Building an engine for the street or the track: what’s the difference?

by: Justin Rhoads

I have been doing some reading lately and keep running into this notion that a “street” engine is built completely different than a competition engine. As an engine guy, I did a double take; that’s not the way I see it and if you think about it, it just doesn’t seem natural that there would be a difference.

Let’s start with the basic concept; how does one approach designing an engine package for a particular application? In the post “engine design, art or science” I outlined the process that I go through whenever I look at designing a particular package. I’ll reiterate a few of the main points here; 1^st determine the operational environment, 2^nd make concessions to optimize the engine characteristics for that environment with input from the driver and chassis guys, 3^rd test and refine the package to exploit the advantages produced by the driver/chassis.

So at the end of this process you have the best possible package for what the driver needs, the chassis can use, and the track favors; why can’t we substitute street for the track in this equation? The myth of these styles of engines being completely different and incompatible with one another stems from people not going through the above steps when developing their combination. I hear the term “planning my build” a lot and frankly, it sends a chill down my spine. You do not plan (ie pick parts from a catalog and go to town) until you have gone through the developmental process (the process is the PLAN).

There lies the problem; if you simply stick a well built, high budget drag race engine in a street car the results will be less than stellar (unless this is what the driver and the chassis favor). Not because the engine builder is crap, not because the parts are junk, but because the entire package is not optimal for the application. If the above methodology is utilized anyone can successfully build an engine that meets their needs.

Now I’m sure enthusiasts and engine builders alike are burning up their keyboards with emails stating “what about my clearances”. Your bearing clearances will reflect the viscosity of the oil used by the package, which will be determined by both the stresses imposed by the nature of the application and the oiling systems ability to cope with the required oil. A top level engine builder will not simply state “for a street car I set them up at X”; there will be a method to the madness so to speak.

In the end, the same process of development should go into any engine being built along with the attention to detail; the methodology is the same with only the parts selected being different. The same quality of craftsmen ship of the parts, the same attention to detail during machining and assembly that makes a top level competition engine shine, will lead to a long and happy life on the street.