Ok so this should remove some of the miss information about timing belts tensioners and water pumps. and the how too choose the right belt, tensioner, water pump, timing belt combo
head heights
b7/a6 95mm
D14a2 95mm
D16y3 95mm
d16z6 93mm
D16y7 93mm
D16y8 93mm
D16y5 93mm
D15Z1 93mm
for every 1 mm of head height difference you will need a 2mm more belt because it has to go up and also down
the head height information is from the factory service manuals
B2/B7/A6 tensioner OD is approx 56mm
Z1/Z6/Y7/Y8 tensioner OD is approx 52.5mm
edit: SWAPPING TENSIONERS DOES NOT WORK! the slot and the holes do not align correctly so this is not a possibility
VX ie z1 is 103 teeth
d15b2/b7 tb is 106 teeth.
A6/sohc zc TB 107 teeth
Z6/y7/Y8 TB 104 teeth
d16y7 is indeed the same size as the y8 and z6
Z1/b7/z6 have same water pump gear size
d16a6/d15b7/SOHC ZC same head height
d15b7/b2 with 93mm head
any 93mm head on a d15b7/b2 block, use a 104 tooth belt from the y8/y7 or z6
because the head you are swapping on is shorter than the normal head you need a smaller belt to get the right tension.
other notes
all cam gears are the same size! changing them will only change the centerline of your cam
if you do want to set the right centerline of the cam degree your cam, as seen here
http://www.d-series.org/forums/diy-forum/108399-diy-degree-your-cam.html
the d16z6, d16a6, d15b7, d15b2 all use a cam gear that is indexed the same
the d16y7, d16y8 both use a cam gear that is 4.5 * or half a tooth off that of the d16z6, d16a6, d15b7, d16b2
head heights
b7/a6 95mm
D14a2 95mm
D16y3 95mm
d16z6 93mm
D16y7 93mm
D16y8 93mm
D16y5 93mm
D15Z1 93mm
for every 1 mm of head height difference you will need a 2mm more belt because it has to go up and also down
the head height information is from the factory service manuals
B2/B7/A6 tensioner OD is approx 56mm
Z1/Z6/Y7/Y8 tensioner OD is approx 52.5mm
edit: SWAPPING TENSIONERS DOES NOT WORK! the slot and the holes do not align correctly so this is not a possibility
VX ie z1 is 103 teeth
d15b2/b7 tb is 106 teeth.
A6/sohc zc TB 107 teeth
Z6/y7/Y8 TB 104 teeth
d16y7 is indeed the same size as the y8 and z6
Z1/b7/z6 have same water pump gear size
d16a6/d15b7/SOHC ZC same head height
d15b7/b2 with 93mm head
any 93mm head on a d15b7/b2 block, use a 104 tooth belt from the y8/y7 or z6
because the head you are swapping on is shorter than the normal head you need a smaller belt to get the right tension.
other notes
all cam gears are the same size! changing them will only change the centerline of your cam
if you do want to set the right centerline of the cam degree your cam, as seen here
http://www.d-series.org/forums/diy-forum/108399-diy-degree-your-cam.html
the d16z6, d16a6, d15b7, d15b2 all use a cam gear that is indexed the same
the d16y7, d16y8 both use a cam gear that is 4.5 * or half a tooth off that of the d16z6, d16a6, d15b7, d16b2