hey i have a 71. the engine was out when i got it but it came with the car. but i donno what size it is . can someone clue me in how what is the difference?

i know this is a dumb q for you guys im all full of em .

Should be an L24 - 2400cc.

If you look at the right side of the block at the top back, there should be two flat places, one with a four digit number, and one that says L24. If it says something other than L24, it could be L26 or L28, which would mean a block from a 260Z or 280Z, at 2600cc or 2800cc. These values are all rounded up slightly.

Oh, and I think the L24 and L26 blocks are the same, and the extra displacement achieved through a change in the stroke - right engine experts?

In fact the L24, L26 and L28 blocks are all the "same" (minor differences externally). the extra displacement comes from increasing the stroke (L24 to L26) and increasing the bore (L26 to L28).

Originally posted by halz

In fact the L24, L26 and L28 blocks are all the "same" (minor differences externally). the extra displacement comes from increasing the stroke (L24 to L26) and increasing the bore (L26 to L28).

Well, that's true, but I was just trying to make the point that without the L24 or L26 marking, you wouldn't be able to tell them apart because the bore was the same. The L28 bore makes it at least distinguishable from the other two. And I've never actualy had a 260Z, so I'm only assuming it says L26 on the block . Of course, of you bored out the L24 block, then it would be the same as the L28, right? Except I gather that isn't a good idea...I assume due to internal wall thicknesses and webbing being different.

so I'm only assuming it says L26 on the block

It does!

I think you could overbore an L24 to fit L28 pistons. Only the later L28 blocks had the extra webbing in the casting and I think that was the cope with the loads of a turbo engine..(?)

Originally posted by halz

Only the later L28 blocks had the extra webbing in the casting and I think that was the cope with the loads of a turbo engine..(?)

Is that the F54 block that I hear about from some of the power-makers? Or is that something different :cross-eye ?

Originally posted by mdbrandy

Is that the F54 block that I hear about from some of the power-makers? Or is that something different :cross-eye ?

Yes, that would be the F54 block.

cool thanks guys.

F-54 is the block from the ZX series cars. Still a 280 but the casting is enternally different , just the way the cylinders were supported has nothing to do with displacement. These are the latest evolution of the inline 6. I n boring a L-24 out to the larger pistons the side wall can get thin.

I n boring a L-24 out to the larger pistons the side wall can get thin.

Well I wouldn't expect them to get thicker

What about the L28 in a 280Z... are its liners thinner than in a 240Z?