Mitsubishi K3A–K3F Overhaul: Cylinder Head and Block

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Is your Mitsubishi K3 losing compression, burning oil, or leaking at the head gasket? Then it's time for overhaul work on the cylinder head and block. This three-cylinder engine lends itself well to overhaul: parts are readily available and the tolerances are clearly defined. Below are the key service limits from the workshop manual and what to watch out for during the overhaul.

Suitable for the entire series: K3A, K3B, K3C, K3D, K3E, K3F, K3H, and K3M.

Overhauling the Mitsubishi K3 cylinder head

Always check the head for flatness: the underside may be warped by no more than 0.05 mm, with a repair limit of 0.1 mm. When resurfacing the head, keep an eye on valve recession. The key head values:

Mitsubishi K3 cylinder head tightening sequence

The cylinder head has eleven bolts: eight M14 main bolts and three M14 bolts on the pushrod/tappet side. Always tighten them in a cross pattern, working from the center outward, in two to three steps. The final torque is 15–16 kg-m (147–157 Nm) for the eight main bolts and 10–11 kg-m (98–108 Nm) for the three bolts on the pushrod side. Always replace the head gasket when disassembling, and clean the bolt holes and threads. The diagram below shows the bolt sequence with the front of the engine on the left; the tightening sequence is the reverse of the loosening sequence.

Mitsubishi K3 cylinder block, pistons, and bearings

For the block, check the cylinder bore, pistons, rings, and bearings. The bore per variant (K3A 65 mm through K3E 76 mm) may be bored out up to +0.2 mm as a repair size and has a service limit of +0.95 mm; oversize pistons are available in 0.25, 0.50, and 0.75 mm. The key service limits:

Connecting rod and main bearings are available in undersize 0.25, 0.50, and 0.75 mm. During an overhaul, always replace the cylinder head bolts, the head gasket, and the valve stem seals, and never reuse old bolts. Take the water pump and glow plugs along at the same time — they're already off anyway.