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Discussion Starter #1
Hi there

Just after a bit of information as i noted the other day persons were spending £600+ for a service that includes the Cam belt change.

i am showing my age here as years ago i had a ford with an original overhead cam belt that had done 120k miles which the car was always being hammered. I never changed the belt and one day it snapped on me and there was no chance that at any time would the tappets hit the top of the piston, so that was why the belt was only change after snapping.

i have a 2005 mgtf 115 and i wondered that if the cambelt snapped on this engine is there a possibility that the tappet would hit the pistons. if it is not the case it seems an expensive way to renew belts when you might as well wait until it snaps.

i am also aware that the rubber on the belts perish over time but how many has actually had a cam belt break on them.
 

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Discussion Starter #3
Thanks David, are you sure that damages to the piston would take place if the cam belt snapped? They always said the pistons would be damaged on the Ford engine. After my belt broke i spoke to various persons and they said you were lucky that the overhead cam must have been in a position when the belt snapped that all tappets would not hit the pistons. After going into great details with the ford technical bods they said that most people thing damage will occur when a cam belt breaks but it is not true
 

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The K series, like most 15 valve engines is an interference engine.

If the belt breaks at tickover you may get lucky, but generally you will at the very minimum bend a few valves, but will most likely damage pistons or worse as well.

Some Ford engines were non interference, so you may have had one of those, or just been lucky if it was an interference type.
 

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The tappets or hydraulic lifters do not come into contact with the pistons in the event of a cam belt failure. HOWEVER:

The valves will, and most probably bend. From what I'm told this is because the K-series engine is what is called an 'interference' set up whereby the valves open and close between piston strokes, put they do so into the space that the piston occupies on its up strokes also. Get the engine out of time (as happens with a broken cam belt) and the two try to occupy the same space at the same time and the looser is always going to be the valves.

When changing the timing belt (or cam belt as others call it) it is also a good idea (i.e. don't change the belt without doing this!) to get the timing belt tensioner changed as well (the bearings have a habit of failing and causing the cam-belt to lose timing and break the engine just as if the cam belt had snapped) - and also the water pump (it is not unknown for water pumps to sieze up during their lifetime and take the cam belts with them).

Doing these two 'extras' at the time of cam belt change is a good idea given the costs of doing the jobs individually at a later stage even if your engine isn't broken by failure of said part!
 

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Thanks David, are you sure that damages to the piston would take place if the cam belt snapped? They always said the pistons would be damaged on the Ford engine. After my belt broke i spoke to various persons and they said you were lucky that the overhead cam must have been in a position when the belt snapped that all tappets would not hit the pistons. After going into great details with the ford technical bods they said that most people thing damage will occur when a cam belt breaks but it is not true
I concur with the two previous posters, and I will add that I also had a Ford and that also had a non-interference engine (basically the valves at full open will not hit the piston at tdc) ie If the cambelt goes, the piston can't hit the valves.
David
 

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I concur with the two previous posters, and I will add that I also had a Ford and that also had a non-interference engine (basically the valves at full open will not hit the piston at tdc) ie If the cambelt goes, the piston can't hit the valves.
David
It wasn't a Ford CVH engine then - if they had cambelt failure - even at idle speed, both valves and pistons were often toast.
 

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It wasn't a Ford CVH engine then - if they had cambelt failure - even at idle speed, both valves and pistons were often toast.
Beat me to it!

Ours happened just before the Blackwall tunnel in East London just prior to rush hour.....not nice to hear yourself on the radio in this situation! :shake:
 

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I had a 1.4i Nova cam belt snap on me, but did not bend any valves.
My mates clio belt snapped and that did some damage. So was scrapped and my mates 106 GTI belt snapped and that bent all the inlet valves marked the head too so required a new head.
The k-series isn't a safe engine if the belt snaps as I got a gearbox from a 416 with snapped belt and the head was in the boot with bent valves.

Its a must do in my books if its needs replacing for age, miles or not known.
 

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This is the cylinder head with camshaft cover removed. The circular things that llook like silver disks here are the tappets. They are ABOVE the valves etc. The pistons are BELOW the valves in the block

 

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Cowabunga! :yikes: :errx2:

The frightening thing is that all that's stopping that happening to our engines is a rubber band (OK with a little bit of steel inside) :err:
 

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My god, thats mental.

What also scares me is that your head and block are essentially seperated by some silicon glue beads :lol:
 
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