A filleted crank needs chamfered bearings.
Street and race engines receive basically the same machining processes, but race engines are often cut to a zero deck height meaning the top of each deck is milled flat in relation to the top of the piston at top dead center (TDC). Minimal gap between the top of the engine block and the top of the pistons ensures maximum compression. Also, race engines are finish-honed with finer stones, leaving a smoother finish on the cylinder walls than a typical street hone. This means less friction against the piston rings but more oil consumption-usually not good for a street engine.
Johnson says an often overlooked path to more horsepower is to install a deep-sump oil pan that includes some kind of windage tray. Keeping the spinning crank from dipping into the oil allows the crank to rotate more freely, reduces turbulence in the crankcase, and prevents aeration and foaming in the oil, which can starve the oil pump and cause a drop in oil pressure.
Finally, one of Johnson's requirements is an accurate timing pointer. "You can't be sure the stock one is in the right place or if the mark on the balancer is correct. The best thing is to make your own while the cylinder heads are off. That way, you know exactly where TDC for cylinder No. 1 is." Simple enough. This takes all the guesswork out of setting the timing accurately.
Also, while assembling the engine, be sure to use a good assembly lube. The guys at JMS use Isky Rev-Lube on the cam and lifters and Godson First Lube FL-128 on everything else. "It protects during start-up, and it clings well and doesn't coagulate while the engine is in storage," Johnson says.
Crank
We all know a forged crank is stronger than a cast crank and a billet crank is the top-self, bench builder part, but most street engines can get by with a stock crank, which is typically cast out of steel or nodular iron. A good place to spend your money is on a crankshaft with filleted journals. A fillet is a slight radius rolled between the journal and the webbing of the crank throws. A sharp, 90-degree edge is a prime target for stress risers to form, which can eventually lead to failure at that location. A filleted crank needs special bearings. These chamfered bearings have a beveled cut made along their outside edges to fit the fillets on the crank, so be sure to match the correct bearings to your crankshaft.
Stock rods versus aftermarket.
JMS likes to make its rotating assemblies internally balanced whenever possible. "It's better to keep balance weight off the ends of the crank," Johnson says. "Plus, the customer can use any neutral balance flywheel and damper."
Finally, Johnson tells us he likes to machine the main and rod clearances in a street engine to 0.002 inch versus a race engine that gets a slightly looser 0.003-inch clearance.
Rods
In most cases, you can reuse your stock rods. Johnson tells us aftermarket rods are a relatively new speed part. "Back in the '70s, all we had to work with were either stock rods, or we could buy aluminum or Carrillo rods-and those were considered race only. We made lots of power with stock rods." If you are using a power-adder or plan to rev the engine more than 6,500 rpm, however, you should consider forged rods.
When you are selecting a rod for a power-adder or rpm engine, piston speed is the issue. Take an engine with a 3.75-inch stroke. For one complete revolution of the crankshaft, the piston is traveling 7.5 inches from the top to the bottom of the bore and back to the top again. At 6,000 rpm, the piston is traveling 45,000 inches or 3,750 feet per minute.
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