The V8 Owners Forum -

Hi guys, been a while, and not a V8 question (delete if you like Tony) but thought I stood a chance of some decent answers from you lot!

I am working on an engine at the moment and only need to drive the water pump, and am looking for as light weight and efficient setup as possible. I'd like to use a belt the perfect length over the crank and WP pulley, by bolting a pulley on with the belt already wrapped around it but the likelihood of finding a serp belt the perfect length and it not going loose by stretching is very slim.

If I use a belt almost the perfect length I assume I still need to use a tensioner pulley, which is killing my ideal solution. I suppose I'm best fabricating a very basic bracket with a pair of small bearings on and a roller, on the "slack" side of the belt unless someone has a genius idea I can use? Toothed may be an option but will need to play with sizes and custom make the pulleys and could I get away without a tensioner?

Only other option is to use an electric water pump, but I'm not sure if the reliability is there yet and this is a race engine so will require cooling at sustained high RPM's over a long time period.

Any help appreciated as usual!

Cheers,
TC

Hey TC long time no hear.

VW beetle air cooled v belt is what you want.
It tensions by pinching the pulley on the alt together thereby making the groove a larger diameter!

Clever those Germans!

Ian

The latest tech poly V belts on ancillary drives on mainstream cars are 'elastic/stretch' and run without tensioners of any kind. Whether there is one of an appropriate length for your need is a different question.

Stretch belt kits come with a small pressed metal device that allows the belt to mount itself to the pulleys while you wind the engine over on the crank bolt.

Hi Ian, after searching I see what you mean, I think that is how ride on mowers' variable drive speed works by combining the adjustable pulley with a centrifugal clutch which gears it up the more you rev it.

Good idea but too inefficient, I think other Ian posted that V belts are getting on for 10% less efficient than serp and toothed belts.

If I can find a stretch serp belt then that would be excellent! Will have a word with my local supplier.

Cheers

Here it is, I want to underdrive the water pump so there will be a change of pulleys involved, may be the perfect chance to find a stretch belt and make the pulley diameters to suit. Thanks again, after a bit of research the stretch serp belt looks ideal.