Even though the 4D56 may be an interference engine, the valves enter the head almost vertical. Any contact with the pistons tend to push the valves straight back up which results in smashed cam caps and rocker arm, but the valves/piston remian intact/unbent most of the time.
This means you don't have to take the head off if you want to rebuild it? Cam caps and rocker arms can be replaced with the head in place, meaning you minimise the amount of work in the rebuild compared to getting a new head.
In the case of a lot of other engines, because the valves enter at an angle....the piston makes a right proper mess of everything when it makes contact. Bent valves, snapped valves embedded in the piston, smashed head from newly embedded valve being pummelled into the surrounding metalwork before the engine cuts out......
Here are some shots of the head on the Mystery Machine when the balance belt went:
Cambelt still on the pulley...
But where the balance belt had got caught in the top pulley, the cambelt had stopped turning with the engine!
This caused the pistons to smash the valves into/through the rocker arms.....
....and also smashed the cam caps (all 5 of them!!)
The cam lobe had also been smashed off:
A few sets of second hand cam caps, rocker arms and a cam meant I was back on the road with the minimum of fuss. Cam caps are machined to match the head and cam, so you need a few sets of cam caps to mix & match in order to find ones that will fit perfectly on the cam. Anytime my friend has a dead 4D56 engine, he always keeps the intact cam caps, rocker arms and cams for future rebuilds.....
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