Modifying a 1983 280ZX Turbo F54 engine

[Guest ZSource]

I have a 1983 280ZX Turbo engine and an early 240Z E31 head and distributor. All three are in excellent condition. Can I merely swap the Turbo's P90A head for the E31 and the electronic ignition distributor for the 240Z model? I want to add carburetors and drop the slightly modified engine into a 240Z. If there's more to it, I'd like to know before I'm in the middle of the swap.

[JMortensen]

Putting the E31 on a block with dished pistons yields an 8.56:1 compression ratio, and makes the quench area almost nil. Not exactly high performance oriented. Flat tops make about 10.2:1. Bore .40 over and you get 10.5:1 approximately.

 

This is with a standard thickness head gasket. If you use a 2mm head gasket, your quench area will also be useless, because the pistons and head need to be within .045 or so to make effective quench, but your compression drops to 9.63:1.

 

All of these compression ratios were figured using the Nissan L6 Engine Builder program which I got from an internet site. I tried the URL they list, and it is no longer there, but its a useful program if you can find it. I can't remember which other Z site I saw it on recently.

 

FWIW, I have a F54 flat top block and E31 with 44 Mikunis, and I have had problems running pump gas. I had to run very little advance with 92 octane, and that is not good because it puts a lot of heat into the exhaust manifold and exhaust valves, and the motor made no power and wouldn't rev. I have figured out that I need about 96 octane to stop pinging, and so I've been cutting my fuel with Tolulene, 5 gallons gas and 1 gallon Tolulene, or lately been running 1/2 92 octane, 1/2 100 octane leaded AVgas, which is very illegal on the street. Tolulene is about $10/gal from the paint supply store, and is 114 octane. It is a very strong solvent, and it is already in the gas you get from the pump, and is also usually the main ingredient in most octane boosters (which are a serious ripoff BTW). From what I've read, you can run up to 30% tolulene (aka toluol) with no ill effects. I've had no problems so far.

 

My first motor was a dished L28 block bored .020 over and supposedly had dished pistons that were only 1/2 as deep as the standard dish. Since I had that motor built I found that the machinist who ordered the pistons was a complete hack and totally screwed me on the buildup, so I now think that they were your usual dished pistons and I was running 8.5 compression. It was a good motor, and I could run 87 in it all day long.

 

With 96 octane, flat tops, and the timing appropriately advanced the car is pretty damn fast, much more so than the old motor.

 

Jon

[JMortensen]

One more thing, I am 99.99999% sure you need an N/A distributor. I've bought a couple from the junkyard now for ~$50 with the module. You can use the stock module or run MSD.

 

Jon

[Sean73]

I don't think you'll realize any performance gain over a stock L28. In fact, you may lose power compared to the stock L28 unless you seriously modify the E31, or change pistons. Also, you can't judge the condition of a cylinder head just on appearance. The valve guides, seats, seals, and springs all will need thorough inspection. It would cost a minimum of 400 at a machine shop to have the head checked out and refurbished to OEM specs.

 

The L28ET block and dished pistons aren't suitable for an NA application. Your better off installing the L28ET and getting a turbo wiring harness, ECU , AFM & other EFI accessories needed for the turbo swap. Alternatively, get flattop pistons and use the P90 head - that would be a decent combo, but more or less stock.