Mopar Small-Blocks. Larry Shepard

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.

Motor Mounts

      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!

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