Big Problem! Now Solved

[spikenipple]

You can have a belt 2 miles long but as long as it stays on the pulleys the ratio won't change one bit.
The important part is the relationship between the diameters of the pulleys. The tooth pitch & diameter are calculated to give an exact rotational amount on both the crank and the cam pulley.

Been focusing on why 300k's worth of Robot wont work, so trying to recall drive train calculations is a bit hard all I could think was driver over driven, driven over driver
Basically you need the right diameter crank gear with the correct amount of teeth, anything else will throw the cams out to the bottom end.

Indeed   
So in summary, it's no coincidence that the effective diameter and number of teeth on the ABF cam pulley is precisely double that of the crank pulley   

[Screech16v]

What the nipple said ^^^

[Len]

I am replacing like for like! The crank gear off the diesel is wrong full stop!
The set up I will have (one spike has done his bit! ) will be exactly the same as on a standard abf engine.
Except for the fancy/expensive verier cam pulley!! 

[Bellend]

Once the belt is locked you could have a short belt or a 10 miles long belt, the belt is fixed so both pulleys spin at the same speed hence timing stays the same.

[VW BUSH]

Was gonna say last night, while nipples has it its worth going up a thread size on the crank gear for the bolts which hold the pulley on.
Need to clear the holes on the pulley, but its well worth doing it as the 8mm bolts snap and strip the threads very easy.

[spikenipple]

There's no need for that really. The crank pulley is hard so as long as decent graded bolts are used there won't be a problem.

[VW BUSH]

There's no need for that really. The crank pulley is hard so as long as decent graded bolts are used there won't be a problem.

That's not the reason, the tension on the belt pulley stretches the bolts and the first few threads.
Either the heads snap off when you go to undo them or the thread picks up and strips, pita when you want to do the timing belt and that happens.
I've had to do it a few times, I also stick a decent timing mark on the crank gear and pulley

[Len]

Not had a problem with those bolts! Only getting them undone!
The alllen key heads are a pain! That applies generally!

[Len]

There is one big bolt that holds this gear pulley on and that has to be tightened to 90Nm then a quarter turn! So all the stress is on that.
The four bolts only hold on the two outer pulleys for the alternater/aircon and water pump/steering pump

[VW BUSH]

There is one big bolt that holds this gear pulley on and that has to be tightened to 90Nm then a quarter turn! So all the stress is on that.
The four bolts only hold on the two outer pulleys for the alternater/aircon and water pump/steering pump

Not really, the cam belt is run with minimum tension as its a toothed drive not friction. It also is made more accurately and runs between  the cam and crank which are very accurately guided in bearings with minimal run out, critical for engine function.
The Aux belts are friction drive and subject to more run out and other conditions which equal shock and vibration transmitted through the drive. This is why you have a flange joint and cast rubber damping in the pulley to ensure the crank does not take this loading.
I could blab along for ages on this subject round a number of situations, but essentially the four 8mm bolts take a lot of stress which makes them stretch and fail in one way or another.
Maybe I should have preceded my original post with the words "if they were buggers coming out or snapped off" and mentioned just running a carbide or coated tap down the threads instead I would have made more sense.
Me being me I just see a stronger bolt with a bigger allen key size and go blazing ahead  (tampering with a deliberate weak spot without working out the full nature of my improvement, how proffesional )
Your right about the big bolt, it stops the whole lot sliding off the crank and making a big mess of things, I would fit a new one if I could just to be sure

At risk of going on and boring you and our Mk3 chums, have you considered new pulleys for your engine to maximise smooth running and efficiency? dont make me bore you with pulley wear and belt slip