cambelt failure

Had my cambelt snap while doing 50mph down an a road. just wondering what kind of damage i can expect?

I believe these are a non interference engine, so you might be lucky...
Simplest thing would be see if the bottom end turns over freely with a bar on the bottom pulley, if it does then do a compression test to see if you have any bent valves (you will need to rotate the cam separately to the both valves closed position to test compression)...
If you have bent the valves I have a good x20se head if you need one, or a good complete x20se engine in a sport that we got in yesterday.

Never tried it but for the money involved, you could try one of these. Take the spark plugs out and have a look for valve indention marks on top of the pistons. Doubt if you can the angle to twist it once it's inside the chambers to see the valves.
http://www.ebay.co.uk/itm/5M-7mm-6-LED- ... 0938038153

Now this is a pure guess and all but...

Rocker box cover OFF
Rockers OFF
Main Crank positioned to put the pistons at the mid point in the cylinders (Optional step really and probably doesnt bring anything to the party other than allow a reasonable view into the pots via the plug hole using a torch if the plugs were to be removed).

And place a straight edge (18" Engineer Rule or a length of STRAIGHT flat steel) across the top of the Valve Stems, I would expect them to be all level and at the same height.....

Home now. Got the timing cover off belt has not snapped but slipped off the cogs. What is the small toothed pulley at the bottom left as this is sat skewed slightly and has a lot of free play?

Bottom left if you are looking at the front of the engine, will probably be the water pump if it sits a bit higher than the bottom pulley.

Sounds like the tensioner pulley as let go. With the belt actually coming off, my money would be on the same result as if the belt had snapped, i.e. piston reach the top of the pots when the valves should have been shut and out of the way.
Now if it's a safe engine, in theory you should be alright, due to the pistons not being able to reach the valves when they are fully opened.
If it was me, I would take the spark plugs out and see if you can get a visual look at the tops of the pistons to see if there's evidence of the pistons hitting the valves. If all looks good I would try a reassemble with the components you've got, purely for testing purposes and not long term running.
If I'm right in my assumption that it's the tensioner pulley, could also be the idler pulley, it might hold to put the belt back on for short term hand testing purposes only. You will have to redo the timing, i.e. piston one at TDC with the valves on that pot in the right cycle. Screwdriver in the spark plug hole to judge the the piston is at the top of its cycle. There are some links on here to show how this works. Once, its retimed OK, and the belt back on and holding, via the crank shaft bolt, turn the engine by hand. If all free and turning over OK for a few revolutions that will be a good sign. If you doesn't and hits solid resistance, chances are a piston is hitting a bent valve. If it's all good, and if doable with hand turning pressure, then a compression test. If that's not an option, and it's your call, but if it were me, I would turn the engine on the key without revving high and let it run for a short while to see if it mis-fires or runs lumpy. Better bet and if an option, switch off and compression test each pot in turn.
If all good and your quite happy no engine damage as been done, then belt off and redo with new belt and tensioner kit. Waterpump as well would be a worthwhile investment.
All that said, if the tensioner/idler is totally knackered, unless you can borrow a spare off somebody for testing purposes, might mean biting the bullet and get the new kit from the outset. You can always reuse should you have to do valve/cylinder head repairs. Then on the plus side, if you've got away with engine damage, you'll only have to do the job once with the betting money being on the belt, tensioner and waterpump kit. You don't have to do the waterpump, but it is strongly advised when doing a new cam belt.

Thanks for all the replies, you can always rely on foggers to help out. I have tried turning the engine over by hand already, goes stiff then frees but this is normal compression isn't it? You might be right about tensioner pulley. I think the other one that looks dodgy is the water pump, it might have been this as there is lot of free movement as though bearing given up, could have thrown it off.

It is definatley a clearence engine so should have no damage. Just set up the timing marks and replace belt. While you have the belt off i would change the water pump and the spring loaded tentioner. Don't forget that on the C20NE most of the water pumps are a tentioner also.
hope this helps.
Regards Bobster.

Thanks Bobby but mine is the x20se but your right the early 2.0 is safe.Been told that the x20 is not safe and that i will have valve damage.looking at it yesterday it was the water pump thats gone buggered throwing the belt off.

Thought it was the pump...have a look, if you need a good head or engine, I can have one shipped up to you mate. Head is off, and I have another engine in a 2.0i x20se sport which has just come in that runs very nicely...

done quite a few of these and at 50 mph they do damage the engine regardless to them being a safe engine

Not heard of a redneck way to do a compression test on a engine but the kit to do it (petrol engine) sell between 20 to 30 pounds, example here

Not really...the valve lift and piston extension is constant irrespective of revs...

Managed to get an hour on it this afternoon. Trying to get the timing belt back on in order to do a compression test.

Just a question on timing, do I rotate the camshaft clockwise to align the mark with that on the back cover? Is this safe to do by hand? Whenever I have taken a belt off, this was always rotated using the existing belt and crankshaft so that it aligned. Obviously the mark is not aligned at present.

Do I set up the crank to tdc before I set the cam up?

Any tips?

Cheers, Jim

Set crank to tdc, and cam to mark, then refit the belt...Doesnt matter which way you rotate, just dont force anything.

Direction wise, can't say. But I would take the rockers off first, that way the valves arent going to move at all. Set the marks and then put the rockers back on.