Went to get fuel last night, after filling up I floored it in 1st gear away from the garage but when I changed into second there was an almighty bang from the engine and it would only run very badly. I got towed back to my garage abandoned it in disgust.

I lifted the can cover this morning to find the exhaust cam had snapped in between cylinder 2 and 3! I took the cylinder head off and there are no bent valves or marks on the pistons.

Any idea what could have caused this as the rev limiter is set to 6500rpm so was not over revved ?

I am running a 2L Zetec (silver top) with TD04 turbo running 12psi.Image deleted by owner

Two possibilities come to mind :-
1)
It is possible that who ever fitted the cam did not fit it properly. It is possible that either it was bolted down totally at one end first or with some valves initally touching somewhere so that it was stressed and given a stress fracture.

Or

2)
When manufactured it had a casting or billeting fault in it to begin with.

The only way to be entirely sure on either of the above would be to carefully both faces of the fracture for tell tale signs.

Oh and for information purposes I have managed to break a cam shaft before on a Vauhall Senator 3.0l 24 valve by method one, despite having done everything by the book. When the replacement arrived (£425) I threw the book away and did it my way by using Mk1 eyeball and working the maths out in my head. Perfect first time on second attempt. (Bloody dealer workshop manuals).


Edit bit
3rd possibility, head warp??? check journals with a straight edge. And check centre bearining cap (next to breakage) as well.

[Edited on 13/6/10 by jollygreengiant]

Thanks for the answers, will get a new exhaust cam and see what happens.

Any ideas where I could get a standard exhaust cam for a 2.0L zetec (silver top) from? As all the local breakers either don't have any or want to sell me whole engine and won't just sell me the cam.