By David Reher, Reher-Morrison Racing Engines
It’s often said that the only difference between men and boys is the price of their toys. Forty years ago, I earmarked the profits from my newspaper route to buy a new bicycle; today I can hardly wait to pick up my new 2001 Pro Stock Grand Am. I tell my accountant (and my wife) that a new race car is really an investment, a tool to promote our business and to keep Reher-Morrison Racing Engines on the leading edge of engine development. But just between you and me, I wouldn’t be gearing up for 24 weekends on the road next year if I didn’t enjoy racing.
This is the time of year when racers are making plans and acquiring parts for next season. My advice to any sportsman racer who is considering a new engine is to think big. Cubic inches should be at the top of your shopping list.
Think about your long-term goals before committing yourself to an engine you’ll have to live with for a long time. Your immediate objective may be to run 9.90 or to qualify for the Quick 16 show at your local track. But after a while, you may find that running the number in Super Gas no longer feels like a fast ride – or you may discover that it takes a significantly quicker e.t. to make the cut for the fast brackets. If you buy a big-inch engine today that will satisfy your need for speed far into the future, racing will be a more successful and more satisfying pursuit.
When you are starting from scratch, the additional cost of engine parts for a large displacement engine is almost negligible. The prices of connecting rods, lifters, bearings, camshafts, oil pumps, and many other components are the same whether you are building a 396-cubic-inch big-block or a 632. Why not build a big motor and reap the benefits of more power?
A large-displacement engine makes a race car easier to run, simpler to maintain, and more consistent to drive. Cubic inches can compensate for a converter that’s not quite perfect or a car that’s a few pounds too heavy. If you are racing on a four-tenths Tree, the torque of a big motor will move the car harder on the initial hit of the throttle, breaking the beams quicker and cutting your reaction time. That all adds up to more round wins.
Big-inch engines can also be less expensive in the long run. Valvetrain maintenance is directly related to rpm; large displacement engines typically produce maximum power at lower speeds, thereby extending valve spring and lifter life. The extra torque of a big-inch motor lets you use a tighter, more efficient converter that won’t overheat the fluid, which enhances transmission life. Massive torque also eliminates the need for exotic and expensive gearsets; a big-inch big-block is a perfect match for a Powerglide with a strong and inexpensive 1.76:1 first-gear ratio.
There are two yardsticks to measure an engine’s output: horsepower per cubic inch and horsepower per dollar. In a heads-up class like Pro Stock Truck, power per cubic inch is everything. That’s why a 358ci small-block Pro Stock Truck motor that is capable of producing 900+ horsepower costs between $75,000 and $110,000. If you aren’t concerned about running on a class weight break, you can buy three or four big-inch big-blocks that produce 1200+ hp for the same amount of money. The price of power in a 358ci Pro Stock Truck engine is roughly $111 per horsepower; in one of our Super Series 565ci big-blocks, each horsepower costs less than $24. The bottom line: You get a lot more bang for your buck with a big motor!
I grew up building and racing small-blocks, but I recognize that times have changed. It’s a big-block Chevrolet world in the sportsman classes. I still have customers who are partial to small-blocks, but in good conscience I can’t encourage them to build even a 400ci small-block for any Super-type eliminator. We’ve built some really nice small-blocks for customers who insisted on running mouse motors – and six months later, many wished they’d bought a big-block instead.
In our shop we work on engines that range from early-model Hemis to Ferrari V-12s, but I wouldn’t recommend any one-off powerplant for serious sportsman racing. It’s all right to be different, but you should recognize that custom-built engines are not as cost-effective (and usually not as powerful) as the popular and affordable big-block Chevrolet combinations.
There are practical limits to engine size, of course. Building an 816-cubic-inch big-block, for example, is a very expensive undertaking that requires specialized parts such as a raised-cam aftermarket block, a billet crankshaft with center counterweights, a notched oil pan, and other custom-made parts. On the other hand, a standard 9.800-inch deck Chevy big-block with a 4.250-inch stroke crankshaft and 4.600-inch cylinders makes a very nice 565-cubic-inch package that will produce over 1,050 horsepower with a good set of ported conventional heads. A 10.200-inch tall-deck block with a 4.750-inch stroke and spread-port heads will get you 632 cubic inches and 1,250 horsepower at the flywheel. Those are straightforward, proven combinations that are tough to beat on the horsepower-per-dollar scale.
Yes, it is possible to build even bigger engines with a cast-iron factory block, but then you are looking at a more fragile camshaft with a reduced base circle diameter, increased piston-to-counterweight interference, and potential windage and oil control issues. Solving these problems turns the horsepower-per-dollar curve upside down. Since your objective should be to maximize the horsepower return on each dollar invested, I recommend staying within the practical displacement limits of the cylinder case.
The key to getting maximum value is to stay with a popular combination. At our shop we machine a dozen blocks at a time to identical dimensions and CNC port a pallet of cylinder heads before changing the setup. This reduces our labor costs, which in turn allows us to deliver more power for less money to our customers. Back when I was racing 287ci small-blocks in the early ’70s, I never imagined that one day we would have a mini-assembly line to build big-inch big-blocks.
Some racers resist the idea of using a block with the largest possible cylinder bores. I think this is a misconception that was born in the days when forged pistons were only available in .030-inch and .060-inch oversizes. I assure customers who are concerned about rebuilds that custom pistons are available in any size; when you’re racing a 632-inch big-block, you don’t use off-the-shelf “universal” pistons. If an engine needs its cylinders honed a couple of thousandths larger during an overhaul, it’s going to get .002-inch oversize pistons; there is no need to go all the way to .030-inch oversize pistons. If the bores are worn or if there is some shrapnel damage from a broken lifter, it usually only takes a few passes with a cylinder hone to clean up the cylinder walls. If something catastrophic does happen to the block, it is probably going to be unusable regardless of the size of its cylinders.
Today we build all of our 565ci and larger bracket engines with 4.600-inch diameter cylinders. The simple fact is that big bores produce “free” horsepower. There is no appreciable difference in the prices of 4.560 and 4.600-inch pistons, so why not get all the cubic inches that you can? An engine that produces nearly two horsepower per cubic inch will gain almost 20 horsepower at no additional cost by increasing its displacement by ten cubic inches – the difference between 4.560 and 4.600-inch diameter cylinder bores. The bigger bore diameter also unshrouds the valves and improves breathing, thereby adding even more power. With a siamesed-bore block, the difference in cylinder wall thickness between a 4.560 and 4.600-inch bore simply isn’t worth worrying about.
We’ve all heard the adage that there is no substitute for cubic inches. In truth, there is a substitute: cubic dollars. But unless your name is Bill Gates, my advice is to go for the inches and save your dollars for road food.