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mrrogers

1986 928S Interference Engine

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I have found a 1986 928S with a broken timing belt. Does anyone know if it is an interference engine? I thought that the 1978 through 1984 two valve engines were not interference engines, and that the 1985 and newer four valve engines are interference engines, but I am not sure. If the engine still turns over is it safe to say that it is not an interference engine?

Best regards,

Joe

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I have found a 1986 928S with a broken timing belt. Does anyone know if it is an interference engine? I thought that the 1978 through 1984 two valve engines were not interference engines, and that the 1985 and newer four valve engines are interference engines, but I am not sure. If the engine still turns over is it safe to say that it is not an interference engine?

Best regards,

Joe

Not sure if anyone replyed to this but here we go :

All 32 valve engines are by design 'Interference' engines. 16 Valve non euro- engines are not. 16 Valve Euro engines are 'not' eiter, however they are higher compression and if carbon builds up on the valves/piston crown contact can occur if the belt breaks.

One way to test the 'broken' belt motor is to carefully re-place the belt (being sure the cams are correctly positioned (this alone could cause a bent valve as you turn the motor). After the belt is replaced and the timing is set perform a leakdown test on each cylinder. If you end up failing leakdown you likely have bent valves. Take a note of the cylinders that have failed, and remove the heads. Valves cost approx. 30 USD Per valve. You will need to replace the bent valves, and inspect the piston and head for damage. After this you reassemble and pray that this was all the damage. I would replace the Waterpump at this time, and consider a Porkentensioner instead of the factory tensioner.

YMMV.

Good luck

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