Cylinder Block & Head

The symptoms cluster and rarely appear alone. White smoke from the exhaust that smells sweet, coolant disappearing with no puddle beneath the car, a milky emulsion on the oil filler cap or the dipstick, overheating, and pressure building in the expansion tank as combustion gases enter the cooling system. A combustion gas test on the coolant confirms it in minutes without dismantling anything. Do that test before ordering parts, since a leaking hose or a failed thermostat can produce some of the same signs.

Only after checking, and the check is quick. Lay a straight edge across the head face in several directions and measure any gap with feeler gauges against the manufacturer's flatness limit. Overheating warps aluminium heads, and refitting a warped head onto a new gasket produces a repeat failure within months. Crack testing is worth doing at the same time, particularly around the valve seats and the injector or plug bores. Skipping these steps is the most common reason a head gasket job has to be done twice.

Because most are torque to yield, designed to stretch permanently into their plastic range as they are tightened so that they hold a very consistent clamp load. Once stretched they cannot reliably do that again, and reusing them gives uneven clamping across the gasket, which is exactly what a head gasket cannot tolerate. New bolts are inexpensive relative to the job. Follow the specified sequence and the angle tightening stages precisely rather than working to a torque figure alone.

Scope. A cylinder head, supplied bare or machined, is the top casting alone. A short engine is the block with crankshaft, pistons and rods fitted, ready to receive your head and ancillaries. A complete engine sub assembly includes both. Which you buy depends on what the strip found: a failed gasket with a sound bottom end calls for a head, while bore or bearing damage calls for a short engine at minimum. Read each listing carefully, since content varies.

It meters crankcase gases back into the intake so that pressure from combustion blowby does not build up behind the seals. When it sticks closed, crankcase pressure rises and pushes oil past the crankshaft and cam seals, which is why a car can develop several leaks at once from one cheap part. When it sticks open, it becomes a vacuum leak and produces a rough idle. It is one of the least expensive parts in this category and worth checking before chasing oil leaks.

Almost always because the engine overheated, and the overheating had its own cause: a failed thermostat, a blocked radiator, a leaking hose, a tired coolant pump or an electric fan that stopped running. Replacing the gasket without finding that cause simply schedules the next failure. Investigate the cooling system as part of the repair, replace the thermostat and pressure cap as a matter of course, and pressure test the system before the car goes back on the road.

PCV valves, hose clamps and lifting hooks sit right at the bottom of the range. Cylinder head covers are modest. Machined cylinder heads cost considerably more, and complete engine sub assemblies sit at the top of the category, shipped as heavy freight. The live minimum and maximum are shown in the band at the top of this page. For the larger items the quote form is worth using even where a price is shown, since transport is a real component of the total.

It is a long job rather than a highly skilled one, and it rewards patience and a manual. The tasks that catch people out are getting the timing drive correctly marked and reassembled, cleaning both faces perfectly without scratching aluminium, checking head flatness properly, and following the bolt tightening sequence and angle stages exactly. Budget a full weekend and a set of new bolts, gaskets and seals. If the head needs machining, that is a trip to a specialist in the middle of the job.

Only where the number agrees. Engines within one family share a name and differ in bore, compression ratio, port shape, valve size and sometimes bolt pattern, and a head that bolts on with different ports or chambers changes the compression ratio and the way the engine breathes. Fuelling and ignition maps will not match it. Read the number cast or stamped on your own head, match it exactly, and use the quote form where the reference brings back nothing.

Carefully, and never with an abrasive disc on an aluminium face. A rotating abrasive removes metal unevenly and embeds grit in the surface, which ruins the flatness you are relying on. Use a plastic scraper, a solvent gasket remover and patience, keeping debris out of the bores and the oil and coolant galleries by stuffing them with clean rag. Finish by wiping both faces with a lint free cloth and solvent, and check flatness with a straight edge before the new gasket goes on.

Yes, and the schedule matters most in the first few hundred miles. New rings need controlled load to bed against the bore, which means varying engine speed, avoiding sustained constant revs and avoiding both very light and very heavy load. Change the oil and filter early, since the initial bedding process releases fine debris. Follow whatever schedule accompanies the assembly you buy, and treat the running in period as part of the repair rather than an optional courtesy.

Yes. Blocks, heads and short engines are almost always handled by enquiry rather than by a listed figure, because they are heavy, they are packed individually and freight forms a real share of the delivered cost. Send the number and the reply covers transport as well as the casting. Two questions are worth answering in the same message: whether you need a bare casting or a built assembly, and whether the head has been measured for distortion. A head that needs skimming may be repairable, and knowing that before you order avoids buying a casting you did not need.