is it not any conspiracy behind it ?
I can not imagine any technology-related reason to do it this way other than to limit reasonable person ability to repair this damn thing.
It’s cost driven. Minimizing cost to build to be more specific…
Because there is no reason it needs to be indexed. The timing is electronically controlled, triggered by a wheel on the crank and compared to a trigger on the cams. There is no way to change the timing mechanically so no timing mark needs to be visible. And, as @TwinTurbo said, it is cheaper.
It is not about timing marks, it is about the sprocket on the crankshaft having no mechanical index (or “pin”) to affix its position, thus allowing for the sprocket (plus chain, plus camshafts) to get disattached from the crankshaft, which is terminal on the interference engine.
1 Like
The absence of pulley keys allows adjustment during assembly and more accurate valve timing for cleaner emissions.
The old Chrysler 3.5 L engine didn’t have keyed camshaft pulleys, if a cam pulley was remove a special tool is needed to align the camshaft during reassembly, the pulley is tightened down with the timing belt in place. The ability for adjustment makes up for manufacturing differences in timing belts/chains and pulleys.
Meh. The same could be achieved by tighter specs on the parts. Loosening those specs reduces parts cost. The infinite adjustability and critical assembly process replaces the need for more expensive parts. The impact to the consumer is a more demanding repair process that is intolerant of mistakes.
1 Like
For what it’s worth, in the days of the old Cadillac big blocks (472, 500, etc) the harmonic balancer was installed without a bolt to hold it onto the crankshaft nose.
The nose was threaded but they came from the factory with a press fit only.,
Good points above about the ass’y and adjustment benefits of the diamond washer approach vs keyed-pulleys. Since this appears to be a pretty common configuration, seems odd a transmission shop wouldn’t be aware that it presents some mechanical complications whenever the crankshaft pulley is removed. I’ve never heard of this configuration before myself, so I could see how I might make that mistake were I to do that job w/out consulting the service procedure. The timing belt pulley is keyed to the crankshaft on my Corolla’s 4afe engine fortunately.