1963 MG Midget - Nissan CG engine & 3D printed manifold

Fantastic! Cleverly worked out neat install!

madmog - kind words indeed, many thanks

I had the flange laser cut from a CAD file I produced. There are lots of companies in the UK who will do one off laser cutting, some even quote entirely online. It is worth shopping around as the price does vary and it is also worth speaking with them about material and thickness as this can also have a massive impact on cost.

To produce the CAD I scanned a gasket and took some measurements. It is also worth printing 1:1 to check before committing to metal (don't ask me how I know!)

There are a number of free CAD packages out there, you would only need a very basic one able to output the profile in a DXF format.

I hope that is helpful,

James

Cheers samulis - there are some nice cams out there but they don't come cheap. Maybe further down the road I will look into them along with a ported head.

Progress is on hold until my order from PME arrives and I can get the gearbox back together...

James

I love that you’re putting this together as a potential kit. What kind of money would one be looking at assuming you’re able to move enough units to make it worthwhile?

merryck - I am working on costs at the moment. I want it to be competitive with a the cost of having an A-Series rebuilt (properly) to standard specification.

moggyman - I hope that is the case, it's a big market. I have been able to confirm that with the same modifications made to the sump as I have done on for the Midget the CG will fit a Morris. Obviously manifolds will be different but I don't see it being a serious problem.

So after getting the engine running I hit a problem when bleeding the clutch. I had cocked up the build height and the slave cylinder had come apart. Because I had converted to a concentric slave this meant the engine had to come out. I had made the mistake of taking a best guess at the setup as I hadn't looked hard enough for information about how these slave cylinders work.

A bit of digging brought up this document which was pretty helpful: www.rwdmotorsport.com/downloads/hydraulic_release_bearing_kit_instructions.pdf

With the engine out of the car again I figured it would also help to strip down the cylinder. This would confirm how it actually works and allow me to confirm whether a pedal stop is required.



Mondeo clutch slave removed from the car



Bellows removed to expose the internals



The assembly is held together by a press fitted ring in the end of the tube. This was prised out



Main body with the feed and bleed ports



Piston and tube as removed



The tube seals to the body with a square section O ring and the piston slides along it, sealing on both the tube and body. This piston pushes the plastic carrier and thrust bearing with the entire assembly kept together with the big spring.

With it all in pieces I was able to measure the diameters and work out the maximum safe piston travel. This unit has a 32.5mm ID and 43mm OD with a safe travel of around 10mm. The sectional area is 623mm2. When compared to the 7/8" master cylinder's 388mm2 area there is a ratio of 0.62:1 so the maximum safe master cylinder travel is 16mm. Measuring the piston travel in the pedal box there was 21mm travel. I don't think the slave had a chance... I have adjusted the end stop in the pedal box rather than fit a pedal stop. The pedal sits marginally lower but isn't very noticeable and travel is reduced to a safe 16mm. The clutch appears to have bled fine so the ports must still be working in the M/C. If I do have trouble with this arrangement I will put a stop in and return the start point to the original position.

Sorry if that was dull, I figured it may help someone at some point in the future.

As shown in the image above there is not a lot of room between the back of the cylinder head and the heater, certainly nothing like the space needed to run the Nissan thermostat housing. There have been several iterations in this area during the build. Initially I planned on running an A-Series housing with an adaptor plate but didn't much like that. Space was too limited and I was concerned about getting a good sealing face.

Version 2 was a flange and welded pipe arrangement.





This used the MG heater tap and Micra thermostat in a billet housing utilising two Micra covers



This system would have worked but was bulky and I wasn't happy with the remote thermostat setup. It also relied on quite a long 8mm bypass. I was concerned that the flow would be restricted too much with the thermostat closed to the point that the engine could overheat before the thermostat would open. It was also not very cost effective for production.

Back to the drawing board then...





In the end I came up with a billet housing that carries a thermostat. The outlet bore is machined with twin O ring grooves for a push fit pipe.



3D printed prototype







And the real deal. I am really happy with how it has come out.

We’ve just used an FX4 heater valve to enable the bypass loop or heater on the Land Rover as this was needed to keep the later engine in an earlier car happy. (2.3 petrol 110 engine into aseries 3).
Nice project.
James

I'm no good at technical help, but I van add that I think this is a fantastic conversion. I too think it keeps the spirit of the Midget but updates it!

I'm trying to convince a good mate of mine to go down this route with his Mini

Tom

Cheers! I got the idea while helping (watching) the much better half wrapping the drop bars on a Coventry Eagle she has restored. A proper period-looking engine bay is just the stuff of, well... but there was no way I was paying Samco Classic prices. Hopefully it will hold up.

James