Entry-Level Racing - Economical Race Engines

If your donor engine hasn't been damaged from overheating or detonation, it's likely that both the crank and connecting rods are reusable along with the block and heads. Still, it's a good idea to clip the caps and resize them (shown here). This process ensures that the rods are nice and round. Otherwise, it will squeeze the rod bearing against the crank journal. This can cause the bearing to shed layers, putting metal into the system, and eventually spin a bearing.

OEM rods aren't normally balanced as well as you would like for a racing engine. Plus, clipping and resizing the rods can throw them further out of balance. It's an easy and relatively cheap fix to weigh and balance your rods.

Stock rods usually have a pad of metal on both ends, which is there expressly to make balancing easier. Here, Kevin Troutman of KT Engines grinds some of the metal off one of the pads to bring a rod into balance. If the rods, pistons, and crank are all in balance, it reduces vibrations and makes the engine more efficient at turning the chemical energy from the fuel into kinetic mechanical energy.

If you want to reuse your crank, it's always a good idea to have it magnafluxed to check for cracks. Even if nothing is done to the crank, the piece must be thoroughly cleaned before reassembly. This includes the oiling holes, which can be done with a small, circular brush. Cleaning doesn't have to be done in a solvent tank such as this. You can do it in your driveway with a water hose and a bucket of soapy water. Just make sure to apply a coat of rust inhibitor such as WD40 after you are done.

Day Motorsports provided us with a rebuild kit, including a timing set and all the gaskets and bearings we needed.

It is tempting to reuse your stock pistons, but it's not always the best idea. For our engine, we decided to upgrade a bit. Even though we won't be upgrading the original horsepower significantly, OEM cast pistons are a liability because they simply are not designed for 30 laps around a half-mile track at wide-open throttle. Probe Industries had the Street Stock racer in mind with these pistons. They are high-quality forged pieces that can easily pass for stock. They are targeted for claimer engines-affordable so you can stand to lose them, but good enough so that you can win with them.

Our main bearings are installed in the block. Troutman says if he could perform only one machining operation on a race block, it would be to align-bore the main journals. If a cylinder isn't bored and left out of round, it will only make the engine run poorly, he explains, but if the mains are out of alignment, it's an invitation for a blown engine.

Stock rods use a press fit to hold wristpins in position. This requires heating the small end of the rod to get it to expand enough to fit over the wristpin. There are electric fixtures for doing this, but most engine builders simply use a torch. This may appear to be simple and something you can do at home, but we don't recommend it. Beyond the safety and fire issues, the wristpin (with the piston installed) must be centered over the rod before the assembly cools and everything hangs up. Needless to say, it's a lot easier said than done.

Once the rod is properly sized, you can take it away. To make sure the rod bolts are properly seated, most bolt manufacturers recommend that you torque the rod caps to the rods three times before assembly.

To get the proper torque specs, the rod bolts must be lubricated. Some manufacturers, such as ARP, provide their own moly-based lubricant. Others specify a certain type of oil. Because it can affect the torque value that you get, make sure you use what the manufacturer recommends.

Troutman puts the rod bearings into place. After this step, make sure you check the clearance between the rod bearing and the journal with the rods properly torqued. You can do this either with a dial bore gauge or Plastigauge. The dial bore gauge is vastly more precise than Plastigauge, so if you plan to assemble more than one engine in your lifetime, it's probably worth the investment.

After putting assembly lubricant on both the cam bearings and the cam lobes, slide the camshaft into place. Be careful not to bang the cam around in the engine, as either a chip on the lobe or a scratched cam bearing can spell trouble.