Is there really any need to run the car to your dealer once fitting a new cam belt to check it tightness, or will the 90 degree twist suffice ?

Pat...

Depends entirely on the car.

VAG diesels use an automatic tensioner, where you twist the eccentric portion until 2 marks line up. Tension is set by the clockspring inside.

Other cars (Pinto being one of them), you have to do it manually. I think Facom do a tension measuring kit, but it uses arbitrary numbers as a measure (i.e. just numbers 1-5 with no units), rather than something useful like newtons.

What car is it?

Renault Scenic 1.6 Petrol.

Has a little pulley with an off centre hole for adjusting the tension and it's tight enough to allow a 90 degree twist.

Don't know whether to put the cam cover back on etc. and take it to the Renault garage.

Pat...