Mini Racecar Custom Valve Cover

The plastic valve cover has been problematic & prone to melting due to heat from the Turbo.  I painted it with a ceramic-based high temp paint to help protect it (a bit) from the heat.  It helped a bit. I also built & mounted a prototype "air scoop" to try to force more air down between the turbo & valve cover:

So moving the coils definitely fixed the issue of melting of wires. And it helped reduce the melting on the valve cover considerably. But there's still a small amount of melting regardless. I'm sure I could run a couple of weekends before it gets too bad, but the risk vs. reward is considerable.

So I decided to solve the problem the right way, i.e. an Aluminum valve cover. Since there are no Aluminum valve covers for Minis (that I can find), I had to design one myself. Because the shape varies in all dimensions, I determined it's best to have it machined out of a solid block vs. welded (casting is discussed below). Below are some pictures of my design.

The trickiest part of the design was the baffles for the PCV. I could have leaved the space & try to fabricate my own baffle system, but that would be complicated & potentially dangerous (if something came loose & fell down). Instead, I lowered the top of the cover to leave room for an external PCV system attached through a hole. This considerably simplifies the overall design & gives me even more airflow back to the turbo.

One slight problem: the software I used was somewhat limited. Finishing the remaining portions of the design (e.g. rounding the remaining edges, cutting the groove for the seal, cleaning up some of the corners & faces) was somewhat tedious & error-prone. I'm currently learning Solidworks for future projects.


The x-ray render mode is very useful for seeing flaws in the walls and intersections:

I considered doing a casting from a pattern, but decided against it for various reasons:

1. I knew the design would have to be modified no matter what, so I couldn't use the original as an exact model.

2. Given the shape, producing a good physical pattern would take a very large amount of effort.

3. Also given the shape I was slightly worried (perhaps incorrectly) about the potential of leaks from imperfections in the moulded part & mating surfaces.

One alternative I thought of for producing the pattern was to use software to stich photos of the cover into a 3d model & then print the the prototype from that. But that ended up being even more work due to cleanup needed in the model & moulds.

In the end this was really the quickest & easiest approach. I'll probably spend a total of 10 hours on the model - most of that because I'm learning the software at the same time. I can then give it to a shop with a CNC machine & they can quickly produce a clean, precise part. Moreover it's easily repeatable if I need another one in the future.

A huge thanks to Voigt Machine Inc. here in Houston for their extensive help in taking my vague ideas and getting them to work.

I simplified the design of the stock cover significantly - removing the built-in baffles and numerous extraneous curves & elements. I stuck with having a groove around the lip so that it uses the stock seal. And I found an off-the-shelf external valve cover vent with a built-in filter. It's a bit bulky but it works as a first cut.

Voigt was able to make it work on the first try. Here is what it looks like:


To seal around the spark plug tubes, I found an Aluminum baffle with inner and outer seals:


By cutting off the top it forms a perfect seal. You can see one installed in the images.

I have an old head I've used as a test block. First I did a test install on the car to check all clearances. Here's what it looks like:


The good news is that it all looks good. The only adjustments I needed to make are to trim off a bit of the bracket I made for the ignition coils. And I need to trim the rubber around the spark plug boots to fit better into the (slightly smaller and deeper) hole. I should be able to finish this up next week & start it up.

Now that I have a prototype, it's relatively easy to have more machined. Alternately, this could be used as a master for a cast version...

Thanks again to Jim & Craig at Voigt. They are miracle workers!!

Posted on January 5, 2014 .