Belt sizes

[jhoff]

Hello! I'm looking to replace the belt on my bmc 1.8. The current one has "Powertrain PCFB 860" on it, but it seems like Powertrain is not really a thing anymore and I'm having trouble finding other belts that are 860mm.

Any suggestions? If I cannot get the exact same length is it better to go shorter or longer? Thanks!

[Timx]

Google , fan belt 860, for a multitude of choices,I just did and loads came up.

[jhoff]

Cheers Tim... I did Google it and am looking on various other sites, but couldn't see any at the correct width so just enquiring for some general advice about length etc.

[alan_fincher]

860mm sounds very short for a belt on a BMC 1.8. I feel fairly sure.they are normally well over a metre. Is this driving both a pump and an alternator, because I can't see how it could be long enough.

[jhoff]

I have one for the alternator which is 1225 and this one I think just drives the cooling pump. Definitely is Powertrain 860.

[alan_fincher]

3 hours ago, jhoff said:

I have one for the alternator which is 1225 and this one I think just drives the cooling pump. Definitely is Powertrain 860.

Is this an engine that has two cooling pumps - the engine mounted one, and maybe a separate "Jabsco" type pump?

Is it skin tank cooled, or by water taken from the cut?

Either way your shorter belt is not normally found on such engines in canal use, so hard for anybody to advise without knowing width, profile and how much scope you have in terms of adjustment for using a slightly different length.  It always surprises me that really very small differences in the size can mean that one belt fits easily, and the next size in either direction can't necessarily be made to.

Edited March 20, 2018 by alan_fincher

[jhoff]

Water from the cut - and yes, this 860mm belt drives the Jabsco pump.

[alan_fincher]

1 minute ago, jhoff said:

Water from the cut - and yes, this 860mm belt drives the Jabsco pump.

OK, understand now.  I don't think such an arrangement is particularly standard, so advice from someone else who has something similar but not identical may not be much help.  Definitely need to ascertain width of existing belt and pulleys.  I have never found much difference between belts claimed to be (for example) 9.5mm & 10mm, but you certainly couldn't use (say) the next width up (probably 12.5mm/13mm, from memory), for pulleys designed for the smaller size.  (Or vice versa.....)

[jhoff]

Okay, brilliant, thanks a lot Alan - I have found one that is 0.3mm out so I would imagine that'd do fine. Thanks for the advice and reassurance! Much appreciated

[Tony Brooks]

And for raw water pumps its probably best to run the belt a bit slack because not all such pumps have proper bearings, a tight belt running a pump with the  bronze body forming the bearing may well wear rather fast. The load on the belt is very low so you will probably not notice any difference if you get one of technically the wrong profile - as long a it fits the pulleys.

[jhoff]

Okay great - I did err on the side of slightly longer when purchasing, so that is good to know, thanks Tony.