Fan belt

[simon.williams]

Hi, just received a 1038mm fan belt from moss which seems slightly too small for the PI. Does anyone know what is the « standard » size? Thanks!

[johnnydog]

I think the size most suppliers stipulate is 1088mm, although some state that non PAS belts are different!
The trouble is that with many belts, the alternator sits too close to the cylinder head especially on later models, so that the belt has to be slackened/ removed to get to no.1 spark plug which is a pain. Later models had an extra packing plate under the leg of the front plate to tilt the engine over for the air filter elephants trunk which was possibly the reason why they had a narrower battery tray and battery. This obviously reduces the space for a larger battery and the space for the alternator, so maybe the new belt you have is for a late model?? On Police vehicles for example, the pulley is part no. 147530, with 154334 (2.38" diameter) listed as an alternative pulley. The belt is GFB209.
An earlier part no. for the belt on is 214239 but no measurements are listed unfortunately.
Just to complicate matters with part nos for the belt, GFB142 is also listed for the 2.5PI upto 1974 but again no dimensions are given.
Personally, I would fit the alternator in the position that is preferable and then measure the length required using a length of cord. You could then try to get a belt of the most suitable size, not forgetting that they can stretch slightly after initial use.
I have several used alternators that have different pulley diameters which doesn't help matters!
Who'd have thought that a fan belt could be so 'complicated'!

[simon.williams]

Thanks Johnny, I’ve ordered a 1088mm, hoping thats not too much the other way. If not it will just have to be third time lucky (at least they are not the most expensive components!).

[simon.williams]

It is indeed 1088mm for my mk2 PI.

[johnnydog]

Sorted!