Cars


Mini Rebuild

 

Step 71 - A Change of Plans

 

A young critic detailed a previous position Bertand Russell had taken and noted an inconsistency with his current position.
Russell declared, "Young man, I changed my mind."

 

Last summer I drove the Mini from our old place to our new one. It didn't go well. Nothing awful happened, other than repeatedly stalling it, but the experience was not what I was looking for. Way, way more noise than I wanted to hear - from boththe intake and exhaust. The engine RPM's were far higher on the highway than I anticipated. I knew that installing a motorcycle engine into a car would entail some compromises but this was a bit much. So after all these years of hard work, I was suddenly unsure of the direction I was headed and there was still plenty of development time left until the car was fully sorted. Time for some reflection...

 

Sadly, "reflection" turned into "ignoring the car that was now rotting in the garage". Almost a year of "ignoring" had passed when my father gave me some great advice: "Sell the car as-is, finish it with the R1 engine, or take it in a different direction, but it does you no good as it is. Whatever you decide to do with the project, do it. You can't do nothing." He was right.

 

After much thought, I decided that the R1 engine had to go. I wanted many of the modern enhancements that came with the motorcycle engine (high specific output, the ease of tuning that F.I. provides, etc.), but would prefer to do without some of the compromises (stalling off the line, excessive revs on the freeway, no reverse gear, etc.). To be clear, I am not putting the MinieXvo kit down. It is a fantastically engineered thing and I have been contacted by a few owners around the world that are enjoying them (usually on a racetrack. hmmmm...). The problem is simply a misalignment that grew between the kit's purpose and my intended use of the car.

 

So putting an original Mini A-series engine and transmission into the car seemed the logical choice but it still wasn't exactly what I wanted. Driving almost anywhere in California involves freeways and that means driving 70+. The standard A-series' 50-70hp makes that a noisy, high-revving, and overheat-inducing proposition. More power is possible but to get it means some sort of compromise in the powerband. So now I'm back to a peaky, high-revving engine that is a chore to get off the line.

 

Mini Rebuild Step 71

 

Mini Rebuild Step 71

The A-series in stock form. You'll notice the carb and exhaust manifold together on the back side of the head with nothing but sparkplugs in front.

 

The issue is the head. A lot of development has gone into improving the A-series head design. It is probably the single biggest thing holding back the engine from making more power, although it should not be forgotten that this engine was designed in the 1940's and nothing beyond reliable transport was envisioned. It is a 2-valve per cylinder design with a reverse flow and siamesed ports. Simple but effective. For more power, ideally the head would be crossflow, with 4-valves per cylinder. And although some people have gone to great lengths to manufacture small batchs of crossflow heads for the Mini, it turns out BMW already made a great head for the A-series back in the '80s!

Mini Rebuild Step 71

 

This gentleman found that the head of BMW Motorcycle's K100 engine would fit onto the A-series block with only some basic modifications required. The cylinder number and spacing lined up perfectly. That's quite a coincidence, but it gives us a relatively modern 16-valve, twin cam, crossflow head with individual throttle bodies and fuel injection! Even better, there are several companies creating do-it-yourself kits as well as turn-key builds. Earlier this year I settled on the latter, available thru Specialist Components.

 

Mini Rebuild Step 71

The BMW K100 sport-touring bike of the late 80's/early 90's.

 

Mini Rebuild Step 71

 

Mini Rebuild Step 71

It took a few months to get built but eventually it found it's way to my front door.

Mini Rebuild Step 71

 

Mini Rebuild Step 71

Individual throttle bodies, fuel injection, and modern coilpack ignition.

Mini Rebuild Step 71

I would very much like to finish this entire project and get the Mini on the road. Therefore, I immediately set to work. I rigged up a mount to hold the assembled engine so I could install the exhaust headers and start installing the plumbing. The black hoses on the left side are for oil and coolant. The blue lines are for engine breating and will all terminate at an oil breather/accumulator.

 

Mini Rebuild Step 71

 

Mini Rebuild Step 71

 

Mini Rebuild Step 71

I added some heat insulation to the breather lines where they pass near the headers.

 

After the plumbing is complete, I will drop the engine into the engine bay to check a number of items. Since I modified any number of things to make my car compatible with the MinieXvo kit, I will have to undo some of those changes to work with this engine. More on that soon.

 

Continue to Rebuild Step 72

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