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Fast and Powerful: Race Engines Aren't Just Race Engines
By Jim Walbolt
In the world of motorsports, high performance engines come in virtually unlimited configurations. From a one-cylinder lawn mower engine to a 12-cylinder aircraft engine and nearly anything you can imagine in between, people will race anything. Like the variety of engines, every sanctioning organization has its own rules and specifications for engine design.
Chances are, if your shop builds complete motors, or if you are looking to get into this market, you probably only specialize in a few types of engines. It would be nearly impossible to build hundreds of different types of performance engines – even the largest performance engine builders limit the types of engines they build. They know what they are good at and stick with it. It’s much better to become very good with one or two types of performance engines than try to be an expert at all types.
Shops that do machine work but don’t build the engines can get into a little more variety, but again, you would be much better off concentrating on those things you are best at. It is also important that you know the rules and specs of the performance engines you are doing the machine work for.
For instance, if you specialize in crank work and are preparing a crank for use in a Southern Automobile Racing Association (S.A.R.A) Series motor, you need to know that S.A.R.A. doesn’t allow knife edge cranks, and the stroke must be stock for the particular stock block used. An example would be a Chevrolet 350 that has a stock stroke of 3.48". This organization also specifies the blocks allowed by part number, so it’s important that you are familiar with their rule book.
In NASCAR Winston Cup Series and Busch Series, Grand National Division, along with ARCA racing, there is a maximum of 12:1 compression ratio allowed. ARCA allows a maximum displacement of 358 cubic inches and a minimum displacement of 339 cubic inches. You will find other organizations that have unlimited cubic inches. It is also important to note that NASCAR, along with a few other sanctioning bodies, has a number of "approved" parts and pieces that must be used. NHRA has a huge list of approved part numbers for many of its different classes.
The point is, when doing any high performance work, it’s important to be familiar with each sanctioning organization’s rules and specifications for each engine you are building for a particular sanctioning body. You may – and probably will – be asked by a customer to build something that is not legal for a particular organization. Racers are well known for their attempts to "stretch" the rules.
It is a personal decision whether you honor such requests or not. Keep in mind that if you do something "illegal," the sanctioning body in question could bar you and your engines or parts from competing in its future events.
You must also consider the aspect of cost. Even if you’re new to high performance work, you know that the costs are extremely high. Although most racing series have no limit on what a competitor spends on his engines, some series have what are called "claiming" rules. For instance, the IMCA has a $525 claiming rule for its modified division, and a $825 claiming rule for its sprint car division. If you finish in the top four in either division in a race, your engine can be claimed by any other driver in that race; in essence, purchased for the claim amount.
Competitors running with IMCA need to have the best engine they can get, at the least cost. It sure wouldn’t pay to build a $15,000 engine that can be claimed by another competitor for $525-$825. Of course, if the driver never finishes in the top four, it wouldn’t matter how much he spent. No, you can’t build a good race motor for under $1,000, but it sure is an incentive to build one as cheaply as possible. At least in IMCA’s case, this claiming rule has helped to even up the field somewhat as far as how much is spent on engines.
Another very important consideration when building high performance engines or parts, is the difference in seemingly similar engines and applications. For instance, although a tractor pulling motor and an alcohol drag motor are similar, they are also different.
The biggest difference is the fuel curve: whereas a drag motor requires a tremendous amount of fuel at the start and leans out at the end of a run, tractor pulling motors are the exact opposite, requiring little fuel (relatively speaking) at the start, and maximum at the end or near the end of a run.
In the Modified and Unlimited divisions of tractor pulling, the use of multiple engines is the rule. Number of engines used is determined many times by engine size and style, blower size, etc. Also, when running multiple engines, its best to have each engine be as equal as possible. Most of the time, a weak engine must be carried by the other engines, robbing them of horsepower.
The bottom line here is that you must know the application for each performance engine that you build or manufacture parts for. And, you also need to know the rules as to the engine specs for each sanctioning organization you build those motors or parts for in order to be sure what comes out of your shop is legal for that racing group.
With literally hundreds of different sanctions and types of racing in the United States alone, this can be a daunting task. Specializing in just a few types of engines is the smart move.