3 Hole & 2 Hole Fuel pumps

[Zedrally]

Hi all,

The puzzling oil leak from the fuel pump has opened up a couple of interesting questions, as to the geneology of the engine blocks of the L24 & L26.

Seeking technical guidence, I made some comparisions with the FSM of the 330 series [known as the 260C in Australia].

The fuel pump in this is still an EDP [engine driven pump], which surprised me as all 260Z's here came with an electrical pump. Bit retro maybe as Nissan may have had an over abundance of EDP's and this series didn't suffer from vapour lock

The surprising "find" was that it was actually a 2 hole bolt on EDP, whereas the 240Z was a 3 hole. [When inquiring about a new pump, I was asked if it was 2 or 3 hole, which made me think it was for a L series below L18]. My 260Z has a 3 hole blanking plate here.

Now this makes it appear that there is a difference in the Block, even though they are to all intents and purposes they are the same.

The technical diagrams make the 2 hole pump not as "high" as the 3 bolt, [more squat] which would mean that there is a difference in blocks!

Can anyone confirm that there are in fact different blocks in the L26 series

[Bambikiller240]

The technical diagrams make the 2 hole pump not as "high" as the 3 bolt, [more squat] which would mean that there is a difference in blocks!

I don't understand how the difference in height of pumps means there is (or could be) different blocks?

[Zedrally]

The 2 holes on the horizontal are at similar heights on the block.

It is the lower or 3rd hole which makes the EDP "taller/higher".

As an example [but not actual], take the 2 hole pump to cover a surface area of 50*50 [a square], whike the 3 hole pump is 50*75 [oblong].

The corresponding hole in the block must be similar.

Another way of describing this might be that while the 2 hole pump will bolt on the 3 hole block, it does however leave a gap of "x" amount open to the atmosphere.

[Bambikiller240]

Yes. but remember the fumps mount on the HEAD. IMO, the hole in the head (for the actuator arm of the pump) is simply milled to a different size for applications using one or the other pump. No reason for the "BLOCK" to be any different. Why the difference,.......I don't know. Curious just like you.

At least, that's the way I see it.

[Zedrally]

OMG, Your absolutely correct.

The pump does mount on the head, not the block.

So I will now rephrase this as different L26 Heads.

[Bambikiller240]

Engines with similar displacement and design, making similar HP *should* (in therory) have similar fuel requirements so I would think that both pumps are likely to "pump" the same volume. Unless, maybe the 260C has a lower HP version of the L26? What casting # is on the 260C head?

Perhaps the supplier of pumps to Nissan changed the mounting plate design for some reason. It would seem to me that the 3 hole mount would be more sturdy than the 2 hole mount.