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451 Valve Clearance Checking

Mod Details
PremiumNo Difficulty Mod ID1888 For451 Fortwo Linkhttps://evilution.co.uk/mod/451-valve-clearance-checking.htm Copy to Clipboard

Smart state that the inlet and exhaust valve clearance should be checked every 56,000 miles. I have never known anyone actually do this, including myself.

That’s why there are no photos. If you do check the clearances, please take some photos and send them over.

Access

Remove the cylinder head cover to reveal the camshafts and valve tappets (also called buckets or cups. I have always called them buckets but that’s probably a British thing).

Put the engine to top dead centre and check to make sure that cylinder 1 valves are not under load. If either valves are under load, rotate the engine crankshaft by 360°.

Checking Clearance

Check the valve clearance of:
Intake valve cylinder 1
Intake valve cylinder 2
Exhaust valve cylinder 1
Exhaust valve cylinder 3

Turn the crank pulley 180°

Check the valve clearance of:
Exhaust valve cylinder 2
Intake valve cylinder 3

This should be done using a feeler gauge. A feeler gauge is a tool comprising of a many blades of varying thicknesses. They fold out separately and you just fold out the combination of the thickness you require and stack these on top of each other.

Adjusting Clearance

Make a list of clearances for all 6 valves.

Remove the appropriate camshaft and lift out the worn tappet/bucket/cup. Look on the inside of the tappet and it’ll be marked with the thickness.

You will have to order replacement tappets that are thick enough to bring the clearance back into specification. Alternatively, you can fit bucket shims if you can’t get new buckets from smart.

Repeat this process with all of the out of spec tappets before refitting the camshaft and rechecking the clearances.

Important

Do not use a magnet to remove the tappets as this can magnetise them which will cause them to collect swarf and that will increase future wear.

Clearance Figures At 20°C

Intake valves = 0.18mm to 0.26mm

Exhaust valves = 0.26mm to 0.34mm