new vanos exhaust hub & spline gear install

[4getr34]

what is the procedure to find the "sweet" tooth on the spline gear against a new exhaust hub?
I saw a couple of vids on marking against original hubs but not while installing a new one. Can someone point me to a video?

[mrgizmo04]

https://www.beisansystems.com/procedures/s54_vanos_rattle_procedure.htm

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[4getr34]

thats on an old hub and dosn't go into finding the ideal tooth

[maupineda]

process is the same old and new, unless the new one is cut to a different spec, just spin the spline around until it goes right in without rotating the hub.

[eacmen]

The sweet tooth theory has been debunked several different times.

Follow the procedure and you’ll be fine. Don’t lose sleep over trying to find the sweet tooth.


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[sapote]

Finding the sweet tooth is a waste of time for no good reason. Use the time instead for doing a good timing without removing the vc and retime again.

[x Spades x]

The sweet spot is pushing the the spines without rotating the hub.

[mrgizmo04]

The sweet spot is pushing the the spines without rotating the hub.

You have to rotate the hub because the gears are not straight cut

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[x Spades x]

You have to rotate the hub because the gears are not straight cut

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I've been doing this process over the past month. I've found the sweet spot about 70 times in the last 30vdays (I can do it without even looking now). When you line the spline up, its basically synce up with the gear so well that if you just push in, the spline slides in and bottoms out. If it doesn't do that, you are 3 gears off (very next turn) from sweet.

[mrgizmo04]

I've been doing this process over the past month. I've found the sweet spot about 70 times in the last 30vdays (I can do it without even looking now). When you line the spline up, its basically synce up with the gear so well that if you just push in, the spline slides in and bottoms out. If it doesn't do that, you are 3 gears off (very next turn) from sweet.

70 times - on the same car?

When you push the spline in, the hub rotates ccw, right? The back end of the splines is straight cut and goes into the throat of the cams (which are stationary and don't rotate), while the angle cut helical part of the spline interacts with the hub. Since the spline does not rotate (held in by the cam), the hub has to rotate to mate and allow the spline to get to that "bottom out" state. Sweet tooth or not, it will still bottom out.

I was just questioning your original post that sweet tooth means hub doesn't rotate, I'm just not sure how that makes sense.

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[x Spades x]

70 times - on the same car?

When you push the spline in, the hub rotates ccw, right? The back end of the splines is straight cut and goes into the throat of the cams (which are stationary and don't rotate), while the angle cut helical part of the spline interacts with the hub. Since the spline does not rotate (held in by the cam), the hub has to rotate to mate and allow the spline to get to that "bottom out" state. Sweet tooth or not, it will still bottom out.

I was just questioning your original post that sweet tooth means hub doesn't rotate, I'm just not sure how that makes sense.

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70 times on my car, as I got a new engine and swapped the head internals, etc. Yes, timing bottom end, cams, vanos etc etc... I've done this process a mind numbing amount of times.

Yes, you turn the hubs all the way clockwise (as far as it goes. Out of all of the teeth, there are only two positions that one could think is the sweet spot. One you need to BARELY move the hub CCW to push the spline in... and the other looks to line up perfectly before pushing in. You can then push without even touch the hub to turn it. THIS is the sweet spot.

While pushing in the spline, the hub will continue to turn CWW as in bottoms out.

[4getr34]

thanks guys, i did this last night.

found two great visual resources.

https://www.youtube.com/watch?v=kbX1vfki75g

https://www.youtube.com/watch?v=7xh7aJl1OxQ

for the intake/original hub, pushing spline against the sweet tooth requires almost no rotation. the threaded end of the spline shaft sits flushed with the hub surface.
for new exhaust hub (besian), there is rotation ~ 1mm to push spline in. the threaded end of the shaft sits flushed with the bottom of the hub tabs.

flushed position visualized.

https://www.youtube.com/watch?v=ze5sOob6H6E

[eacmen]

thanks guys, i did this last night.

found two great visual resources.

https://www.youtube.com/watch?v=kbX1vfki75g

https://www.youtube.com/watch?v=7xh7aJl1OxQ

for the intake/original hub, pushing spline against the sweet tooth requires almost no rotation. the threaded end of the spline shaft sits flushed with the hub surface.
for new exhaust hub (besian), there is rotation ~ 1mm to push spline in. the threaded end of the shaft sits flushed with the bottom of the hub tabs.

flushed position visualized.
https://www.youtube.com/watch?v=ze5sOob6H6E

The fatboys garage video series has some good tricks in there. Fatboys video coupled with the biesan doc you can’t go wrong.


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[4getr34]

yeah they had some great tips. they mentioned subtle things like filing down a 24mm wrench to rotate the cams. also you can tell they were experienced pros as certain techniques were slightly different - checking timing tool clearance using feeler gauges, tapping out vanos end covers with mallet, etc..

[sapote]

for the intake/original hub, pushing spline against the sweet tooth requires almost no rotation. the threaded end of the spline shaft sits flushed with the hub surface.
for new exhaust hub (besian), there is rotation ~ 1mm to push spline in. the threaded end of the shaft sits flushed with the bottom of the hub tabs.
]

Why do you care if the hub has to be rotated slightly CCW in order to insert (line up) the splines, or if the hub doesn't need to rotate?
Fact: the sprocket has 6 long slots and not just round holes as shown in pic below. So with the hub turned to max CW and the hub bolts are touching the right end of the slots. When inserting the splined shaft, you only need to turn the hub slightly (less than one tooth) CCW to line up the splines with the shaft, and so there is plenty the slot range for the hub to turn CCW further when the final VANOS module is bolted to the head, and then torque down the hub bolts. So don't worry about finding the sweet tooth, as there is still slot left after final torque down the hub bolts which are not touching the left end of the slots.