Tools required : Feeler gauges, 15mm spanner, 17mm spnner, allen key for cam cover bolts

Parts required - New cam cover gasket (optional but highly recommended, the old one will probably be rubbish)

Valve clearances are an important and often-overlooked item in general maintenance but can cause significant loss in performance, fuel economy and at worst cylinder head damage. Typically though, the 'tappet' sound from a rattly top end is the reason the clearances get done.

The amount of clearance between the lobes on the camshaft and the bucket/shim/rocker/cam follower/bit that actuates (moves) the valve is set to a specific level. If this level is too small then a valve may not close fully and if it is too large the valve timing will be altered.

Not enough clearnace :

If there is no clearance at all then it is likely that the valve never closes. This may also be the case if the clearance is tighhter than the minimum allowed spec due to expansion that may occur when the cylinder head heats warms up fully. If the valve does stay slightly open, hot combustion gases may find their way past the face of the valve and burn the seats (where the back of the valve should be sealing). This will also obviously impeded performance.

Too much clearance :

If the clearance is to olarge then you will usually here a ticking sound from the top end of an engine. A tiny amount of excess clearance can make a LOT of noise too! You also find that the cam lobe opens the valve later than it should and also allows the valve to close sooner than it normal. This modification to the duration of opening/closing the valve will usually caue aperformance loss and can raise emissions and be detrimental to fuel economy.

OK so no we know what they are and why it is important they are set correctly, here is how to set clearances on a 2 litre pinto engine. You will find that there are similarties on other engines (such as older style cars including VW beetles etc) but ther are also alternative methods used on some modern cars which use 'shims'. A shim is a thin disc of metal that can be bought in various sizes to increase/reduce the clearance. Anyway, we won't cover every make/model but the principal is the same.

Step 1 - You don't have to remove the HT leads to check/alter the clearances but it can make things easier. If you are going to remove them then make sure you label them all correctly or you'll have to figure out your firing order etc to get the car running properly! Unclip the leads from the retainer next to the oil filler cap



Step 2 - Remove the leads from any cable restraints attached to the cam covers



Step 3 - Crack off all the retainers holding the cam covers in place. There should be 10 to do (shown in second picture)

Step 4 - Don't forget the one on the side of the covers near the cam belt. I undid all the nuts in three stages, one to just crack them off, then about a turn on each and then I undid them all. This is probably overkill but better safe than sorry



Step 5 - If you have limited room then a magnetic finger may come in handy for some of the harder to reach bolts once you've undone them



Step 6 - Remove the two bolts holding the water pipe onto the side of the head (anodsed red in this picture)

Step 7 - If you are leaving the HT leads attached, tuck them in front of the cam belt so you are clear to remove the cam covers. Note, you should have a cover over your cam belt unlike me!



Step 8 - The cover is now free to be removed, grab it with both hands and gently rock it towards you then away from you to break the seal the gasket has formed.



Step 9 - Now pull the cover clear of the cylinder head to reveal a world of oily bits! Careful not to get snagged on throttle cables etc

Step 10 - Ensure you pick up any old gasket that is left behind on the cylinder head (if you don't you'll creat oil leaks). On mine the arc next to the cam belt was the worst place (picture 2)




Step 11 - Now that's what I call a simple engine, one camshaft, 8 valves. It's times like these that the fancy dual overhead cam 4 valves+ per cylinder with 6+ cylinders to do don't look so great!



Step 12 - Have a look at your oil spray bar. This supplies a feed of lubrication to the cams and if it becomes blocked (usually due to poor servicing) it can cause damage to the cams. Check the little holes in it are clear

Step 13 - If you have any signs of blockage (or just want to be sure it's clear), use a pin or similar to carefully ensure all the oil holes are clear



Step 14 - I had very little clearance at the front of the engine so it was hard to get a picture but you should put a socket (or spanner) on the crank pulley bolt. This is usually the lowest pulley in the middle of the engine and in this case was a 19mm bolt. You are going to use this to turn the engine over by hand



Step 15 - It is much easier to turn the engine over if you remove the spark plugs so if you can't get good access to the pulley bolt or just want to make life easier it is worth doing this. Turn the crank over until the valve you are checking is completely closed i.e. the cam lobe is pointin away from the valve. This is always how valve clearances are normall checked

Step 16 - Use feeler gauges to ensure the amount of clearance between the bottom of the cam lobe and the valve is within specifications. Off the top of my head they were 0.10-0.15 and 0.20-0.25 but check that with a Haynes!



Step 17 - To adjust a valve, use a 17mm open-ended spanner to loosten the lock nut as shown



Step 18 - Then use a 15mm spanner to adjust the clearance. By turning clockwise, the clearance will be increase. Note that itcan be difficult to get a spanner to a couple of these so small 15 or a modified spanner can help matters. If not, persist and you wlll eventually get there with tiny adjustments

Step 19 - Note that once you have set the clearance you need to tighten the lock nut up again. This usually slightly alters the clearance so you may find holding the adjuster nut in place whilst turning the lock nut helps



Step 20 - Now just go round each intake and exhaust valve to make sure they are exactly right. Ensure you do check all valves and it is critical you get the measurements precisely right. One of my clearances was just on the borderline of being too large and I had to strip it all down after putting it back together because I develpoed a loud ticking noise. Make sure you get them right first time - it'll save time and effort in the long run!

Step 21 - Clean out the inside of the rocker cover whilst it's off, shouldn't take more than a quick wipe. In my case there was slightly milky oil due to condensation so I cleaned this all off



Step 22 - Ensure you thoroughly cean the outside edge that the gasket seals against - there should be no dirt left here!

Step 23 - Take your new rocker cover gasket (the only part you need to buy to do this job and it only costs about £2.50) and start to feed it into the rocker cover. I found it easiest to start at the front of the engine in the curved section. Simply push the dovetails into the cut outs and it should look like the second picture

NOTE : It is directional, make sure it's not upside down - you'll be able to tell because only some of the dovetails will line up with the recesses if you have it the wrong way up




Step 24 - Now carefully refit the cover to the cylinder head (you did clean up the gasket surface on the head earlier didn't you?) and rest it in position



Step 25 - Loosely fit all the allen key bolts and then torque down in the correct sequence

Step 26 - Refit the water pipe



Step 27 - And the HT leads



You're done! I checked mine after a run to ensure there were no oil leaks and that the bolts had not worked loose after being heat cyrcled. I did the same again after afew days then after a week. Everything was fine and there were no oil leaks - you should find the same if you clean up the gasket faces properly and take your time ensuring the bolts fit throughthe gasket holes.

Once you've done this job a few times it really is one of the simplest things in the world although it can seem a bit daunting at first. Give it a try and I'm sure you'll be pleasantly surprised.

I happened to do a Megane's valve clearances the other day so here's a picture of a slightly different set up :