I Say Engine, You Say Motor

I Say Engine, You Say Motor

Over the winter I had had an engine rebuilt as a race engine. The old 1.8 liter M10 engine in my 318i, an engine almost identical to the engine in the 2002 (although with less displacement), had 203,000 miles on it, and dribbled oil from about 19 different places. Amazingly enough, it still ran like a charm, but I didn't want to be stranded far from home when it gave up the ghost in the middle of a race. It was a small miracle every time it survived another track day and made it home. It was extremely hard to fit $3000 for a professional race engine rebuild into my first year's budget, but I made it work, somehow.

Ken and Wes Hill pointed me in the direction of Mike Kolbert at Kirkland Auto. Mike is an outstanding machinist who does both machine and assembly work for a variety of vintage and ICSCC race cars, including several of the BMW race cars. I spoke with Mike, as well as a number of other local machinists and engine builders. All sounded very knowledgeable, so the decision was not an easy one. I considered having someone else machine on the head, with Mike doing machining on the block and final assembly. Another engine builder I spoke to had a lot of very "trick" things he wanted to do to the engine to eek the last possible bit of power from it. I also spoke with the folks at Metric Mechanic, and while I was very impressed with their knowledge and recommendations, they did not have the advantage of being local. Ultimately, I settled on Mike because I felt he really understood my primary goal: a reliable engine that was fully legal within the restrictions outlined by the Conference Production class rules.

Throughout these long conversations, I noticed that there was the usage of a lot of jargon: long blocks and short blocks, cams, heads, rods, pistons, cranks and so forth. I also noticed that almost everyone used to the term "motor" rather then the technically more accurate "engine". According to the dictionary, a "motor" is an electrically powered contraption, while "engines" are powered by gas. Motor. I tried to remember that. There was a lot I needed to learn.

I gave Mike the engine from Ken and Wes's 318i parts car. As a learning experience, I really wanted to assemble the engine myself, but it didn't strike me as a great idea to be doing this for a race engine -- I wanted something, first and foremost, that would be reliable. I will give this a try sometime In the future when I have more expertise and a better work surface then the kitchen table. I suspect this will the subject of an article titled, "The UnSage Mechanic Tries to Make Lots of Very Complicated Whirring Bits Fit Together and It Blows Up On His First Race".

Despite not being able to do the assembly myself, I found that throughout the process Mike Kolbert was happy to accommodate and patiently answered my stupid questions. After about the nine-hundredth or so, I suspect that even he was imaging ways of strangling me, but he never stopped patiently answering my questions. At this point, my understanding of the mechanics of an engine were limited to a dim picture of hot metal spinning at extremely high speeds.

The first step to rebuilding an engine is to disassemble and hot tank it. It's extremely cool watching a grimy, ugly engine, choked with almost two decades of carbon and road fudge become a shiny, pristine brand-new looking set of parts. I'm not quite sure what is "in" the hot tank but I'm sure it must be something highly toxic, like Dr. Pepper.

The next step was for Mike to look over the various engine components and decide what needed to be replaced and what didn't. Unfortunately, the engine I provided him wasn't in great shape. The crank case of the engine had a large crack in it, and the crank itself was badly worn. For a few hundred dollars I bought a replacement engine from one of the local BMW folks that turned out to be in much cleaner condition. Mike continued to measure and inspect various components and provided me with a list of what needed to be replaced.

This was a great opportunity for me to look at a disassembled (and clean) engine. Being able to see the component pieces, and how things fit together, gave me a far better understanding of just how a crankshaft moves, what a rod is, what a piston looks like, and how the head of the engine is put together. I also found www.howstuffworks.com to be an extremely valuable resource for describing the components and cycles of an internal combustion engine, complete with cutaway animations that even I can understand (though with a bit of head scratching).

Essentially, the major components of a BMW internal combustion engine start with a large, iron block that contains the crank (a big, heavy spinning thing). The crank sits in the block and spins on bearings, just above the bolted-on oil pan. Attached to the crank are the "rods". On the end of the rod is the piston, which goes up and down in the cylinders. Bolted on top of the block is the head -- a smaller, aluminum block that contains, in this case, four intake and four exhaust ports. Each exhaust port has an associated valve that is actuated by a cam shaft in its proper timing to let air and fuel into the engine and exhaust out. Connecting the crank and the cam is a chain (or on some engines, a belt) that makes sure the timing relationship between the crank and its attached pistons, and the valves, are correct. If that timing is modified more than a tiny bit -- such as if the chain breaks -- pistons run into valves, and suddenly the engine is full of broken and bent pieces of metal. That's very bad. Everything else attached to the engine serves the purpose of getting the proper mixture of air and fuel into the engine, igniting it with a heat source (spark plug) and then spitting out the waste product as exhaust.

The next step was to order replacement parts -- pistons, rods, nuts and bolts, valves, an oil pump, timing components (gears and the timing chain) and dozens of other things. None of these items were terribly expensive, but there were a great many of them. I decided to work on the principle that, since I was already spending a bundle, it would be a good idea to use new parts where ever possible. I ordered the parts from Eurasian Automotive, and while the parts were inexpensive, the service was absolutely terrible -- and ended up costing me several hundred dollars due to damaged pistons. Any "savings" I received was negated. I would not even consider using them again.

Within the limits described in the G-Production class rules that I was aiming for, Mike machined the internal engine components. This included re-boring and slightly widening the cylinders, and smoothing the intake and exhaust holes in the head to match the intake and exhaust manifold gaskets, aka "gasket porting the head". The benefit of this is that it allows more air to flow into the engine, and reduces the work the engine must do to push exhaust out of the engine. Because this engine would be used primarily as a race engine, Mike machined the components to make the engine slightly "loose". This means that the tolerances between the different components are slightly larger than they would be in a street car. With looser tolerances, the engine will run very poorly when cold, but will run with less friction once it has been warmed up.

As I discovered, machinists measure things in "thous". "Three thou" means three thousandths of an inch, i.e. .003". A stock engine might have an OEM gap of "7 thous' between the cylinder wall and the piston, contrasted to a race engine which might have a gap of 10 thousandths. Complicating this is that BMW parts are metric, requiring a bit of conversion when ordering parts. Roughly, .04, or "forty thous" is equal to one millimeter.

Once the machining was complete, Mike sent my engine components to have them precisely weighed and balanced. All moving components in the engine, from the flywheel to the pistons were weighed, and if necessary had small quantities of metal removed in order to create a better balanced engine. This will help it run more smoothly and, again, with less wear and friction.

One day in May, Mike called me and let me know that the engine was finished. It was beautiful -- the block had been painted shiny black, with brass plugs. Sitting on this was the pristine, silver head. But I knew that the real improvements were inside the engine.