Since I have a spare manifold and throttle bodies which I'm cleaned up and refurbishing, I've decided to get the stock throttle body intake ports enlarged with larger butterflies similar to the modification that Rob Bastian (RobZ) was doing for people a while back.

 

I'm not sure if anyone is familiar with this modification, I believe 54mm is the largest you can go to in stock throttle bodies (originally 50mm).

 

Can anyone confirm whether this is the max or can they go any larger?

Edited December 2, 20187 yr by Funkysi

I believe Z1 took theirs up to 58mm?

I would like to learn more about this mod and how to do it. Please share Si.

 

Ta

 

Sayers

Are you getting the 2.5” pipe work Simon?

Are you getting the 2.5” pipe work Simon?

 

That's not answering my question. :lol:

 

The intake is much smaller than even the stock pipework, so it will make an increase. If you put 2.5" piping on, you're still reducing when you go into the throttle chamber.

But yes, eventually. :)

well after doing some CAD work, when taking the throttle bore out to 54mm which leave 0.35mm material left from bore to casting, boring it out to 56mm which possible using the oem seals, shafts, ect would need some extensive work and money to have a 56mm throttle body as it eats into the space of the bearing seat. I'm going to have a go at a 56mm throttle body as I've done the CAD work and when finished it should look like OEM from the out side and a 56mm throttle plate on the inside......!

 

when have worked out if can post photo's I'll put some up.

well after doing some CAD work, when taking the throttle bore out to 54mm which leave 0.35mm material left from bore to casting, boring it out to 56mm which possible using the oem seals, shafts, ect would need some extensive work and money to have a 56mm throttle body as it eats into the space of the bearing seat. I'm going to have a go at a 56mm throttle body as I've done the CAD work and when finished it should look like OEM from the out side and a 56mm throttle plate on the inside......!

 

when have worked out if can post photo's I'll put some up.

 

This information may help you re going over 54mm with stock throttles:

 

http://www.twinturbo.net/nissan/300zx/forums/general/view/2471347/The-problem-with-the-barrel-method-is.html

 

The work by Robert (Rob'Z) in the states on modifying stock TB's is here:

 

http://www.twinturbo.net/nissan/300zx/forums/general/view/2471246/Fun-with-the-CNC-lathe.html

 

This a picture of the throttle shaft milled down:

 

Edited February 4, 20196 yr by AndrewG

I've also found this which would help if your just cleaning the throttle bodies ect.

 

https://www.z1motorsports.com/imageGallery/main.php/v/Shop-Pictures/album291/album297/

 

https://www.z1motorsports.com/imageGallery/main.php/v/Shop-Pictures/album291/album292/

I've also found this which would help if your just cleaning the throttle bodies ect.

 

https://www.z1motorsports.com/imageGallery/main.php/v/Shop-Pictures/album291/album297/

 

https://www.z1motorsports.com/imageGallery/main.php/v/Shop-Pictures/album291/album292/

 

Those pictures are of Z1's 58mm TB's using another OEM TB's (I'm not sure what car they came from). They stopped selling them as customers

were experiencing problems down to poor machining.

 

http://www.twinturbo.net/nissan/300zx/forums/general/view/2436993/Anyone-else-have-issues-with-their-Z1-58mm-throttle-bodies.html

 

They went onto producing their own CNC'd 58mm TB's and after two versions stopped selling them. The V1's had all sorts of problems again

with machining and QC. I'm not sure why the V2's were discontinued.

 

http://www.twinturbo.net/nissan/300zx/forums/general/view/2488772/Z1-Motorsports-58mm-CNC-Throttle-Bodies-V2-now-available.html

The back of the throttle bodies are flat with out any casting indents which I think these are there own castings.

 

 

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Well after a few weekend of make the parts I need to machine the throttle bodies, both are bored out to 56mm and now machining the throttle plate to mach each bore. Before boring the throttle bodies I checked the roundness and you could pass it as an egg shape....! So when cleaning your throttle bodies do not remove the black paint on the throttle plate or bore, I have all so made some new spring spacers. The Z1 58mm throttle body came from a 200sx with the part from 300zx excepted the throttle plate.

 

 

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You've taken Z32 TB's out to 56mm? Have you reseated the bearings?

Yes, OEM z32 throttle body to 56mm and moved the bearing out by 3mm each side.

 

 

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Looking forward to the photos of your work Iain - well done!

Here you go

I have put the OEM throttle plate on top of the 56mm to show size

Last two with out new 56mm throttle plate .....!

 

 

 

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can you make this upgrade at any time?

Well after refitting the springs on both sides ( thank goodness I found the Z1 motorsports instructions as for fitting the springs) I'm pleased how they have turned out. I replaced the 26x8mm bearing with 19x5mm, both have 10mm bore

I can say that looking into the Z1 throttle bodies are new casting which are then machined with bearing seats moved out.

 

 

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I replaced the 26x8mm bearing with 19x5mm, both have 10mm bore

 

I did wonder how you had managed to accomodate the shaft seals within the reduced space available.