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Water pump pulley size


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My SofS Vitesse overheats on the track.  Not on the road or on motorways, even in hot weather.
One factor could be that at high revs, the pump is cavitating.

If I could use a larger pulley on the pump, it would be driven slower, and be less likely to cavitate.
   I believe that there was some variation in pulley size in Triumph pumps.
Can anyone tell me which sizes and which cars, please?


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Me sell John, think yer bark,n up the wrong tree.

yer cars over heating, but no on the road,
but its dooing it on track,

thats got some thing to doo wid the ally rad you got, { ally dont get rid of heat as fast as copper, a known fact.AND, its got less cores too.
lack of any rad shroud
and  possibly a too small an oil cooler, 13 row,!!!
and too much WOT and high revs and low speeds.

there also the fact  you got a bung in yer  thermo housing,
I bet it aint bell mouthed, like a carb inlet,
{ye would,nt run a carb with oot a bell mouth noo would you, }
your loosing at least 5-8% in water flow there due to boundry layer restriction,.

As for a smaller pully, just hoo you no its cavitating,

there been lots of T 6 pots going alot moer revs than you, and they no over heated.
Did yer last engine over heat wid the olde OE rad init,!!!

Yer oil cooler has alott t,doo with how hot yer water is when yer going high revs low speed, as ye just cant get the air flow to cool it down as much as going flat out top speed.

this is the main reason I went to a bigg 19 row water cooler.
and now a 25 row one.

{ my oe water cooled 19 row rad would heat the water if used as on a track,
but never got water temp over 90degs or oil over 100  normals was about 80 for both, but give it 5.5 k in top for miles on end, the temps were stopping at 85 ish which shows its air flow that counts,}

first off, try running wid a thermostat, yes I no ye tek em oot , bung a bung in ..just incase it goes awol ina race, but this  bung aint helping.

then try and get some decent air flow thru the rad, IE, ALL air that comes in, thru the rad, no the top/sides/bottom

what size yer cooler, and wheres it at

air that come in, has gotta get oot,
its nee good getting it backing up inside engine bay,
Yes ye got vent in, but they too far forads. air press is not the same underneath the bonnet front to back, as I found oot yonks ago
neither is it the same at diff heights either.

also the pressure cap, is it  rated high enough,

As to a diff pully, as far as I no, they all the same, the 2.5s may look bigger,
got 2 in me shed, but the actuall bit that turns the belt is same size, its just the damper bit thats bigger.

never seen a pump with a bigger pully, just alternators, to slow them doon.

contructive advice John,  ok


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Very helpful, M!
The oil cooler is below the water radiator, facing the air flow beneath the front valance.  It's cowled, and behind, ducted downwards away from the under-bonnet.
I'm trying to do everything short of fitting a different radiator, again, hence the query about a different pulley.
Including fitting an electric water pump to back up the mechanical one, and thinking maybe I should put the thermostat back - it's not as if it takes as much time and trouble to do that as some of the other mods I've done.

As I've mentioned elsewhere, I went for the Civic rad as it was almost as big as the original and a third the price, when the costly repro rad had already proved to be poorly built when it can to racing.    What are you using, and dimensions, please?    The differences under the bonnet front of a GT6 and a Vitesse may not allow what fits the one to to fit the other.


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have you tried a water temp sender in the bottom hose between rad and pump?

if the water temp coming from the rad is the same or just below that which is going into the rad it is just not efficient enough at shedding heat.

also I think fitting an electric pump before the OE pump is a bad idea as it runs a lot slower than the OE pump does at high revs,the benefit of the electric one is that it is only on when needed whereas the OE pump is shifting a lot of coolant at high revs regardless if the engine needs it or not,but they say the electric one doesn't need a stat fitted.
I have one and have had no cooling issues at all apart from recently where I left my rad(second hand from a sierra cosworth) standing dry for a few years and I think the capillary tubes have furred up somewhat,i went for a blast on the a12 and when I slowed down the old temp gauge was almost off the scale.only slow driving would bring it back down and the fan came on for ages.
I tested the rad with the garden hose and it was flowing very little and pressurising.
I am now waiting for an all ally one from radtec,hopefully should restore the cooling back to normal.

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Pauls got some good valid points in thea John, esp about the  electric water pump

You did,nt say if yer olde rad was verheating the car, AND, olde engine if no mistek,n was a bigger engine.

my own rad is standard GT, but totally enclosed with large side flanges to direct air thru it
I understand you aint got that luxury though.

the only other thing is to fit a much bigger wider rad, but same height,
as a wider rad, but less thickness will dissapate heat better than a wider one,
as fins at rear aint been heated as much as if going thru moer cores like an OE.
yours got 3 core !!

think Steeve Povey fitted a wide rad to his, there some pics some where on here,
Steeve, piics for John pleeese.

My self, I have also got a multi vane impellor, and this seems to work fine.
noticed it was better at lower revs /town driving than OE 4 vane

maybe try trying to find one
But, id seriously consider a better rad, as yer probs stated with the rad you got., correct !!!

good luk

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[quote=796]Pauls got some good valid points in thea John, esp about the  electric water pump

think Steeve Povey fitted a wide rad to his, there some pics some where on here,
Steeve, piics for John pleeese.

Not sure if your confused or did mean me Marcus,i have an ally rad in my Vitesse 2.5,standard pump with a Spal fan.
I have a header tank which runs a feed to the thermo housing and back through the system as i was getting hot spots in the head.

Seems to work well but then i don`t go racing(not on a track)

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Hi John

Ive got the opposite problem that you have in that im always over cooling on the rally 2000. I fitted a racestorations alloy water pump and had the max number of cores put into the original early 2000 rad. I run with a thermostat and removed the fan altogether . I have a manual pusher fan. Which i only turn on if stationary for more than 5 mins or so. When moving the temp drops right off to approx 1/4 the heat from the heater matrix becomes luke warm. I can only get it reading on half/normal if its absolutely thrashed for competition. Been this way for over 40k now.

So you could try a racestorations alloy pump. Not cheap but works for me.

Cheers Dazzer

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