Editing XF Throttle body (section)

===Tapering the plenum===

Now you need to match the plenum to the TB.
The BEST way to do this would be to weld up the valley around the TB flange on the plenum so you can have a straight hole going into the plenum.
If you don't want to do that, you will need to taper the TB hole in the plenum to try and match the XF TB.
This is what I did.

Ok, now with your XF TB bolted on, open the butterfly and using a fine point marking pen of some type, draw a circle of the area that needs to be tapered to.

[[Image:XFTB5.jpg]]

Take off the XF TB, and you will see what needs to be done.

[[Image:XFTB6.jpg]]

Get out the good old dermal and start having fun.
Make sure you make the line disappear to make a perfect match to the TB.
Remember, a little bit to big is less restrictive then a little bit to small.
I used tungsten carbonate bit to take majority of the metal off, then used a stone bit to even it out, then used sandpaper wheel to make it smooth.

I found it was easier to just taper it in on a fairly sharp angle first, then from there, work your way around grinding bits off to make the hole bigger, and constantly checking you don't take to much and go completely through the edge.

When finished, make sure to clean the plenum out perfectly because you don‚Äôt want heaps of those little metal bits going into your motor.
I used a can of spray degreaser (works better then normal stuff you have to splash around yourself) and cleaned out the inside of the plenum with that, and then good hose out with water.

Your plenum should like something like this now (not cleaned yet in the photo)

[[Image:XFTB7.jpg]]

Now you will need a gasket.
Take the standard [[RB30E]] gasket, and put on how it would normally go on. (put it in so its bolted between the XF TB and the plenum).
Now do what you had to do to mark the area on the plenum to be cut, but marking on the gasket this time.
Take off the TB and cut off part you don't need from the gasket.
You can now assemble the TB back onto the plenum with the gasket in it.
Do the TB bolts up tight while it's all off the motor because it's a lot easier to do now.