smaller waterpump pulley for 355/456/550/575

That might work or make cooling worse if the higher pump RPM cavitates insteads of increases flow. I think a good person to ping is cribbj He is an engineer and experimented with this on a 550 and knows more about the math.

 

It's hard to imagine needing more water pump speed. If you are having trouble with cooling, there are a few more likely causes.

A smaller pulley would need to be custom made.

 

There are products on the market that promise a cooler running engine, kind of additives for the water.

 

Your standard water pump pulley (P/N: 166454) is 102mm in diameter.

The 575 pulley (P/N: 169924) is a 93mm pulley - this will increase the pump flow, however higher flow at high RPM may push the pump outside its design range, and also produce cavitation, so be careful.....
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Like FBB stated, very possible that cavitation will occur with the smaller pulley. I upgraded to a 575 shroud for insurance...

 

I would look into electric waterpumps. They are much more efficient at temp control and have an added benefit of a gain in HP, due no belt driven impellor and no thermostat restriction to water flow
The pump controller manages fans as well and the system can be programed to run after shutdown, and unlike mecahnical pumps there is a teltail wairng light if the system fails before it boils.

 

The 550 belt will still work, although it could stand to be a couple mm shorter.

 

Here is something that does not have counter indications.
Recently I had the car in the shop to change the brake pads and once on the lift it looked like there could be also a small leak from the radiator (which in the end there wasn't).
Once the radiator was out I decided to do something I had been mulling about for a while and replaced the stock fans with new SPAL hi performance ones.
Part # SPU-IX-30102029 for the 12" and SPU-IX-30102049 for the 16".
SPAL was very helpful to identify the correct parts for me, but they do not sell to private individuals, so I bought them from Summit Racing, a distributor.
The difference is in the shape of the blades: the new ones are curved, while the old ones are straight.
They are a perfect fit, requiring no modification whatsoever and when running, gone is the dual electric blender noise.
For now cooling temperature is lower than before, but since we are not in the peak of the Summer yet, I reserve the final judgment for July or August.

 

Great info this may be worth putting in the 456 550 575 replacement parts list.

 

oss117,
many thanks for the fan info.
Fans now ordered.

 

A change in water pump pullies is not going to cure your cooling system issues. Get the car checked properly.

 

Since I have a 550, I decided to try its belt and it fit OK, although ideally it should have been a bit shorter as the tensioner was nearly at its limit.