During the 8 year run of the S30 chassis there were a few major engine changes made. First is the size change from 2393cc to 2565cc in 1974 and then in the US market the engine changed again to 2753cc. Here we will talk about the Block, Cylinder head, Crank and piston differences.
*WARNING* - Do this diagnosis/mods at your own risk. We Are not responsable for any issues of your own doing.
The way to identify the block is to look on the driver side of the engine. To the right of the motor mount is where the block number is cast. The chart below will also help you in identifying your block.
| Engine and Years | Displacement | Casting Code | Bore | Notes |
|---|---|---|---|---|
| L24 (1970) 240Z | 2393cc | E31 | 83.0mm | ? |
| L24 (1971-1973) 240Z | 2393cc | P30 | 83.0mm | ? |
| L26 (1974) 260Z | 2565cc | P30 | 83.0mm | Used the 79.0mm stroke crank |
| L28 (1975-1980) 280Z 280ZX | 2753cc | N42 | 86.0mm | First EFI L-series in the US |
| L28 (1981-1983) 280ZX | 2753cc | F54 | 86.0mm |
Cylinders are "siamesed" Cast webbing for more rigidity |
The L-series had six different heads used on the different blocks. Here, we’ll chart the differences between the heads and how to identify them.
To identify these heads, look at the head number cast between the 1st and 2nd spark plug holes.
| Years and Models | Casting | Compression Ratio | Chamber CC | Notes |
|---|---|---|---|---|
| 1970 240Z E31 Block | E31 | 9.13:1 | 42.4cc | Uncommon, desirable head that came on many 1970 240's. It's chambers were high-quench designs, however the valves were smaller than the 260 and 280 heads. |
| 1971-1973 240Z and 1974 260Z P30 Block | E88 |
8.76:1 240Z 8.26:1 260Z Dished pistons 9.24:1 260Z flat top pistons |
44.7cc | 2 versions were available, a small valve on the 240Z and larger valve on the 260Z. |
| 1975-1976 280Z N42 Block | N42 | 8.29:1 | 44.6cc | The larger valve N42 came on the 1975-76 280Z. 48-state U.S. 280Zs didn't use a catalytic converter until 1977, so the head came with softer brass valve seats for use with leaded gas. Many people like these for performance because of its square exhaust ports. As an easy mod, putting it on a flattop L28 motor puts compression in the mid 10's. |
| 1978-1980 280Z/ZX N42 Block | N47 | 8.29:1 | 44.6cc | Has diamond-shaped exhaust ports with emission liners, which some feel reduce flow. Starting in 1977 Nissan heads came with steel seats for use with unleaded gas. Like the N42, putting it on a flattop L28 motor puts compression in the mid 10's. |
| 1981-1983 280ZX Non Turbo F54 Block | P79 | 8.82:1 | 53.6cc | Came on 81-83 flattop piston L28 (F54) blocks. It has a 53cc chamber and must be used with flattop pistons or compression drops to 7.8:1 (with dished pistons). The exhaust ports/liners are identical to the N47, and used an internally oiled cam. |
| 1981-early 1983 280ZX Turbo F54 Block | P90 | 7.38:1 | 53.6cc | It has the same combustion chambers as the P79, but has square exhaust ports like the N42. The P90 and P90a are said to be the best flowing heads due to their turbo origins. They both use an internally oiled cam. |
| Late 1983 280ZX Turbo F54 Block | P90a | 7.38:1 | 53.6cc | Hydraulic lifter head, but many of the heads were in fact equipped with solid lifters. Usually these heads were models created earlier in the production year. |
Like the heads and blocks, there were many different pistons used in the L Series engines. All pistons were cast aluminum with two compression rings and one oil ring.
The main difference between pistons in the L series is whether they are flat top or dished. The following chart will show you what pistons came in what car and block.
| Model | Bore | Wrist Pin Height | Pin Diameter | Dish/Dome |
|---|---|---|---|---|
| L24 E31 and P30 Block 1970-1973 | 83mm | 38.1mm | 21mm | 0 Flat top |
| L26 Early P30 Block 1974 | 83mm | 38.1mm | 21mm | 0 Flat top |
| L26 Late P30 Block 1974 | 83mm | 38.1mm | 21mm | -7.01cc Dish |
| L28 Early N42 Block 1975-1980 | 86mm | 38.1mm | 21mm | -10.9cc Dish |
| L28 Late Non Turbo F54 Block 1981-1983 | 86mm | 38.1mm | 21mm | 0 Flat top |
| L28 Late Turbo F54 Block 1981-1983 | 86mm | 38.1mm | 21mm | -10.9cc Dish |
