Service 05 of 11
Cylinder head and valvetrain
Lost compression, blue smoke or rough running often have their cause in the cylinder head. We take the head off, strip it and check flatness, valve seats, guides and camshafts — before anything is reworked or renewed.
The measurements we take on the head — guide clearance, seat width, flatness — are on the page “The engine you can pull apart”.
Symptoms
How you notice trouble in the head
Blue smoke on start-up
A blue cloud after starting that clears: usually worn valve stem seals or guides. On a flat-six, a small puff after the car has stood for a while is normal.
Lost compression
One cylinder compresses less than the others. Often it is leaking valves or sunken valve seats.
Rough idle
The engine shakes and the fault memory shows misfires on one cylinder. If the ignition is sound, it can be a valve — the compression test shows it.
Ticking from the valvetrain
A light tick that follows the revs: too much valve clearance, a worn hydraulic tappet or worn cam lobes.
After overheating
The sealing face can warp, and cracks can form between the valve seats. A new gasket on its own will not fix that.
Not sure it is the head?
A compression and leak-down test shows it before anything is stripped. Write to us with what you have noticed.
Send a message
Scope
What is done on the head
The head is stripped completely, cleaned and measured. What lies outside the specification is reworked — no more and no less.
- Head removed, stripped completely and cleaned
- Sealing face checked for flatness, the head for cracks, skimmed if needed
- Valve guides measured, worn guides renewed
- Valve seats recut, valves checked or replaced
- Valve stem seals renewed as a set
- Camshafts, bearing journals, valve springs and rockers or tappets checked
- Valve clearance set, where it is adjustable
- New gaskets, new head bolts where specified, fastened to specification
Method
Four steps
- 01
Inspect
Compression and leak-down tests, borescope. That way it is clear the head is the problem before it comes off.
- 02
Approval
Scope and cost in writing, labour and parts separately. No part without your yes.
- 03
Recondition
Strip and measure the head, rework seats and guides, renew seals as a set.
- 04
Handover
Refitted to specification, valve timing set with locking tools, test run and road test.
Questions about it
What people ask about cylinder heads
Does the engine have to come out on a Porsche?
On a flat-six, as a rule, yes: the heads sit on either side of the engine, low in the engine bay, and can barely be reached with it installed. That is why head work on a Porsche is more involved than on an inline engine, where the head sits on top and can come off in the car.
Is it enough to replace just the head gasket?
Often not. A blown gasket has a cause — usually overheating — and that has often warped the sealing face too. With the head off anyway, we check flatness, valves and guides as well. What gets reworked is decided by the measurements and your approval.
What if a valve has hit a piston?
Then several valves are usually bent, and guides and pistons often damaged too. The head is reconditioned, the pistons checked — and the cause put right: usually a timing chain that has jumped or snapped, and on a sports car also a missed shift that over-revved the engine. At that point it is an engine repair, and the head work is one part of it.
Cylinder head and valvetrain
A blue cloud on start-up?
Measure first, then take the head off.
Related
Related services
- 04
Engine repair
When pistons or bearings are affected as well as the head.
- 03
Timing chain replacement
The timing drive has to be undone for the head anyway — the moment to check chain and tensioners.
- 11
Diagnostics and fault finding
Compression, leak-down, borescope — before the head comes off.