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I have recently aquired an ER27 Oil Pump & Water Pump, after finding out that they are higher volume items... here are the comparative photos:

I managed to source a brand new ACE branded japanese pump from global spares, the oil pump I had to import from the states.

As you will see below, the rotors on the ER pump are 5mm wider than the EA pump, but the housing has been machined from where the O ring groove is, out, so that the pump fits in the same size 'hole' in the engine block

The ER apparently uses a wider T belt, as the pulley is wider, hopefully I can fit the EA pulley, the pump shaft though is larger in diameter, have to see about that...

The gasket is a different shape than the EA pump, due to an oil gallery beside the rotor

Only other difference I found so far is one of the Timing Cover mounting threads is in a slightly different position

...As for the water pump, first of all the ER inlet is a whopping 42mm, rather than the piddly 32mm EA one!

The 'height' of the pump is the same as the RX pump, 10mm higher than the XT pump,

The main difference is the heater barb, which comes off at a completely different angle, which I should be able to manage as I do not have AirCon...Not sure about the XT's timing plate though, which bolts on to those 2 threads where that barb is...

Also, one of the timing cover threads is in a slightly different place, and the casting where the case sits under the pump is a slightly different shape...

(reserved for photos trying to fit the oil pump)

For now - the comparative specs:

(reserved for photos trying to fit the water pump)

For now - the comparative specs:

good find on the oil pump! (if it fits)

Yes im very impressed. Why has nobody noticed this before?

Its understanding that the ER27 has a bigger oil pump, as it has 1.5 times as much engine to lubricate. But i have never heard of an EA82T failing because of insufficient oil pressure or flow. You dont want to have too much oil flow/pressure

As for the waterpump, this could help force more water through the galleries in the heads and have a positive effect on keeping your head and headgasket intact.

Cant wait to see if they fit

Ah, but - Neville was also investigating oil cooler fitment a while back. He IS up to something....

The pump differences have been mentioned in the past on USMB .

My thoughts are 82 pumps for 82's and ER27 pumps for ER27's .
Even if you could make the six cylinder pumps fit and work what will they achieve on an EA82 ?

I don't think I've ever heard of an EA82/T failing because of lack of oil pump capacity . I don't see any reason why you couldn't add an oil cooler with the std oil pump , oil coolers themselves don't create a pump capacity problem .
This I remember reading ages ago about another production engine but the principles don't change .
Once you get beyond adequate oil pump capacity all that happens is that the pressure relief valve opens further to dump the excess oil back to the sump .
Oil pumps take crank power to drive so larger capacity pumps are a greater parasitic power loss .

Water pumps , yes you can have too much capacity .
Obviously the water passages are larger in a 27 than they are in an 82 , I'm pretty sure the radiator hose barbs are larger in an XT6's rad than an XT4 or L Series .
Don't forget that an ER27 is 50% larger in capacity than an EA82 and in theory can generate 50% more heat for the cooling system to reject . I'd be concerned that the higher capacity water pump may not be able to force coolant through an 82's modestly sized coolant passages , if it creates surge then the pump is a step backwards .

Your call but I would not have gone down that road , it will introduce the need for custom mods and the modified 82 may not then take std pumps afterwards . Also what happens if you damage ER27 pumps and cannot get them at short notice .

A .

there are two different water pumps for the ea82, the difference is the length of the shaft, measured from the flat back of the body to the flat front of the fan pulley the difference is about 6mm, this is enough to put the belt out of alignment. I found this out the hard way.