Contour Enthusiasts Group Archives Forums Modifications Zetec Maintenance Zetec - will valves hit pistons?

If the engine is hot, and the revs are high, you have expanding pistons and valvetrain. It is always a possibility.

One friend of mine had valves hit the pistons in a Toyota, and the thing was never really right again even after the repair, so let us not take these sorts of chances.

A visit to the Gates peplacement belt website shows the 2.0 Zetec to be a non-interference engine. This means under normal conditions I risk being stranded and towed but no valve damage. In any case, I plan to change the belt (and the water pump). I assume that any pulleys that need to be replaced are Ford dealer items - correct?? Thanks for the input.
Chas Randolph

There are many sources that cite the zetec as being non-interference, and others that say it is interference. I say, even one instance of somebody having interference happen settles the issue, and we have that now.

there are many reasons why a non-interference engine can show signs of being an interference engine. like if a if a valve spring were to break which isn't hard to do if the engine is either not well maintained or if the engine is running at high RPMs alot.

besides if we did have an interferance engine with the amount that I have seen timing being off on here most interference engine the valve would of hit the piston in some cases. I recall someones being off my 10 degrees whihc is ALOT and IF it was an interferance engine the pistons would be bye bye in that case. automotive industry has the tightest tolerances in the world most parts are made to a millionth of an inch. which makes 10 degrees seem like a mile.

and from the blue prints of the Zetec I have looked over it is a non-interference design.

Mine became an interference motor when I spun a bearing on it. Put the exhaust valves right through the piston. oh well i got another liter of power now, i'm over it.

Ten degrees??? The definition of "non-interference" is when the valves and pistons clear each other even if the angle is 90 or 180 degrees. The pistons have to be able to make a full revolution while a cam is holding the valve all the way down.

And by the way, there are no millionth-of-an-inch tolerances in a car engine. Maybe a ten thousandth or twenty thousandth, on for instance the sides of the valve tappets (which you will notice are the smoothest and shiniest surfaces in your engine).