970S race water pump

[Rusty old S]

I have just started recommissioning a time warp 970 racer, not run for possibly 40 years it’s full Longman spec/ jack knight . Pulled off head then water pump as seized but to my surprise it is a shallow impeller type with a screw on the body for lube hole. It’s the same colour blue like the rest of unit so it’s been on along time. My question. Was this fitted for a reason of lowering drag/ reducing cavitation bearing in mind they rev to 9K or more or just fit deep impeller type

[AndyPen]

Hiya,

Can't say for 100 per cent certain but funnily enough, our 970 racer had a shallow impeller type pump. I fitted a deep one but don't race it to test its effectiveness.

[mk1]

When running at such high rpm it "may" make sense, but I suspect that cavitation wouldn't be reduced "that" much as the impeller is still spinning at a heck of a rate.

Another possible reason could be to reduce the drag from the water pump to make sure as much power gets to the wheels as possible.

[Rusty old S]

Yes Mark , that what I thought but as it will never be used in anger so normal pimp will be fitted and try to get it I assembled for for Blyton (not for track) just a runner/ display. Peter

[dutchacme]

what size pulley was fitted ?

[Rusty old S]

Small pulley as 850 , Larger 1275 Pulley rubs the head

[dutchacme]

To reduce the water pump speed even more a cut-out can be made in the underside of the thermostat housing accommodating a larger pulley, about one millimetre gap is sufficient. Assembly has to be with the belt around the pulley.

A 970 can rev to 9000 rpm however the torque falls down considerably after 7500 rpm due to the restricted breathing of a five porter. Better to tune for torque band and stay in the torque band and shift typically around 7500 rpm with an 649.