Pump/cam/stroke timing on any diesel is critical. <snip>A very slight difference in pump/cam timing makes a HUGE difference in performance.
with the modern electronically timed systems I am very reluctant to risk even a slight misalignment so I am willing to buy all of the tools needed to ensure peak performance.
as always, YMMV.
The large cam lock tool probably has its place if you need to do something that doesn't require replacing the timing belt. But since we are replacing it, it is better to loosen the sprockets.
We only consider 4 alignment parts (left cam, right cam, crank, pump) why would you introduce 2 more by solidly holding the cam sprockets? We know that timing belts stretch and a new belt is different from the old so let the sprockets naturally find their position along the belt. This way they are not forcing a stress due to the large locking tool or the old belt position.
My understanding is that the cam sprocket holding tool is used when the sprockets need to be removed, i.e. when the water pump is being changed. This clamp avoids both overstressing the alignment pins, and at the same time preventing unwanted camshaft movement. Some may elect to wait on WP replacement, but given the amount of time
required to remove the WP, on the CRD I will elect to change it when I do the belt.
As regards alignment, the camshafts need to be in the right relationship to each other and to the crank and the IP. I have not read up on this yet, but would be surprised if there was not a procedure to properly align the camshafts proper with the head prior to cam sprocket alignment. If the valve timing is even slightly off, or the pump timing, relative to the pistons, performance and ruling fuel economy can be suboptimal, even if the engine does not show any gross misalignment. The cam pins are there to ensure alignment, and once the clamp is off after tightening the bolts, I will be checking them AND the shaft position to be certain everything is lined up to spec, both before and after rotating the engine manually.
Going back to my experiences with the D24/D24T engines, even a very slight variation in cam/ pump timing makes a substantial difference in fuel economy. Well timed D24T engines demonstrate fuel economy in the low to mid 30s; poorly tuned ones can be as bad as the low 20s. Modern high pressure pumps are even more finicky. I suspect but have no data to prove that many of the CRD Liberties that show poor mileage are the result of slight misalignment of the camshafts.