Stock Car Engine Comparison - Two Paths To Power

Even a casual fan of stock car racing knows that a NASCAR Nextel Cup engine is the cutting edge when it comes to standard V-8 engine design. In terms of over-the-road cars, the technology is a bit dated-pushrods, cast-iron block, flat tappet camshaft, and a carburetor are just a few of the limitations imposed by the rule book-but the Nextel Cup engine builders, who are among the very best in the world, still find ways to squeeze ever-increasing amounts of power from them. Currently, we are talking about well over 800 hp for a 358ci engine. Not bad for an engine design that was born over 50 years ago.

This raises an interesting question: Late Model Stock race cars run nearly identical pieces-pushrods, two valves per cylinder, flat tappet camshaft, and even the cubic inch displacement is identical-but they produce less than half the peak horsepower of their Nextel Cup brothers. So what accounts for the difference?

There are a couple of obvious answers to this question. The biggest contributor is probably the carburetor. Nextel Cup teams use a Holley 830-cfm four-barrel carburetor that has been "massaged" for maximum efficiency and will actually flow in the neighborhood of 900 cfm. Late Model Stock teams, however, are normally restricted by the rules to a 350-cfm two-barrel. The difference is the Late Model carburetor simply will not allow as much of the air and fuel charge into the engine to be turned into power.

Carburetor differences account for much of the dissimilarity, but that hardly tells the complete story. To take a closer look, we traveled to Lafferty Engine Creations in Concord, North Carolina. Owner Chris Lafferty worked for years building Nextel Cup and Busch Series engines in different engine shops before breaking off on his own to start LEC. Now he builds engines for a wide range of racing types. His bread and butter is building engines for Late Model and touring series, but he is also developing a Nextel Cup program for a team that is still in the formative stages. LEC is one of the few shops around that is currently building at both ends of the race-engine spectrum. Plus, we're grateful Lafferty was one of the few builders willing to take the covers off his Nextel Cup engine and allow us to poke around at anything we wanted to look at.

Interestingly, Lafferty says the biggest differences between the two engines are the cost and time involved. A new Nextel Cup engine will sell anywhere between $60,000 and $100,000, depending on the builder. The lower price reflects only parts, assembly, and preparation. When you factor in the extensive R&D necessary, the total cost involved can soar well beyond 100 grand. On the other hand, the going rate for a good Late Model Stock powerplant is usually between $16,000 and $20,000. (A good example is camshafts: Lafferty spends $1,000 on a Nextel Cup camshaft that will last one race, while he can get a Late Model cam for approximately $150 and run it an entire season.) An engine builder can easily build an LMS engine that's much more expensive than that, but the market simply won't support it. These cost considerations, not typically the rule books, are what create many of the discrepancies between Nextel Cup and Late Model engines. This also carries over to the time involved. For assembly alone, Lafferty will spend at least 30 hours building a Nextel Cup engine-most of that time is spent checking and rechecking tolerances. On an LMS engine, the time is between 15 to 20 hours, depending on the rules involved.

So, sit back as we take a comparison tour through a Nextel Cup and a Late Model Stock racing engine. The LMS engine is legal to NASCAR Weekly Racing Series rules, but it's typical of LMS rules run on asphalt tracks throughout the country. There are too many differences to hit them all, short of writing a book the size of Webster's Unabridged, so we picked out just a few of the more interesting, and more recent, changes. If you are a race fan, we think you'll find it interesting to see just how far the big guys will go in their chase for horsepower. If you are a Late Model racer or engine guy, we hope this story gives you some ideas for squeezing out just a few more ponies.