now that is getting fancy!

Not sure on the availability of that head in particular, but the B6 is common as muck. Thats a better option.
Plus Ill have to admit - if you make it suit that head, then it wont be any good to me! Arrgh.... Im neck deep in the B6 head setup.

However, that does sound very cool and fancy pants. VVT options and all.

looking forward to the revision.

Now that I have looked at it again - your right.

A custom pulley would have to be the only option.

Basically a square shape pulley that the belt could sit against might be enough.
Again, its only acting as an idler on the smooth side of the belt.
The steel of a custom pulley that bolts to the datsun pump wont wear out any time soon. The bush/bearing on the water pump might, but that would be easy to replace.

If you pull the pump forward to get the original v-belt groove to line up with the crank v-belt, then the impeller of the water pump will be out of the 'casing' (ie the block) and it may not work very well. The impeller needs a close casing to work else it just ends up like an outboard motor prop in the ocean.

This would then mean a fully remote option again with a backing plate on the datsun waterpump (to keep the impeller and casing close), and we are back to where we started.

Perhaps you can just machine off the v-belt bit off a standard pump pulley and see if it lines up close enough?

I reckon thats the go.

If you can put the standard water pump back - thats a win right there.

If you can design a bolt on adaptor between the standard water pump and an off the shelf idler, then thats (i think) the best solution. A full custom pulley would mean that replacing that becomes difficult when the bearing wears/fails. Not end of the world stuff, just a little harder to maintain is all.
But lets be honest, your not doing a DOHC setup cause its easy....

The standard v-belt pulley sits a fair way back (its offset back towards the block), so the end of the pump shaft would be close to where the timing belt would run.
I don't think you would need much of a spacer, if at all.

this image of the front of the engine shows how much the pulley is set back vs where the front of the shaft ends.

The more I think about it, and looking at the plate.

Could you cut off the adapter plate where the section that the original pump sits, and bolt the original pump back onto the block?
Then make up an adapter that bolts to the front of the standard 4 bolt flat face to extend it out and use a flat pulley/idler to get it to align with the timing belt. That would be a simple bush type adapter. Bolt the idler to the bush, then bolt the water pump to the adapter with 10mm bolts into the back of the bush.

As long as the area that covers over the original timing cover is sealed to prevent the oil coming out the rest of the plate is there to support the location of the tension and idler pulley.

That would make it much easier for parts moving forward, makes it more of a bolt together exercise.Just an adaptor for the front of the water pump.

Yeah I did D,

My concern with them is that they look too small to run as the primary pump.

They are listed as an Auxiliary pump, so Im unsure as to what function they are designed for in the VW design.
Unless you have all the technical specs, their intended use is the best guide as to how they will perform in an alternative environment.

Do you have any specs of these pumps? LPM output, duty cycle, max temp ratings etc
How many would you need?

To me they look like aquarium pumps and you would need a few to make it all work. One at the bottom radiator hose (to push into the block), one at the firewall for the heater (to ensure that it gets some), and one on the intake of the radiator (to suck from the motor)
Im happy to be wrong, but output from a centrifugal pump is a function of the size of the pump housing, so little pumps cant move much water. If you want more volume, spinning the pump faster only works so far, before cavatation sets in. You have to go to a bigger housing. Plus, since these are electric, their flow is set - what you get is what you get.

Also, its a bit hard to know exactly what the water volume requirements this motor will need. Most water pumps designed for a specific motor don't provide flow rates - its a mostly irrelevant fact as 'its deigned for the intended application'.

The Davis Craig EWP selection guide gives some hints. https://daviescraig.com.au/electric-water-pumps

They sell 'booster pumps' and replacement water pumps.

The booster pumps are designed for the extra water services, such as the heater, or an Air-water inter-cooler or such.

Their guide suggests that to replace a standard water pump for a standard 2l engine needs their 80 lpm unit, and for a modified / turbocharged engine their 150 lpm unit.

When I turbocharged my V8 diesel (I know its not directly comparable), I was surprised as to how much water it wanted. Now they are a hot engine with cooling issues as well, but I upgraded to an 80 gallon/min (300 lpm) unit, (biggest I could get), but the later versions of the same motor runs a 115gpm (435lpm)unit, and for modified motors thats still not enough.

I don't think that I need that much flow, the 150lpm unit will be heaps I think, but as I mentioned, those aux pumps just look too small to run on their own.

That sentra water pump looks like a good solution if it can be made to fit.

As long as the impeller can sit deep enough - that would be the thing to check. The plate is about 10mm thick from memory, so even if you cut out the right size hole, and impeller may not sit deep enough in the water travel way.

Perhaps, rather than bolting over the top, you recess the front of the plate down to say 5mm for the bolts and cut out enough for the impeller to sit in the water way.

Im still keen to use an electric water pump - for everything expect for race cars, and mega boost stuff it should be fine.
But I do like the idea to recess out the back of the plate to allow water to flow correctly as intended in the datsun block

Quote:

The B3 pulley does need to be machined out to suit the datsun crank snout, however it also needs to be spaced out to make everything line up.
Hence the bushing supplied with Robs kit.

Whilst I plan to use the mazda cam timing jigga(CAS) in the back of the head, I may need to move to a 36/1 trigger wheel. The mazda nuts do this for high revving engines as they complain about ignition betting 'scattered'. I may need to go down this path anyways for a couple of reasons. The CAS might not yet fit back there and the Delco ECM is eaiser to setup with a 36/1 toothed wheel.
That ZE/DE toothed wheel looks to be a good solution, however, aftermarket solutions are plentiful and eaiser to get
36/2 tooth ignition wheel

you will need at least

1 x Mazda DA 121 B3 crank pulley - needs to be machined out to suit datsun crank and use spacer busing to position correctly
1 x Dayco KI26 subaru 2.5l tensioner
1 x Subaru Forrester Nason NBT012 idler
1 x dayco T302/94616 timing belt Kia Spectra 2001-2004
1 x Mazda MX5 NB BP8 head timing pulley - used on the datsun camshaft with the adaptor.


The special adapter bushes for the crank and the datsun camshaft I am getting drawn up now. If you wait for them, ill send the image files as well.

To make it harder as well. The images of the plate on the motor are from Rob and are version 1. The drawing you have is at least version 2.

The drawings you have show that the idler on the right is already very low. There is nothing over the top of the water pump area except the timing belt. How much do you think you can machine out before it gets too thin?

My "shady-as-buggery" drawing shows the positions of the various pulleys as they stand now. The water pump area is already very clear, so machining out a gallery in that area on the back side facing the block should be no issue. (marked in red)

The holes are there to bolt to the existing studs/bolts that are there that normally would hold the standard water pump.

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