Difference between all Z Engine Blocks?

[brian_73Z]

Ok, I know the differences between the l24, l26 and l28 engines when it comes to the bore and the stroke. But what I want to know is if there are any differences between the blocks themselves. My understanding is that the blocks before being bored and sleeved are all identical.

In other words, I should be able to take a P30 and convert it to an F54 if I had access to a machine shop and money wasn't an option. Right?

My second question assumes that the l24 to l28 conversion is possible and if it is then I should also be able to convert it to a 3.1L displacement like they do at Rebello Racing. I realize that the block may need to be resleeved to accomplish this, but I am just wondering if it is physically possible.

[Walter Moore]

Rebello makes a 2.7L "stroker" out of the L24. I presume that if it was possible to take it to 3.1L they would, and they don't.

The oft repeated story is that the L28E is the only block that makes a good 3.xL stroker because the pistons are Siamese, that is they are connected to each other for strength.

I suspect that the cylinder walls of the L24 are not thick enough to bore them out to the 2.8L diameter. Yes you could sleeve the block bigger, but that might weaken the block to the point that it would not survive the extra torque. In the end it would be cheaper, and safer to use the L28E block in the first place.

[Diseazd]

Walter.....You are right....the L24 bored more than .080 will have trouble with ring seal due to cylinder wall flexing according to the old "How to Modify" book. If you want a big bore L24, your best bet is an L28 block with L24 crank, L24 rods and L28 pistons (same pin height as the L24). If you want to build a 3.1 stroker , you'll need an L28 block.....preferredly the F54.

Edited June 6, 2010 by Diseazd

[rjracin240]

If you want a big bore L24, your best bet is an L28 block with L24 crank, L24 rods and L28 pistons (same pin height as the L24).

Not sure if you could consider this a big bore L24 since you are using a L28 block, symantics put aside what displacement do you wind up with in this combination???

Someone also mentioned a 2.7 from a L24 block, what combination would you use to achieve that displacement??

Have been told that my current motor is a L24 with 280 rods and crank, which I am lead to believe is a displacement of 2.6?

Thanks for the help

[Zs-ondabrain]

So in that case, would the 4 cylinders be the same? I was always told this.........

L16 = 1.6 liter standard pistons and stroke

L18 = 1.8 liter with larger pistons but same stroke as L16

L20B= 2.0 liter with large pistons of 1.8L but longer stroke.

Would this be correct? and if so, do the 2.4 / 2.6 / 2.8 use the same principle?

just wondering.

Dave

[Diseazd]

Russ.....The L28 rods are 130.2mm center to center as are the L26 rods......they have the same Nissan part #'s therefore are the same. The cranks are also the same for the L26 and the L28 (each have the same 79mm stroke) and are therefore the same. What you have with an L24 block and an L28 crank and rods is an L26. The displacement on the the L28 block with L24 crank and rods and L28 pistons is 2575 cc's, or if you bore it out .040" you get a displacement of 2636 cc's ( I'm quoting OZCONNECTION on those numbers). Re the 2.7L Rebello.........I assume he's using the same Diesel crank that they use in the 3.1 stroker.....don't know what rods and pistons Dave uses for that build. Guy

Edited June 6, 2010 by Diseazd

[Walter Moore]

The bore of the L26 is the same as the L24, and the stroke of the L26 is the same as the L28, so if you have an L24 with the L28 rods and crank you have an L26.

(More or less depending upon if the head has been opened up enough to breath correctly.)

[Carl Beck]

Ok, I know the differences between the l24, l26 and l28 engines when it comes to the bore and the stroke. But what I want to know is if there are any differences between the blocks themselves. My understanding is that the blocks before being bored and sleeved are all identical.

The L24 and later L26 blocks were the basic same castings - Except, the L26 blocks had eyebrows machined in them to clear the larger valves use in the L26.

The L28 blocks were a different casting. The cylinder walls are cast with a larger diameter to begin with. The second casting of the L28's put additional webbing between pairs of cylinder bores - some reports say that this was done to strengthen the cylinder bores, others say it was actually done to redirect the coolant flow inside the block for increased cooling for the turbo heads..

In other words, I should be able to take a P30 and convert it to an F54 if I had access to a machine shop and money wasn't an option. Right?

Convert it - Not really. I suppose you could cut the P30 open, then cut the cylinder bores out of an L28 and weld them in.. along with the webbing between them... but seriously - NO.

My second question assumes that the l24 to l28 conversion is possible and if it is then I should also be able to convert it to a 3.1L displacement like they do at Rebello Racing. I realize that the block may need to be resleeved to accomplish this, but I am just wondering if it is physically possible.

You can't "re-sleeve" a block that wasn't designed/cast to use replaceable cylinder sleeves to begin with. If you had a cylinder sleeve, the diameter of a bored out L28 cylinder - and you cut the entire L24 cylinder wall out to make room for it - you still would have nothing to hold the bottom of the replacement cylinder bore and/or its sleeve in {ie...keep it from dropping down on the crank below}.

A better approach - grind the "L28" off an L28 block and re-stamp it "L24". Then grind the casting numbers off the side of the block, and weld in the L24 casting numbers. :-)

FWIW,

Carl B.

[TomoHawk]

V-8 engines have features like 2-bolt main bearing, 4-bolt main bearings, webbed reinforcement of the cylinders, more oil return passages, etc. Is there anything like that in any of the L24/L26/L28 engines to make certain ones desirable?

[ozconnection]

Russ.....The L28 rods are 130.2mm center to center as are the L26 rods......they have the same Nissan part #'s therefore are the same. The cranks are also the same for the L26 and the L28 (each have the same 79mm stroke) and are therefore the same. What you have with an L24 block and an L28 crank and rods is an L26. The displacement on the the L28 block with L24 crank and rods and L28 pistons is 2575 cc's, or if you bore it out .040" you get a displacement of 2636 cc's ( I'm quoting OZCONNECTION on those numbers). Re the 2.7L Rebello.........I assume he's using the same Diesel crank that they use in the 3.1 stroker.....don't know what rods and pistons Dave uses for that build. Guy

Those numbers are spot on Guy! Thanks for the achnowledgement! :classic:

[brian_73Z]

Thanks for the responses guys. Seems you all have quite a bit of knowledge in regards to these engines. I was considering several different ideas for my 73 240z rebuild/restore project including RB26DET, LS6 and 2JZ engine swaps. But I think I have decided to just keep it pretty much stock. I will go through the engine and maybe do some head work, put in a more aggresive cam and maybe larger valves, but thats about all. I am also planning to upgrade a few things like the distributer, ignition and things like that. Should be fun, but will probably take me awhile to get it all done. I finally have the car down to the shell and it will be going out to be soda blasted sometime in the next few weeks. I will start the engine teardown while the body is away getting worked on.

[HS30-H]

The second casting of the L28's put additional webbing between pairs of cylinder bores - some reports say that this was done to strengthen the cylinder bores, others say it was actually done to redirect the coolant flow inside the block for increased cooling for the turbo heads..

Carl,

I think you have got this N42 and F54 block internals thing the wrong way round....

The N42 block casting ( the earlier of the two ) had more 'meat' between the bores than the F54 block casting that followed it.

The F54 block casting had 'siamesed' cooling passages between the bores - ie less 'meat' - which actually makes it less stiff than the N42 casting.

When going for maximum bore on an L28 block, the N42 has often been chosen because the extra material in the block casting leaves greater wall thickness, which helps to keep bores round in use.

In contrast, the F54 block has often been chosen because people misunderstand what 'siamesed cooling passages' means. They think that they are "stronger", when in fact they simply have better cooling properties. The F54 has less internal structure than the N42.

And amongst tuners in Japan, the earliest N42 block castings were always reputed to have 'better' metallurgy than the later F54s.

Alan T.