someone asks for a real hot rod engine that produces the maximum power for its displacement, then the price tag quickly escalates to Pro Stock levels.

        You can compare buying an engine to buying a piece of tubing. If I order a three-foot length of steel tubing with a certain diameter and wall thickness, the clerk at the metal supply can quote me an exact price. But if I want some exotic aerospace material, and I don't know the length, diameter or thickness, there's no way the guy behind the counter can give me a price. It's the same with racing engines: I know what it costs to build a 1,000-horsepower bracket racing big-block because I've done it dozens of times - but I have no idea what the price tag would be for a 1,400-horsepower Pro Stock big-block because no one has ever built one.

        I've noted in previous columns that rpm plays a major role in determining the cost and maintenance requirements of a racing engine. Any engine that regularly turns more than 7,500 rpm really needs lightweight valvetrain components - titanium valves, top-quality rocker arms, serious valve springs. On the other hand, if a 7,000 rpm motor will meet your power requirements, you can build a relatively inexpensive engine that will be virtually 

bulletproof.

        So how big is big enough? I'm sure some engine builders will disagree with me, but I believe the practical limit for a conventional Chevy big-block with 4.840-inch cylinder bore centerlines is 615 cubic inches. I want to emphasis the word "practical." Back when Buddy, Lee and I raced Mountain Motors, we built 655ci Rat motors with standard blocks, but those were extremely labor intensive. When you consider issues such as camshaft, connecting rod, and oil pan clearance, a 4 5/8-inch stroke crankshaft is about the realistic limit for a standard big-block.

        If you want to build a big-block with more than 615 cubic inches, my advice is to go all the way to an aftermarket block with a raised camshaft, spread oil pan rails, and 5.00-inch cylinder bore centerlines. There's no reason to beat your brains out to get 20 more cubic inches when it's just as easy (and just as expensive) to build an engine that's 100 cubic inches bigger. I wouldn't even consider a block with a 4.900-inch bore centerline like we use in Pro Stock; the little bit you gain with .060-inch more spacing between the cylinders simply isn't worth the expense for a bracket-type engine.