Blog 06 - CA to VG transmission machining

December 21, 2025

Preface:

A few months back a fellow from Alberta contacted me, asking if I could machine his VG bellhousing for a maz-worx adapter plate. I was sceptical at first, but I measured my milling machine and it seemed like it could work.

The costs involved with sending it to the US for machining are fairly high with tariffs and international shipping at the moment, and it sounded like no local shops in his area wanted to do it, so he decided to ship it to me in BC to do the work.

As a fellow CA owner, I was keen to give it a go! I also have a 300zx transmission I want to eventually adapt to my CA, so it would be a good opportunity to see how everything works as well.

The process:

First task was to tram the head. I had never even done this since I bought the mill a few years ago. My mill has a column riser put in that someone made, so I popped 0.003" of shim stock under the back where the head meets the riser, and that got it trammed in.

I made sure all the gibs were a little tighter than normal. Since I'd be using so much of the mill's Y-axis travel, I wanted to make sure the table wouldn't lift when the travel was close to max'd out.

Now I could mount the bellhousing on the machine:

After making sure the table and bottom face of the bellhousing were clean and burr free, I used a couple step clamps + a long threaded rod through the middle of the trans. This was lots of clamping force to hold it down.

Due to the small size of mill/shape of the bellhousing, I had to machine the depth for the plate in 2 setups. First half went well:

Then I spun it 180 degrees and did the 2nd half:

On this project, I was paranoid about nailing the dimensions; I ended up feeding the depth with the Z-axis/knee, as I heard this was most accurate compared to using the quill (and that has been my past experience too).

When I took the final pass on the 2nd half of the bellhousing, the surface finish blended perfectly into the other half of the machining. This confirmed everything worked out well, despite doing this in 2 setups.

Next up was a couple locating bores for dowels on the adapter plate. Luckily, mazworx supplied me with a drawing for this (big thank you!).

I needed to align the Y-axis parallel to the 2 main bolt holes at the top of the bell-housing, so I made these pins on the lathe to help me out:

Tapped them both in place (slight press fit), then I could reference off them with the dial indicator.

And the other one:

Perfect. That aligned the bellhousing as per the drawing. Next, I needed to use an existing hole as my origin - back to the lathe to make an alignment pin

I moved the Y/X axis until it slipped into this hole, then zeroed my dials.

First bore was to be located on the same origin hole. I plunged a roughing end mill down first, then switched to the boring head to dial in the final size:

Next it was over to the opposite side of the bellhousing for another bore.

And I just plunged the correct size end mill down to do this one:

With that done, it was time to make sure the adapter plate fit! Moment of truth...

Nice...

Ok, lastly. The starter clearance - The drawing included locations/dimensions for this too. So I started off with an undersize hole-saw to give me a boundary for milling.

I took this around 30 thou shy of full depth.

With a boundary laid out, I switched to a big end mill to hog out most of the material. I went to full depth here.

And finally, I used a boring head to finish off the OD nicely.

That was all the machining done, so I could remove it from the table for de-burring and cleanup. All in all, I'm quite happy this was able to be done on my half size bridgeport!

Here is a few shots of the finished product: