|
Dear 940 4ever,
Good p.m. To maximize cylinder capacity and so power, the designers of "interference engines" allow pistons more upward travel. If the timing belt breaks on an "interference engine", the valves cannot move out of the way of the pistons, which - of course - continue moving for a brief period, after the valves stop moving. The rising pistons hit the valves, bending them.
At very best, the head has to be pulled and the bent or broken valves and/or valve guides replaced. At worst, if pistons have been badly dinged, they too, must be replaced. This is a hugely costly job. In most cases, it is cost-effective to replace the engine.
On a non-interference engine, the pistons' upward travel ends before the top of the piston can touch the valves. Thus, when the timing belt breaks on a non-interference engine - and the valves are left hanging down - they are not touched by the pistons.
In this situation, one turns the crankshaft by hand to move the pistons into the right position relative to the valves, installs a new timing belt, and the engine is as good as the day it left the factory.
Hope this helps.
Yours faithfully,
spook
|
