Begin engine tuning with proper break-in. Regardless of what type of cam you have (roller or fl at-tappet), the rules of proper break-in apply to every type of engine because you want to seat rings and bearings with a proper run-in. When the engine fires, confirm oil pressure and take it immediately to 2,500 rpm and let it run at that speed for at least 30 minutes. The best scenario is to fire the engine on a dyno with an experienced dyno operator and run it in under a load after it has been running at 2,500 rpm for 30 minutes. For good piston ring seating, you want a load at 2,500 to 3,000 rpm. Loading with throttle builds cylinder pressure. Cylinder pressure allows rings to expand and seat into cylinder walls once the oil is at operating temperature.
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If you have dyno access, you can break-in an engine with proper tuning and operation so all you have to do is install it in the car. Dyno time begins with that good warmup at 2,500 rpm for 30 minutes to get the oil hot (minimum 140 degrees F).
The first pull you make is called a jet check. To perform a jet check, load the engine and go wide-open throttle for 15 seconds at 4,500 rpm and immediately shut down. Pull all eight spark plugs and inspect them. All the basic rules of spark plug reading apply here: tan/beige, you’re good; sooty black, rich; snow white, lean. If you see tiny dots of aluminum on the insulator, you are dangerously lean. When you are lean, go up several jet sizes bordering on rich, then come back in small steps and observe spark plug color. Spark plug insulator color is the best barometer of engine health and spirit.
Resist the desire to push ignition timing too far ahead. Start out in the 34- to 36-BTDC range and watch your power curve. No matter what anyone tells you, no more than 36 to 38 BTDC above 3,500 rpm. Testing under the controlled conditions of a dyno room is one thing; on the road with 92-octane fuel in a hot engine compartment under varying conditions is another thing entirely. Pin the throttle and trash your new dyno-tested engine in short order because you’re too lean or ignition timing is too far ahead. Be conservative and keep it in one piece.
Written by George Reid and Republished with Permission of CarTech Inc