Simply because I had all the parts handy, I took fresh measurements and ran some numbers:

280 throttle butterfly - 50mm diameter. This provides 1964 mm square area. The Sentra (96-98) throttle body as well as the 280ZX are also the same as the 280Z

Carbs butterfly (both round and flat tops) - 46mm diameter. This provides 1662 mm square area.

Now interesting (to me) is that the 1964 sq mm for the throttle body is shared between six cylinders, while the 1662 sq mm for the carbs is shared only between three cylinders instead of six.

So for the fuel injection, it works out to 327 sq mm per cylinder and the carbs work out to 554 sq mm per cylinder. The carbs provide significantly more butterfly area per cylinder than the fuel injection. Now I'm sure Nissan did their research and found 50mm diameter for the EFI was good enough, but the difference is still striking.

Working backwards from the carbs 554 sq mm per cylinder, you would need a 65mm diameter throttle body to get the equivalent area per cylinder.

I'm no in any position to draw any conclusions from the above, but I was moving some stuff around today and had all the parts handy at the same time.  

On 11/1/2020 at 2:09 PM, conedodger said:

Anyone have one of the factory heat shields for the brake aperatus that bolts to the bottom of the heat shield? I might as I have had a couple 280Z cars over the years as well but I'm no where near my parts garage...

I am pretty sure I have one available, I picked up some 280Z parts a while back. I will confirm this afternoon when I am home from work. 

5 hours ago, Terrapin Z said:

I am pretty sure I have one available, I picked up some 280Z parts a while back. I will confirm this afternoon when I am home from work. 

 David! We're on a roll! 

I have an F54 block. Anyone know where the knock sensor went? I’m thinking I might be able to hook up a modern knock sensor to the Haltech ecu.

Here’s a couple pics off my 83zxt engine I bought. Haven’t verified it but this might be it.

Mine must not be a turbo block then. I don't have that. 

6 hours ago, conedodger said:

 David! We're on a roll! 

Ha ha, we should have put together some kind of parts swap. 

These are three of the shield I have loose. I am not sure which one you are looking for. The small one looks like it bolts to the bottom of the EFI manifold. It is in the parts schematic #11 I think it was a shield for the AFM.

I thought the bigger curved one went around the Master cylinder. I'm not real sure about the square one. I could not find either of these in the car parts manual on line. 

Let me know if any of these are the ones you are looking for. 

Nice David. Got a price in mind? Take it to the private message if you want.

Is it possible to scream in exasperation on here? It's very frustrating. I want to use this supposedly 350Z eThrottle body. It is 75mm at the inlet side and 70mm at the outlet side. The 75mm inlet measure is what makes me wonder if it is really a 350Z TB. If you go to YouTube, all of the videos on the throttle body are about upgrading to the 75mm throttle body. I'm guessing, either I have something other than a 350Z throttle body or the stated size refers to the engine side of the throttle body.

Anyway, the problem is, I intend to use the stock '75 intake manifold and I need to figure a way to mount it. All of the machine shops I have talked to (3) don't want to bother with a job this small. Bummer!

When they are stating the size of a throttle body, they use the diameter of the butterfly. And usually, the outlet size is the same size as the butterfly, so that would make that a 70mm throttle body regardless of the larger diameter inlet side.

Now, I have no idea if that throttle body you have there is the same as the factory supplied throttle bodies for the 350Z, but that one you have there would be called a 70mm.

As for the mounting... Did your son make up drawings for an adapter?

2 hours ago, Captain Obvious said:

When they are stating the size of a throttle body, they use the diameter of the butterfly. And usually, the outlet size is the same size as the butterfly, so that would make that a 70mm throttle body regardless of the larger diameter inlet side.

Now, I have no idea if that throttle body you have there is the same as the factory supplied throttle bodies for the 350Z, but that one you have there would be called a 70mm.

As for the mounting... Did your son make up drawings for an adapter?

Yes. That’s what I’ve been circulating to the machine shops with...

Can you post the drawing?  Maybe one of us can help.