Right I realized what's happend,basically I have had compression plates put in 1,5m thick, each head so this will explain why I couldn't get the right tension I suppose the belt is being stretchd out 3m and would also explain why belt wants to work its way off
Question is if I can find a idler pully that is 3m smaller than the standard will this give me the play I want and need??

1.5m or 1.5mm?

I'm no expert but I wouldn't have thought that 1.5mm plates would make enough difference to cause a problem.

As above. Quick question, did you rotate the floating inlet pulleys clockwise as you fitted the primary belt?

Yes buddy I did indeed
It's only solution I can think why tensioner won't set properly also the belt wanting to slip off the pullys
If it was to loose the belt would just want to slip a tooth

Right I found out the plates are 2.2m thick each head,I tried fitting a smaller idler pully today and was so much easyer to set the tensioner the belt is still trying to slip of the cam pullys but alot slower so final resort I'm going to weld a small lip on end the cam pullys

Dean,
I think you just going to have to keep an eye on the whole setup. @4.4mm its a whole tooth thats being taken up before you even start.
As we discussed you also have to watch the tension thats being applied to the water pump.
How much smaller is the one you have now fitted?

cheers
P.

Hi buddy so you would say it's a tooth out,sounds about right the smaller idler pully is 8m smaller so I am quite surprised it's still slipping
It has to be the plate the car was fine of 32,000miles before I had them put in
Altho the belts slipping off slowly the pressure has definitely been taken off the water pump,
After Bering supercharged I drove the car for 6months and it drove brilliantly couldn't fault it,car runner 250bhp with plates,when the belt went it destroyed the waterpump bearing which I assume was the tightness of the belt over time,my plane now is to weld lip on the cam pully time it with crank in safe position and the rear sprockets v faceing each other put everything back together and hopefully should run way did before without munching my belt