timing gear question
Posted: Sat 29. Mar 2008, 10:50
I want to replace a noisy timing gearset in my R60.
Here is the problem from my understanding.
The factory matched a gearset to the crank case in this way:
1) after machining the case, the centre distance between
crank and camshaft journals was measured and the case was
stamped with the deviation from the specified value in
hundreds of mm (+2 stands for 0.02 mm larger than target
value).
2) The gears were mounted as a pair in a rig - there may
have been pre-sorting of individual gears or it may have
been just random combinations. With the correct backlash
adjusted in the rig, the deviation from the ideal value was
measured and THE PAIR was marked with numbers accordingly
AND kept as a matched set.
3) The assemblers then selected a CASE and a GEARSET marked
with the SAME numbers.
Given this assumed procedure, it is meaningless to combine
gears of unknown origin, i.e. from different engines, even
if the markings on the gears and case display the same
numbers. In other words, the cases are always determined by
their number but the gears' markings are only valid as an
originally matched pair.
This is my question:
Does anybody know the required backlash of the timing gears?
I have not found anything regarding this in the literature.
With that knowledge it would be possible to re-establish a
match, given one has enough individual gears to choose from.
Here is the problem from my understanding.
The factory matched a gearset to the crank case in this way:
1) after machining the case, the centre distance between
crank and camshaft journals was measured and the case was
stamped with the deviation from the specified value in
hundreds of mm (+2 stands for 0.02 mm larger than target
value).
2) The gears were mounted as a pair in a rig - there may
have been pre-sorting of individual gears or it may have
been just random combinations. With the correct backlash
adjusted in the rig, the deviation from the ideal value was
measured and THE PAIR was marked with numbers accordingly
AND kept as a matched set.
3) The assemblers then selected a CASE and a GEARSET marked
with the SAME numbers.
Given this assumed procedure, it is meaningless to combine
gears of unknown origin, i.e. from different engines, even
if the markings on the gears and case display the same
numbers. In other words, the cases are always determined by
their number but the gears' markings are only valid as an
originally matched pair.
This is my question:
Does anybody know the required backlash of the timing gears?
I have not found anything regarding this in the literature.
With that knowledge it would be possible to re-establish a
match, given one has enough individual gears to choose from.