounds, a weight savings of more than 25 pounds over the previous version. These blocks were offered in two basic deck heights, 9.00/9.10 and 9.56 inches. They are shipped with one of several options in bore size.
The Mopar aluminum small-block shown comes in basic deck heights: stock-style height of 9.56 inches and the short-deck version at 9.00 inches; it can support more than 1,000 hp. The block features a fully skirted low end, similar to the 426 Hemi.
Only two core plugs are installed per side in the aluminum block. There is also one large one in the front face. Notice that the center three mains are cross-bolted for maximum strength, similar to the 426 Hemi. Each center cap (number-2, -3, and -4) is cross-bolted similar to the 426 Hemi in Top Fuel. Therefore, it’s much stronger and stiffer than any four-bolt cap, but the cast-iron blocks do not have the skirt on the block for anchoring.
The aluminum block uses steel main caps, and the center three are cross-bolted. Moreover, they use studs rather than bolts for greater strength. The unique front cover does not match the A-engine or Magnum engines.
By about 2005, Mopar Performance offered more than 20 different blocks for the small-block. All were designed for racing; many options were available for virtually any engine project.
The deck surface shows the sleeves pressed in each cylinder. The standard four-bolt small-block head bolt pattern sits around each bore with the added top and bottom bolts showing the six-bolt race pattern. The four-bolt head gaskets and four-bolt head works without the two extra bolts if that is desired. Note how far the tappet bores (48 degree) are from the centerline of the cylinders, even with the six-bolt in the tappet chamber.
The aluminum block does not use either style of motor mounts and is designed for use with motor plates. The block is much lighter without all the motor-mount bosses.
Mopar Performance Aluminum Block Features
• Ductile iron dry cylinder liners
• 48-degree tappet angle for almost ideal valvetrain geometry
• Six-bolt head bolt pattern for superior head gasket sealing
• Full skirted block design, similar to 426 Hemi for increased strength and rigidity
• Cross-bolted main caps for added strength
• High-strength A1 studs, bolts, etc.
• 50-mm roller cam bearings designed to reduce friction
A new block will come with new cam bearings but all others will have to have the cam bearings replaced. The block is upside down and the cam bearing oil hole is shown at the top and points down toward the main bearings. The oil holes in the bearing shell must line up with the holes machined into the block. In some cases you must use a small mirror to see if this is true.
The standard water jacket extends down to just above the block’s pan rail. The core plugs are at the bottom of the water jacket. a threaded plug is also there that allows draining of the block. These threaded plugs are difficult to use after time. Installing a block drain allows you to drain the block fully and easily.
Bore
The amount of overbore depends on the block itself and when the block was built. Early 273 and 318 blocks (pre-1973–1974) can generally be overbored about .060 inch. Early 340 blocks can be overbored about .040 inch, or 4.080-inch actual bore size. The 360 is a gray area, but I use the 340 as a guide and limit overbore to .040 inch, or an actual bore size of 4.04 inches. All newer blocks, A-engines, and Magnums are thinwall casting designs, and overbore should be limited to .020 to .030 inch.
All race blocks can be overbored more than production blocks. You can overbore the resto block to 4.08 inches with the siamesed-bore versions able to be overbored the most (approximately 4.22-inch max for the siamesed-bore versions). When pushing the boundary of bore size and overboring, it is best to sonic-test the block before you begin any boring operation.
The main bulkheads must have enough material and strength to support four-bolt caps with vertical outers. Thus, there must be enough material between the main cap bolt of the two-bolt design and the outer wall below the pan rail. In this drawing, the dotted line represents the standard block casting. The solid line above it is closer to the performance blocks, such as the 340 T/A and the X and R block families. The vertical outer bolts break through in the standard casting. The main reason for splayed outer bolts is to put the bolt into solid material. This drawing is not to scale.
Most race blocks are bored or rough bored to approximately 4.00 inches. There are many reasons to use a race block even if the bore size is less than 4.00 inches (such as the 318’s 3.91 inches). If you plan to race a small-bore engine, such as 3.91 inches or even 3.63 inches, you should not use the production block. It is a better package to use the race block with the proper-size sleeves.
Mains
The two basic main sizes are the 273/318/340 and 5.2L engines. The 360 and 5.9L use a larger main. The 360 has a large 3.00-inch main; the other group is small at 2.69 inches. The main cap bolt spacing on the 360/5.9L is also wider, or spread. Magnum engines have a small dowel that locates the number-5 main cap. Magnums also use smaller main cap bolts in the number-5 cap. Typically the main caps are made of high-nickel cast iron. If the main caps have been replaced or damaged, or if they bind during crank rotation, the mains should be align-bored, which is a machine shop operation.
Height
Most A-engine blocks were built at 9.60-inch block height; Magnum engines were built at 9.58 inches. Race blocks can be about 9.00- to 9.10-inch block height. Do not try to mill a production block to this height. Deck milling on production blocks should be limited to about .060 inch.
You need to determine if the engine was rebuilt or repaired in the past and whether the block was decked .060 inch at that time. If the block has been decked by .060, the actual deck now is 9.54 inches. You should not take off another .060 inch because the deck becomes too thin and causes head gasket sealing problems that you will not be able to fix. This is one reason that it is so important to measure the block’s actual height before you start machining.
Stroke
The A-engine/Magnum engine can generally accept long-stroke cranks. Most of them use a 3.31-inch stroke; the 360/5.9L uses a longer 3.58-inch stroke. The performance aftermarket offers 4.00-inch strokes that are easy fits. Because the camshaft sits so high above the crank, long-strokes do not cause the connecting rods to hit the camshaft lobes. The pan rail and the bottom of the cylinder bore (pulling the skirt too far out the bottom) are still concerns with strokes longer than 4.00 inches.
Oil routes from the pump to the oil filter on the side of the block, and then back into the block and up to the right side (next to cylinders-2, -4, -6, and -8) main oil feed galley. The right oil galley runs from the rear of the engine to the front, and it feeds down to the main bearings. As can be seen, the tappets are oiled directly since the tappet bores intersect with the galley. Then the oil goes up to the cam bearings.
A-engine and Magnum blocks oil in basically the same way. The difference comes in oiling the head and valvetrain. The A-engine oils the valvetrain and head through the head; Magnum engines oil the valvetrain and head through the pushrods.
Basically, the oil pump feeds the oil filter and then pushes oil to the passenger-side main oil galley. From the main oil galley, the oil feeds the passenger-side tappets and the main bearings. Then it crosses to the driver-side oil galley and oils the driver-side tappets. Then, from the mains, the oil goes to the camshaft bearing.
On the A-engine, the oil goes to the rockers and the head from the cam bearing and through passages in the block and head to the rocker shaft. On Magnum engines, the oil goes to the head and rockers through the pushrods from each tappet.
Block Plug Verification
All A-engine and Magnum blocks have a special plug at the rear of the block pressed into a vertical passage in the block. The first priority is to check that it is there. The second priority is to see if it is properly installed because it is vital to the proper function of the oiling system.
All small-blocks use a small, pressed-in plug at the rear of the block. This plug is not visible once it is installed. It is installed in a vertically drilled passage and divides the oil passages into “to-oil-filter” and “from-oil-filter” sections; both are drilled horizontally inward from the oil filter mounting area. This plug should sit at 7½ inches to 7 below the rear china wall and 2⅛ to 2⅜ inches above the parting line for the number-5 cap. If the plug is too low, use a flat dowel to tap upward into position.
The special plug is very important to the engine’s oiling system. It blocks the oil from the oil pump from going straight up and forces it to go out to the oil filter. Once it passes through the filter it returns to the block above the plug and goes directly to the main oil galley. If the plug is missing or not installed properly, it could cause erratic, low, or no oil pressure.
With the main cap off, you can check the height of the special oiling plug, which is pressed up inside the passage covered by the number-5 cap; a white welding rod can be used to measure. The correct height should be 2⅛ to 2⅜ inches.
The aftermarket (specifically Schumacher Creative Services) makes mounts/brackets to use with either the 340/360 or 273/318 ears. Race blocks use the 340–360 ears but are often machined off to lighten the engine. Aluminum blocks are designed for mounting by motor plates.
The backsides of the motor mount ears are machined to hold tolerance on mount location and thicknesses. The three ears form a sort of box with one corner missing. The change from 340/360 to 318/273 on one side is that the missing corner ear switches location, so the mounts are not interchangeable. The aftermarket mounts (from Schumacher) make a full box bracket and include all four holes to fit either engine.
Magnum blocks may have both styles as shown. This Magnum block (5.2L) has the four ears, machined on the rear, and the bolts into the side of the block (only two are showing) so it could be used with either style of mount.
The Magnum engine uses bolts (three per side) directly into bosses in the middle of each side of the block. The three bolts are spaced around the right core plug: one to the bottom, one to the upper left, and one to the upper right, both just below the pan rail. Remember, the block is upside down.
Core shift occurs when a core such as the water-jacket core moves or shifts relative to the cylinder bores or if the core breaks, which allows the ends to shift. If the core shifts, thin sections will be on one side of the bore and thick sections will be on other sides of the bore. Remember that the core is a solid piece so if it shifted, then all sides will be shifted in the same direction. For example, if cylinder number-1 has the core shifted upward and cylinder number-3 has it shifted downward, then it probably isn’t a core shift!
Cores are used to make all cast parts, including cylinder blocks. A core is typically made of hardened sand and is used to make an internal passage or relief such as the water jacket. A special bonding agent holds together the hard sand. Cores don’t typically bend but they do break. And when cores break, the broken pieces usually tear large holes and/or create solid chunks where they aren’t supposed to be, and then the block has to be scrapped.
All production small-block engines use the same ten-bolt-per-bank head bolt pattern, which is four bolts around each chamber for exceptional clamping strength. Some race blocks use the eighteen-bolt-per-bank head bolt pattern, which has six bolts around each chamber. If you have a six-bolt race block and your application does not require the two extra head bolts, you can use four-bolt heads and four-bolt gaskets and not install bolts on the two extra holes per cylinder. All high-performance packages that I put together use 11.5 CR max, and the current MLS gaskets from Fel-Pro or Cometic will easily seal this with the standard four-bolt system. The six-bolt system is not required for street/strip.
Although the Magnum group and A-engine water pumps look similar when installed on the engine, they are not because the Magnum group does not have an attachment hole in the right side of the cover for the mechanical fuel pump (all MPI) and the A-engine cover has a hole with two attaching bolts for the mechanical pump. In addition, the two water pumps run in opposite directions and the vanes that direct the water into the pump that are cast into the cover are tipped in opposite directions.
Once you decide to deck the block, be sure to address the head dowel pins, two per bank. They are pressed into the deck surface and must be removed before the milling machine can deck the block. They should be installed after the milling is complete. I recommend new ones. If they are being replaced, check the height before removing and set the new ones to the same height.
All Magnum engines have a two-bolt crank sensor mount at the right rear of the block next to the bellhousing face. The bosses are machined for a two-bolt attachment and the sensor itself can look directly at the ring gear wheel. This sensor would not be used if you do not use fuel injection (MPI) but is mandatory if you plan on using Multi-Point Injection. If you want to add the Magnum-style fuel injection to an A-engine, consider duplicating this boss, location, and basic setup.
The 48-degree tappets were created to offer the perfect valvetrain. The race blocks can be machined with either the standard 59-degree tappets or the 48-degree tappets. Once machined, they can’t be changed. Similar to the 50- and 60-mm cam bearings, the biggest advantage for the 48-degree tappets comes about with high cam lifts, high valvespring loads, and high engine RPM.
Today, block castings are machined on CNC-machines, and this precision machining process centers the actual machining on the cylinder bore and centers the wall thickness. This centering process tends to reduce or cancel out the effects of any core shift. In addition, foundries today try to design the cores so that they are locked in place and can’t move once assembled. The foundry uses sonic testing to help find any broken or damaged core blocks and keep them from getting into the machining process.
Find a machine shop that has a history of machining Mopar engines and that engine builders recommend highly. As such, a machine shop familiar with the A-engine small-block design will perform the best job. This basic process actually starts with a close inspection followed by many accurate measurements. The measuring process usually starts with a thorough cleaning of the various parts. With new parts you tend to know more about them when you bring them to the machine shop; in some cases you may have purchased them already machined. Race blocks are often shipped rough-bored so your machine shop can finish them to your specifications.
You can make many measurements on the block, such as bore size (diameter in inches) or center-to-center distance (4.46 inches on small-blocks) and many others. The dial vernier is the quick and easy way to get rough ideas of what you are dealing with. The machine shop will use a dial bore gauge for the fine-tuning measurements. This is usually the preliminary step to boring/honing the block.
The honing stones work on the cylinder wall, and the result is a crosshatch and roughness in the finish. The typical cross-hatch angle is about 45 degrees. The roughness you could describe as very smooth, but you generally do not want to mirror finish.
Honing Plates
Honing locations for A-engine and Magnum engines are reasonably common. A honing plate is a 1- to 2-inch-thick steel or cast-iron flat plate with all head bolt holes and cylinder bores. The heavy plate attaches to the cylinder block and uses the actual head bolts, which are torqued to the same specifications as the heads.
A honing plate is designed to simulate the stresses, distortions, and wall movements that are normally caused by the installed and fully torqued cylinder head.
It is generally recommended that the main caps be installed and properly torqued during this honing operation.
The machine shop tends to have the honing plate and will have the special head bolts to attach it with. To do the best job, the thread engagement with the honing plate should match the thread engagement used for the cylinder head. (Photo Courtesy R. Koffel)
Honing plates should always be used when boring and honing the cylinder block. These put the cylinder head stresses into the cylinders, so that it simulates what the cylinder walls do with the head installed. During this process the cylinder bore’s diameter is measured with a dial-bore gauge. The machine shop leaves about .001 to .002 inch of material for the final honing operation.
Decking/Milling
Once cleaned, the machine shop can tell how flat the deck surface is and if there is any damage (scratches, etc.) that needs to be fixed. You probably don’t need to deck a new block. The decking process tends to remove .010 to .020 inch, unless a special amount is requested. Typically, production blocks can have up to .060 inch milled off without causing problems.
With a new block, you select the bore size based on the block’s overbore capability, but you typically leave yourself room for at least one rebuild. With a used block, once cleaned and measured, the machine shop gives you some numbers: what is takes to fix the wear that is observed, which will be something around .010 to .020 inch (and you know the maximum the block should be overbored); on today’s thinwall blocks, the overbore number is about .020 to .030 inch. Older blocks (1972 or earlier) can do .040 to .060 inch, but the old 340 blocks should still be limited to 4.08-inch max!
Milling Calculation
Precisely fitting all engine parts together requires extremely accurate machining. When you mill or deck any part of the engine (with the most important being the block and head), consider milling all three surfaces so everything lines up again as the engineers planned. It is too late when you find that the manifold does not fit to the head at final assembly. This is not just a concern for the block. Take the amount that you plan to machine off the block’s deck surface and add that to the amount that you plan to machine off the head’s deck surface.
For example, if you take .030 inch off the head and .020 inch off the block, it makes a total of .050 inch. The intake manifold face cut could be made to the intake manifold, but I recommend that it be done to the intake face on the head. That way all manifolds fit, rather than having to specially machine all manifolds for this engine. If the china wall front and rear aren’t shorted the proper amount, they tend to hold the intake manifold up, and it won’t seal to the head. This is probably not required for small amounts such as .010 inch.
You can assume that new heads are machined to fit like a production head with zero milling. New heads might be milled to change the combustion chambers to a specific size.
Align-Boring
Sometimes a used block has distorted or damaged main bearing caps and saddles. If you’ve measured the caps and saddles and determined that they need honing or boring, a machine shop needs to perform this service. Align-boring trues them so the crankshaft performs at its best and does not bind.
Align-boring is required if the block’s main caps have been replaced (one or all), and upgrading to steel main caps provides additional strength. To align-bore the block, a very small amount of material is removed (milled) from the main cap’s parting line surface of each main cap. (Photo Courtesy R. Koffel)
Stress Relieving
Manufacturers stress relieve all new blocks; a used block is seasoned, so it has been stress relieved through repeated thermal cycles. Stress relieving removes the stresses that were introduced into the block during the casting process. Once the block has been stress relieved, it is best to take your time machining it so that you don’t introduce any more stresses into the block. Take two cuts, not just one. Take three cuts instead of two. Try boring the block in the cylinder sequence of (driver-side bank) number-3, -7, -1, -5.
High-Performance Gasket Options
In the past, high-horsepower A-engines used very high compression ratios (12:1 or higher), and it made cylinder sealing difficult. New O-ring designs made running these high compression ratios for racing feasible. Then the aftermarket made head gaskets with the O-ring built in (Fel-Pro, for example). Next, the aftermarket (Fel-Pro and Cometic, plus others) introduced the multi-layered-steel (MLS) version, which was the best of both worlds. Then Mopar Performance introduced the six-bolt block (versus the standard four-bolt block) and the problems have disappeared. Note: Four or six bolts around each cylinder.
If you want to use an O-ring, however, they are generally used with copper head gaskets. You use a .032-inch-thick stainless steel wire. The machine shop must cut a groove around each bore that is .032-inch wide and .017-inch deep. The round wire sticks above the deck surface and with the proper gasket (copper), they work very well. In practice, it is more common to O-ring the cylinder head (rather than the block). Do not O-ring both.
On used blocks, you need to replace the pressed-in distributor bushing. On a new block, check that it has a bushing pressed in properly. It is poorly oiled and takes a lot of abuse in performance applications so it is best to replace it in any used block. If it is worn, it affects the ignition timing and allows the camshaft a walk. This movement changes the cam events that you try so hard to control.
You can use the intermediate shaft and gear to test the distributor bushing. Lower the gear into position just above the cam where the gear is not engaged. This position is about 1 to 1.5 inches raised above the gear’s seated position. Try to wiggle the shaft in different directions.
You can also practice the gear install. To lower the shaft and gear into position, the gear rotates. The slot in the gear is supposed to be pointing at the first intake-attaching bolt on the driver’s side once it gets into position. This takes some practice to get this to occur.
Generally, the last step in the engine disassembly process is to spin the crank once the rod-and-piston assemblies are removed. The engine builder tends to notice a tight spot during the general disassembly, but the final spin is confirmation. If no tight spot is observed during the disassembly process, the align-boring operation is not required. It is required if the block has been welded upon or suffered a major failure.
Sonic Testing
Sonic testing uses sound waves to determine the cylinder wall thickness around the bore. Thus it tells you how thick the bores actually are and if there is any core shift, and if there is core shirt, which direction it is in. If you are building many engines, buy a high-quality sonic tester; otherwise have your machine shop sonically test the block. The major thrust area on the driver’s side of each bank should be tested.
By determining bore thickness, you can figure out how much overbore is safe and where to stop. If you have two or more blocks, it tells you which one is best. Always sonic test before you start the overboring process. If a cylinder is found to be too thin, re-sleeve the cylinder or use a different block.
Sleeving
You can use sleeving as a repair or as a bore change.
Once the block is cleaned, the machine shop may tell you that one or two of the block’s cylinder bores are damaged and need to be fixed. Basic wear and/or scoring in the bore are the most common causes. No matter the reason, sleeving by a machine shop should fix it. If the process is executed properly, the rebuilt engine should be as good as new.
There are no 318 race blocks and the smallest 340/360 race block bore is 4.00 inches. The 318 block cannot be bored out to a 4.00-inch bore (3.97 inches on pre-1973 blocks but only 3.94–3.95 on 1973 and newer thinwall cast blocks). Perhaps your current race engine is worn-out; its last rebuild was at the maximum bore size for this block and it is time for another rebuild. Do you scrap the block? Sleeving all eight cylinders is one solution.
As the open loads went past 500 pounds, the friction went up and the racers wanted to use 50-mm roller cam bearings. With the 50-mm roller cam bearing, all the bearings are the same size and the inside diameter of the bearing itself is about the same, but the roller bearing is larger in outside diameter and this means the block must be machined for bigger bearing diameters. Most stock production blocks do not have enough material in this area to allow this to occur. This feature was added to all R-blocks. (Photo Courtesy R. Koffel)
The production main caps are cast all together and then cut apart. They are rough machined and then installed onto the block for final machining. The number-5 cap (on right) is the most obvious. The other four caps look very similar.
The number-3 cap takes the crank’s thrust, so it is machined differently than the -1, -2, and -4 caps. The number-3 cap on the left has the front and rear faces machined to accept the flanged thrust bearing. On the number-1, -2, and -4 caps (cap on right), there is no relief for the thrust bearing flanges.
The number-5 cap is the most complicated. The rear oil pan seal installs across the top at the bottom. The crank flange is below this surface and not part of the cap. The main cap bolts are toward the top left and middle right. The oil pump bolts to the two threaded holes (center top and middle left) and the oil passes through the hole between these two attaching holes.
The first step in building up a short block is to install the main bearings. Actually, you install the upper shell, which has the oil hole in the center and the groove around the face from side to side. It is very important that each oil hole line up with the hole in the block. The groove helps spread the oil and oil pressure around the crank journal. The other shell goes in the cap itself and does not have the hole and usually does not have the groove.
What if you want a race block with a bore of 3.97 inches (a .060-inch 318)? For small bores or worn bores, sleeving is a reasonable approach. For example, if you want to build a 310-ci A-engine with the readily available 3.31-inch stroker based on the 360/5.9L block (original 4.00-inch bores), you need a 3.86-inch bore. Sleeving is the only way to accomplish this bore size.
The typical main cap is made of cast iron (high-nickel alloy), similar to the block. Most race blocks use four-bolt caps, which may be steel or ductile iron. The number-3 cap is specially machined to accept the thrust bearing on the front and rear faces. The most complicated cap is the number-5.
Heavy-Duty Main Caps
All production blocks have cast-iron main caps with a tensile strength of approximately 241,000 psi. The tensile strength of ductile cast iron is about 413,000 psi, or more than 70 percent higher. Making main caps out of ductile cast iron results in a big strength gain. Most R-family race blocks use special upgraded heavy-duty caps (ductile iron or steel). Also, the 360 and 5.9L engines, which have the larger main diameters, should also have the main cap bolts spread .31 inch farther apart than other engines.
The tricky part with the mains caps is that they must stay in order: number-1 cap on the number-1 main bulkhead, etc. Cap numbers-3 and -5 are easy, but the other three all look alike. The production engineers had the caps’ number cast into the top of the cap, 1, 2, etc. Since the mid-1980s, the caps have two numbers on them: one for the V-8 version and one for the V-6 version (“4” on V-4s and “3” on V-6s). Without cast numbers, you would have to stamp the main number onto the cap once installed. The cast numbers on the caps are fuzzy and difficult to read.
The main cap bolts are 1/2-13. The Magnum uses a slightly smaller head on the number-5 cap bolts (at the top). The most unique main cap bolts are the ones used on the number-2 and -4 mains on the 340/360 engines when the windage tray is used. The head of these bolts is thicker and is machined to accept to small screw that is used to hold the windage tray in position.
Splayed Main Caps
Many years ago, the splayed cap was used to add the four-bolt main caps to stock-style blocks. The angle was designed to go to the outer wall of the block, below the pan rail where there was enough material to hold this size of bolt. In these blocks, the bulkhead did not have enough material for four vertical bolts.
At one time, the X and R race blocks were readily available with the added thickness in the bulkhead and the vertical four-bolt main caps, but the splayed cap is rarely used today.
Neither approach works on the Magnum blocks because there is not enough material below the pan rail in the outer wall to support the 1/2-inch bolt. However, Chrysler/Mopar has tested the two-bolt Magnum blocks at very high outputs without problems (in the range of 500 to 550 hp).
A splayed main cap is a style of four-bolt main cap, and it has the two outer bolts angled or machined at a different angle than the two inner bolts. With a splayed-style cap the outer two bolts also tend to be shorter so that the cap itself has a down-step from the standard height inner bolts. This step gives the splayed cap a unique appearance.
You can convert your two-bolt main caps to four-bolt caps. To do so, the two outer holes are drilled at 7.06-inch centers and centered on the main bearing bore. Drill the 27/64-inch hole, 1.32-inch deep and then tap with a 1/2-inch-13 tap, 1.19-inch deep. At the top, or parting line surface, add a counterbore .52 inch in diameter, .12-inch deep (T/A and X+R blocks only).
Heavy-duty main caps, such as those offered by ProGram Engineering, should be used on nitrous and supercharged applications. For naturally aspirated engines, the switch is related to RPM and stroke length. Install heavy-duty main caps if mechanical roller cams are used or if the valve lift is more than .600 inch.
Four-Bolt Main Caps, Vertical
The key to installing or using a four-bolt main cap is to have the material added to the main bulkhead to allow this modification. Only the 340 T/A block and the new X- and R-block have the added material on main bulkheads number-2, -3, and -4. The majority of R-blocks come with four-bolt caps.
Special Features and Operations
The A-engine small-block started production in 1964 and the Magnum engine’s production ended in about 2003. That’s almost 40 years of production. Over such a long period of time, some problems inevitably pop up, and they may only apply to a few engines.
Cam Bearings
When race cams became much bigger, valvespring open loads went from 750 to 1,000 pounds. And this creates two problems. First, the cam’s nose must fit through the inside diameter of the cam bearing, but bigger cams have bigger and thus higher-lift cam lobes. To gain the higher lift, using the standard or 50-mm bearings, the cam lobe’s base circle has to be ground down. Obviously with less material, the cam becomes weaker.
Rear Main Seal
The neoprene or rubber rear main seal replaced the rope seal that was installed on A-engines during the first few years of production. No one services the rope seal in gasket sets anymore. The rubber seal has a lip and must be installed in the proper direction. The rubber seal is better (with one exception).
Little grooves are machined into the rear-seal groove-sealing surface on the crank (see Chapter 2). Grooves are not commonly found on a used crank. However, if you have a brand-new crank, there is a chance that these little grooves are cut too deep, too long, or have too sharp of an edge. In this situation, the rubber seal leaks. The solution is to install a rope seal. Contact Best Gaskets in California; they still offer rope seals.
Second, the higher spring loads caused deflections, and that inhibits engine performance. So racers went to 60-mm roller cam bearings, and an R3 race block was required. The large bearing diameter allows the lobe to become larger without grinding down the base circle. This bigger base circle makes the cam stiffer and stronger.
Standard cam bearings from manufacturers such as Clevite, Speed-Pro, and Dura-Bond work fine for all street/strip applications. Although not required, you should replace the cam bearings in used blocks. Roller cam bearings are not required for the street or street/strip engines but need to be used in race engines with mechanical roller cams with valve lifts more than .650 inch.
Block Drain
A small, threaded, solid plug is at the bottom of the water jacket, near the pan rail, on each side of the block. They are only removed when the block is cleaned or hot-tanked. If the engine is to be raced, consider replacing this solid plug with a block drain, available at any standard auto parts store.
Siamesed Bores
A few blocks are cast with the bore walls joined. These special blocks are called siamese-bored blocks. The bore walls of adjacent cylinders are joined solid. This allows for slightly larger bores. It also makes the cylinder bores somewhat stiffer. The negative thing is that they cut off water flow around the cylinders, especially on the two center cylinders on each bank.
Fasteners
Bolts hold the Magnum engine; race heads use main cap bolts that are longer than the standard long bolts in production A-engine heads. ARP, A1, and other aftermarket companies sell studs that replace these bolts, and provide higher clamping force.
The studs’ biggest advantage comes into play if you race the engine and normally pull the caps to check the bearings or pull the head to check seats or guides or to modify it. Typical street or dual-purpose engines are assembled and run for many thousands of miles over a long time. Because the engines tend to be disassembled infrequently, there is very little wear and tear on the threads by the bolts.
