Interference, Non-Interference.....

One tooth is enough to damage the valves on our engines. Just depends on where the valves are when it happens. There are certain piston designs that have indentations where the valves would hit, but I'm not sure if there is enough clearance with those to call it a non interference engine with them. If you really want to make it non interference it can be done, just need to check out a few rod/piston combos that will do it.

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Originally Posted by thor'svr4

you’re not going to bend any valves if you jump a tooth, and you can probably even get away with jumping 2 teeth. its when the belt snaps (EBay belt), your tensioner fails, or the tensioner pulley slips that causes the belt to jump several teeth and bend valves.

plus you notice a huge loss of power when the belt jumps 1 tooth, let alone two teeth. my RT felt like turtle one day, when I checked the timing marks all the cam gear marks lined up with the marks on the head but the crank was 1 tooth off. honestly I’m not sure what caused it to skip a tooth, but I just redid the timing belt and the car went back to its normal 'peppy' self.

I also had a Mazda 929 in which mice decided to build a nest right on the timing belt. when I fired up the car it jumped 7 teeth but the car still ran for a little bit. Even though the belt jumped 7 teeth the valves didn’t look too bad. When I took of the heads and checked it out you could only see a tiny amount of light in-between the valve and the head.

Just do your 60K with OEM parts and you’ll be fine. plus a 60K is cheeper than custom 'non-interference' pistons.

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Its a gamble on jumping teeth. My NA jumped 7 teeth without bending a single valve but Ive heard of others only jumping 2 or 3 with bad damage.

The TT engines are definitely interference engines. When my A/C belt shredded and wrapped around the front pulley and got inside the front cover wrapping around the crank timing belt drive gear i instantly lunched 24 valves. Every one of them was bent and hanging open. Zero compression, zip, nada, none.

One big factor is getting the belt tensioner at the proper setting. If it is to loose and not enough tension on the belt it could slip under certain conditions.

Do it right the first time.