The precision work of engine building is an endeavor that leaves little room for error. People make mistakes, but when mistakes happen in the engine-building process, redemption doesn't usually come as easily as hoping no one will notice, or asking for forgiveness. An engine is pretty intolerant of mechanical errors, and it will let you know, sometimes by not making the power you think it should, and sometimes with the poignancy of a calamitous, catastrophic failure. If you are lucky, you might be able to fix it, or start over and build it again. Other times the entire effort is reduced to a pile of scrap.

There really is no way to completely eliminate the potential for human error when building an engine, but there are steps that can be taken to minimize the possibility. First, become as familiar as possible with the engine being built. This usually comes with experience, but even a first-timer can gain familiarity by studying service manuals, books, and articles on the subject. The next consideration is preparation. This includes having the required tools-a clean, well-organized work space, and clean and properly sized parts. The final aspects are the actual processes, techniques, procedures, and checks made in assembling the engine.

Engine-building mistakes come in two major categories: assembly errors and component selection errors. We asked some of our top AMSOIL Engine Masters Challenge engine builders to point out some common engine-building pitfalls. These experienced professional engine builders have undoubtedly seen it all, and pass along their experience to help you avoid costly errors.

1 Too Little Rod Bearing Clearance
Tony Bischoff, BES Racing Engine
"An obvious one here is not checking the bearing clearance. It is a very common thing. A builder might think that a crank checks at standard specs-if it is checked at all-and figures the clearance is good. The worst thing to do on a race engine is have the bearings too tight, especially on a higher rpm engine, especially on the rods. When you spin them up the rod gets a little bit stretched and the big end pinches the bearing or it doesn't get enough oil to keep it cool enough, and the bearings fail."

2. Hone It Too Smoot
Tony Bischoff, BES Racing Engines
"Finishing cylinder walls too smooth is a problem I've learned the hard way that you don't do. The crosshatch is designed to hold oil to keep lubrication for the piston skirts and rings. You make the wall too smooth and the rings don't last as long and you can scuff piston skirts. I still see a lot of engine builders make this mistake to this day."

3. Too Big On The Cam
Tony Bischoff, BES Racing Engines
"The most common engine parts selection mistake is going too big on the cam. I see this a lot, but it's been a long time since I've done that since I learned a long time ago that you're better off going smaller than bigger. It's easy to go too long in duration, especially on a street car."

"It's easy to go too long in duration, especially on a street car."-Tony Bischoff

4. Too Much Compression
Tony Bischoff, BES Racing Engines
"Another common problem I see is people run too much compression. For example I might get a customer coming in with an engine asking for 10.5:1 and they are going to put 15 pounds of boost on it with pump gas. I'll tell them they need to turn it down a little bit, and they'll argue that it already runs like that, but they are bringing me an engine that is already burnt up from too much compression. The cylinder pressure has to match the octane and fuel you have."