Help selecting a rod stroke ratio for a turbo build

[JMortensen]

1 fast z' date='

Are you saying that the f54 is not siamesed? Becuase that conflicts with all the published specs on these blocks (including manufacturer data, shop manuals, etc). Why would Nissan re-engineer their block to be WEAKER when they planned a turbo application? I've never cracked open an f54 myself, but maybe some of the turbo guys here could chime in.[/quote']

The F54 is definately as advertised with webbing about 1/2 way down the cylinder. Look down in a freeze plug hole and you'll see the webbing there. The question is whether that makes it a better block. This has been discussed here a couple times and John Coffey has said that the N42 block is a higher nickel content and has thicker walls IIRC. What it doesn't have is the brace 1/2 way down the cylinder.

[1 fast z]

Your right, it doesnt have the brace half way down the cylinder, it has it ALL the way down the cylinder.

[TheNeedForZ]

*sigh*....we need to cut open an N42 and and an F54 block to settle this once and for all. I went back to check the "how to modify" book and found something else : according to the "how to modify..." book, there are ***TWO*** types of turbo block.

 

"All L-series engines share the same basic block design except for that used in the 280ZX turbo. The ***FIRST*** L28 Turbo blocks have the front three and rear three cylinders Siamesed. Webs are cast between cylinders 1 and 2, 2 and 3, 4 and 5, and 5 and 6. Although this improved block rigidity, it was thought that the webs inhibited coolant flow around the Siamesed cylinders.

 

To improve coolant circulation, a casting change was made. On the L28 Turbo block 11010-P9080, introduced in the 280ZX Turbo in December, 1980, and non-turbo L28s in July 1981, ***SLOTS*** were put in the Siamesed cores to provide coolant passages between cylinders. Curiously enough, there were no incidents of piston-bore scuffing with the earlier L28 unslotted Siamesed blocks which would have indicated the need to use the later block for racing. However, the turbo block was used exclusively on Don Devendorf's Electramotive 600HP 280ZX Turbo L28. It was also used in Bob Sharp Racing 280ZX Turbo."

 

 

Is it possible that the "first turbo blocks" were actually N42 blocks? The book never used any block codes. Is it possible that the F54 blocks that we know as "turbo blocks", are in fact, later turbo blocks with extra "slots" in the webs?

 

If what the book said and what 1 fast z said are both true, then we can establish the following :

 

1. N42 blocks are siamesed throughout the length of the cylinder cores.

 

2. The earliest (prior to dec/80. But we know ZX Turbo was introduced in 81 therefore 'turbo blocks prior to dec/80' may sound like a paradox) turbo blocks might have been N42 blocks.

 

3. Turbo blocks after dec/80 (could be all the F54 out there?11010-P9080) do not have any "extra webs" but rather "extra slots" in the webs. What are the number, shape and location of the slots? Book never said anything.

 

4. If the earlier turbo blocks are indeed N42 blocks, then you can replace F54 with N42 without causing piston-bore scuffing at stock specs. Whether the N42 block will have problem at hi-performance spec is not known.

 

5. Don Devendorf and Bob Sharp Racing used F54 blocks for their racing. In Devendorf's case, the block supported 600hp without problem. Of course that doesn't mean a stock F54 bottom end can support 600hp.