Mitsubishi Delica 2.5 TD 4D56 (1993): Cylinder Block Deck Resurfacing

Part numbers are from the manufacturer's original catalogue. Check them against your VIN before ordering.

• Socket and wrench set, torque wrench, precision straightedge and feeler gauge set, micrometer or depth gauge, dial indicator with stand, pulley puller, engine hoist
• the resurfacing itself is done on a machine at an engine machine shop

1. Determine whether resurfacing is needed. Clean gasket residue off the block surface with a plastic or wooden scraper, and do not scratch the surface with metal tools. Lay a precision straightedge along the length and across the diagonals and measure the gap with a feeler gauge. For the 4D56 block, the allowable warpage is roughly 0.05 mm and the limit is about 0.2 mm (confirm the exact values in the manufacturer's service manual). If the gap is larger, the block needs resurfacing. If it is smaller, cleaning is enough.
2. Drain the coolant and oil, then remove the intake and exhaust manifolds, injectors, timing belt and cylinder head. Loosen the cylinder head bolts from the edges toward the center, in several passes, on a cold engine so the head does not warp.
3. Remove the engine from the vehicle and take off its accessories if the machine shop requires it. In practice, the block is usually fully disassembled for resurfacing: remove the oil pan, the pistons with connecting rods and the crankshaft so that chips and abrasive do not get into the passages and bearings.
4. Before resurfacing, measure and record the original block height from the crankshaft axis (or from the oil pan surface) to the head mating surface, as well as the piston protrusion above the block surface at top dead center. This is needed so that, after resurfacing, you can select the head gasket thickness and make sure the pistons will not touch the valves.
5. Hand the block over to the machinist. Ask them to remove the minimum layer, only enough to eliminate the warpage and defects, usually no more than 0.2 mm in total for the block and head combined (confirm the exact limit in the manufacturer's service manual). The surface finish must be suitable for the head gasket. Check the flatness of the cylinder head at the same time: if necessary, it is machined too, but account for the combined material removal in your calculation.
6. After resurfacing, wash the block thoroughly and clean the oil passages and the threaded cylinder head bolt holes (blow them out so no oil or water remains, otherwise the block can crack when the bolts are tightened). Make sure the chamfers of the threaded holes and passages are not clogged with chips.
7. Measure the new block height and the piston protrusion after assembly. Select a head gasket of the correct thickness based on the piston protrusion: the more material removed, the thicker the gasket required, otherwise the compression ratio will increase and the pistons will end up closer to the valves. If the piston protrusion is out of tolerance after the layer is removed, fit a thicker gasket or consult a specialist.
8. Install the pistons, crankshaft and oil pan with new gaskets. Main bearing cap bolt torque is about 78 N·m (58 lb-ft) (approximate, confirm in the manufacturer's service manual).
9. Install a new head gasket on the dry, clean block, fit the head and tighten the bolts in several passes from the center outward, with a final angle tightening. For different 4D56 variants, values such as "29 N·m (21 lb-ft) plus about 120° turn" or "about 118 N·m (87 lb-ft)" are found. Take the exact torque and sequence for your 1993 engine from the manufacturer's service manual.
10. Install the timing belt according to the marks, then the injectors and manifolds, fill with oil and coolant, and bleed the cooling system.
11. Start the engine, warm it up and check for leaks and overheating. After roughly 500-1000 km, check the oil and coolant levels. Retightening the cylinder head bolts is needed only if the manufacturer specifies it for the installed gasket.

• Resurfacing a block is a job for a machine shop with a grinding machine
• Do not try to flatten the surface with sandpaper or a file
• Removing too much material leads to pistons hitting valves and to loss of compression
• If the gap measured with the straightedge is small, it is better to replace the gasket and tighten the head correctly than to remove metal
• Torque values in the text are approximate
• Confirm the exact values for a 1993 4D56 in the manufacturer's service manual