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4G63 Aluminium oversize water pump pulley

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Hi from France,

I'm building a high spec street/rally car Mitsubishi lancer Evo 8 and I'm hesitating to fit an aluminium oversize water pump pulley from Monster sport

Engine is fully build and balanced and I use a Fluidampr crank pulley. Max Rpm of the engine is 8500Rpm, it has a PWR oversize radiator, power steering and Air conditioning compressor.

Do you think it's good idea to increase water pump rotation ? The car is not a full race car, it's drive on mountain pass and run in traffic usually, and can be stuck in traffic jam at idle at 40°C exterior temp at summer.

What about the wear with aluminium compare to OEM ? (Monster sport product are top quality materials, not crap Ebay pulley...)

What about the balancing of the water pump unit compare to OEM ?

Thanks for your feedbacks ;-)


Hello Victor

There is no issue with the standard pulley, they do not have a over heating issue at all caused by the standard size pulley.

The balance of the alloy one if you do decide to fit is not and issue the oem one is not balanced either, The alloy one will be more likely to be closer to zero balance than a pressed steel one, so no problem if you did want to use it

Regards Ross

Uh, you're both missing the point - a larger WATER PUMP pulley will slow down the water pump, not speed it up.

They're to reduce parasitic power losses and/or reduce cavitation at high rpm when reducing pump speed isn't a problem as it is still enough for good circulation.

A SMALLER pump pulley will increase pump speed, which may be helpful if driving slowly, under load, in extreme conditions.

As you already have an upgraded radiator, I would try it and see if it caused an issue - just check alignment carefully.

Thanks for your support ;)

+1 voice to Gord. I tried a set of aftermarket pulleys from Tomei and did not like it - the alternator did not provide proper voltage, crankshaft pulley was to light resulting in conrod bearings wearing out. It is purely for sports applications where they want to reduce rotating mass as much as they can. I would not try it on a regular street car - it just not worth it although the engine revs quicker...

Georg, for a crank pulley I agree, this was for a water pump pulley - yeah, had to read it twice too.

Yes, i noticed that. I just wanted to highlight the point that lightweight pulleys are for sports rather than for street vehicles...