76 280Z Throttle Body bolt spacing

[wheee!]

I'll go ahead and ask before CO does - is your ported port 70 mm across?  Doesn't look it.  70 mm would be outside the 60 mm centerline of the screw holes.  You'll need an adapter with a neck-down transition.  Kind of defeating the point.
They make a 60 mm big bore.  Looks like it would fit about perfect.
One example.  There's probably used on eBay.
https://zcardepot.com/products/big-throat-borla-throttle-body-60mm-280z-280zx
 
 

That’s what I have now, a 60mm TWM. The throttle has some issues with smoothness hence the desire to change it.

[wheee!]

I can transition the 70mm down too.

[Patcon]

I would think the larger TB would make partial throttle resolution worse not better. Unless it's some other aspect giving you issues

[wheee!]

I would think the larger TB would make partial throttle resolution worse not better. Unless it's some other aspect giving you issues

It’s more the unpredictable throttle blade movement and return. Sticky and screws up my tps sensor too. The billet throttle is very smooth plus incorporates a port for post throttle IAC control. A pre throttle port for egr too.

[wheee!]

This new throttle has a proportional throttle wheel too.

[Captain Obvious]

So if the problem with your original throttle body is mechanical stickiness from your cable linkage design, maybe we could work on fixing that instead of completely switching to a different throttle body?

But if you already have your mind set on a different TB... It's a long shot, but what is the possibility there is enough meat to add some additional new mounting holes? They can be smaller than the originals (which I believe are M8). If there's enough room to add some M6 holes in the flange without overlapping the original holes?

Something like this:

Or how about some custom studs that are M8 on one end to thread into the intake manifold, and M6 on the other end to pass through the (larger than they would need to be) holes in the throttle body? Maybe enough meat in the throttle body to use a file to slot the holes enough to get the smaller M6 bolts to clear? It's just a throttle body and it doesn't weigh a lot. Not a lot of load. And it would still seal against the gasket.

Yeah, it's a little hacky, but would be easier than welding the holes shut and starting over.

[wheee!]

I was also thinking of using an aluminum rod, threaded to fit the intake holes and sealed up then drilling and tapping new bolt holes in the intake to match the throttle body.
Or - make a space that has a plate to fit the intake with 60mm spaced holes then a tube tapered from 60mm to 70mm with another plate with 65mm spaced holes. This would serve both purposes of matching the bolt holes and adjusting the flow diameter.
The intake side is just bolt holes but the TB side would need to be threaded to hold the throttle body.
I wonder if a 3D printed piece would be strong enough??

[Captain Obvious]

I know it's a lot of reading, but take a look through this thread starting on about page 6 or so. There is also a bunch of talk about making adapters and such.

https://www.classiczcars.com/forums/topic/64413-just-another-damned-z-car-project-thread/?page=6

 

[wheee!]

I read most of that post but missed a few important points. Specifically the stock bolt spacing!

[Captain Obvious]

Haha! No big deal. I was just thinking there was a bunch of discussion about different adapters ideas bantered about. Might give you some ideas.

[wheee!]

I have a friend 3D printing a double flange adapter that tapers down from 70 - 60mm with two different bolt spacing templates. 1/4” thick flanges and 1/8” tube wall. Might use this as a template for a billet aluminum prototype. Unless we can find a suitable 3D material for strength and heat resistance.

[Zed Head]

I don't know why they've changed the name to "additive manufacturing" but if you use that search term you can find a lot.  Stereolithography > 3D printing > additive manufacturing > goofy.  Pick a name and stick with it!

Metals are possible.

https://www.additivemanufacturing.media/kc/what-is-additive-manufacturing/am-materials