This article first appeared in the April, 2016 edition of SportsCar Magazine. SCCA members can read the current and past editions of SportCar digitally here after logging into their account; To become an SCCA member and get SportsCar mailed to your home address monthly in addition to the digital editions, click here.

Part 1: The foundation of a good race engine begins with the short block

No matter what you drive, if you run it hard enough, for long enough, you’ll be servicing the engine. Having a top-flight engine in your racecar can be essential to winning – and an aging or poorly performing engine is often the difference between winning and losing. But, while building a performance engine isn’t always cheap, doing it right the first time can save you cash – and, more importantly, put you in a position to win.

Step one is selecting the engine block. It’s ideal if you can start with a known good block. Using your existing engine, even if it’s tired, is usually a safe bet. If you’re looking to build from a donor core, try to confirm its history.

Once you’ve sourced a solid engine block, the dirty work begins. “You’ve got to get the thing apart,” says John Edwards of Costa Mesa R&D Automotive Machine Shop. “Then we do a visual inspection. Look for cracks and corrosion damage. Once we deem it a likely candidate for a rebuild, then we clean the block. If it’s an aluminum block, it’s going to have to get a Zyglow test; for cast iron we would use a cast iron particle inspection to inspect for cracks.”

If the block passes the inspections, machining can commence. “From there, we move on to any machine work we have to do,” says Edwards. “Generally, the first thing we do is to check the main bearing housing bores. On a performance engine, we align hone or align bore the engine. We resurface the deck. We measure the surface finish when we are done, because some gaskets like a certain arithmetic average finish, so we want to make sure we achieve that.

“Next,” he continues, “we bore and hone the block. Most performance blocks are going to require the use of a torque plate – which simulates the cylinder head being in place – to ensure that when honing, the cylinder bores are not out of round. Once the machine work is done we clean it again, and then ad some type of lubricant to help prevent rust.”

Most SCCA classes have a certain overbore maximum, meaning there’s a limit to a block’s lifespan. “Once you go much over 0.040 [inches], you either have to find another block – and do all the normal steps to check it – or you have to put a sleeve in it,” Edwards explains. “Typically, if you have more than about 0.004 to 0.005 out of round in a cylinder, or it has 0.004 to 0.005 [inches] of taper, then it’s going to have to be bored to the next size. If you are already at the max overbore and it needs to be cleaned up again, you would go ahead and put a sleeve in.”

Once the block is ready, you can turn your focus to the rotating assembly inside the block. “The rods can be inspected and serviced or replaced as needed,” says Edwards. “The crankshaft will have to get checked, and will get micro polished or reground.”
Alan Rebescher, of Summit Racing Equipment, adds that if there is any doubt about the condition of your existing crank, it’s a good idea to replace it. “When a crankshaft fails, it’s usually catastrophic, so if you’re inspecting your motor and find the crank to be out of spec, replace it. When in doubt, throw it out.”

If you find yourself in the market for a new crankshaft, your choices are likely going to be dictated by the rules for your class, and your budget. It may be as simple as finding a suitable used core that can be inspected and reconditioned, or you might be looking for something sportier. “Let’s keep something in mind here,” says Rebescher, “stock cranks are designed for street driving, not racing. Even if your car is a factory high-performance model, it was not intended to be raced hard. Buy the best forged-steel crankshaft your budget will allow. Having the rotating assembly properly balanced and using the best harmonic dampener for that application will go a long way toward making your motor survive what you are going to do to it.”

The next link in the chain is the connecting rods. Some classes allow the rods to be modified or replaced and, in those cases, you have a number of choices. If you race a popular car, you will likely have your choice of a number of different rods to meet your needs, depending on power level, RPM, and use. You can also have rods made to suit your specific needs.

Bryce Mulvey, of CP-Carrillo, says they have hundreds of off-the-shelf applications, but can also do custom rods for unique or unusual applications. The customer starts by filling out a detailed tech sheet, and in about seven weeks, a set of custom connecting rods can be created from a raw forging. But going custom can be costly. “People wonder why rods cost so much – there is a lot of material waste, and a lot of machine time,” says Mulvey. “A piston we can produce really fast because it’s aluminum and it takes less time to machine; there are more steps in the process of making a rod and the machining takes longer.”

Unlike a piston or camshaft, the connecting rod does not offer the promise of increased power, but selecting a quality rod can help ensure the parts inside your engine stay inside.
When it comes to pistons, the choices are limited only by your imagination and wallet. From OE overbore pistons to complete custom units, these bits of aluminum can really help unlock some engines. And even with countless production piston options, CP-Carrillo notes that about half of its piston business is custom, made-to-order units.

If custom pistons are in your future, you’re going to need to supply a lot of information. CP-Carrillo has a detailed order sheet that covers every aspect of the piston. To simplify the process, CP-Carillo created a mold-making kit that allows you to take an impression of your cylinder head combustion chamber at home, negating the need to send your head in for measurements.

Once your spec sheet has been completed, the CP-Carrillo goes to work designing your pistons. It may be built from an existing forging, or in some cases cut from a billet. “We do a billet because it’s a weird combination of parts, or we don’t have a forging that will work,” says Mulvey. “A billet works for the weird stuff people dream up, or for testing, and then we make a forging based on that.”
Developing a custom piston can be a very intensive process. “There are a lot of different options and so many variables, it can take 10 hours for an intricate custom design, and something simpler may take an hour,” says Mulvey.

If you have custom pistons made, make sure you acquire the proper ancillaries with it. In the case of CP-Carrillo, they include the appropriate rings and wrist pins to complement the new pistons. Additionally, upgrading the hardware can help minimize failures. Quality studs and bolts are a good choice over OE units, particularly since many OE applications are one-use items.

When it comes time to assemble the bottom end, two things are of crucial importance: balancing and cleanliness. “We have to balance the cranks, rods, and pistons,” says Edwards. “We have to balance the crank with the flywheel, but we also like to have the damper and the clutch cover.”

Many engine builders will have a clean room that’s used specifically for assembly. Dust, hair, or any bits not completely cleaned up after the machining process can impact the lifespan and performance of your new engine.

Using an assembly lube is a must; it will protect vital components during startup. “Red Line’s Assembly Lube is a standard in the industry, based on the same molybdenum formula components in our motor oils,” says Cameron Evans
of Red Line Synthetic Oil. “This means the assembly lube hangs around until the oil shows up, in layman’s terms, then the lube emulsifies into the motor oil as designed.”

When you decide you’re ready to build the engine, plan well ahead, and give yourself cushion in your schedule, because the process will undoubtedly take longer than expected. There’s a lot of engineering, machining, and parts involved, and many vendors will have to communicate back and forth before the next step can be taken. And, with the bottom end built, it’s not over – there’s the motor’s head to think about, which we’ll cover in part two of the series.

Service It

A race engine is an investment with a lot of costly parts involved. To ensure top-level performance and longevity, you must take care of it. Beyond your regular maintenance regiment, you will eventually have to freshen it up, because unlike the engine in your road going car, a race unit is not made with longevity in mind. So, how often should it be freshened up?

“A lot of it is determined by how the customer takes care of the engine,” says Jesse Prather of Jesse Prather Motorsports. “ I’ve got guys who can go three years on engines, and I’ve got guys who can only go a season. It depends on whether or not they’re taking care of their oil, meaning not only are they changing it, but also maintaining proper oil temperature, water temperature, and revs of the engine.”

A variety of variables make a big difference in how long an engine can go, Prather explains. “The other thing that makes a difference is the ring pack. On a lot of these race engines, we run a smaller ring pack, and the smaller the ring pack you run the less time you’re going to get before the rings weaken and you get more leak down. The full prep guys are not getting a season out of their motors before they have to rebuild them, but that’s because of the high compression and high valve lift – everything wears a lot quicker. With a limited prep engine, everything is a lot less stressed. Generally, I tell my guys they can go two seasons and then refresh, with a season being five or six weekends, which is 12 races plus the Runoffs. Of course, the higher stress engines will only get about half that.”

Words by: Jason Isley
Image by: PDLDesign