The internal combustion engine may have been man’s greatest creation. It’s powered us across land, seas and skies. And over the past 220-or-so years, these controlled explosions have exponentially increased in power and efficiency. Advances in engineering and machining have helped the ICE become more powerful and efficient as it has developed. Still, when slamming an engine back together with factory specs or stuffing an engine with lots of exotic performance parts, the right break-in procedure helps keep those precise measurements in check.
Tighter tolerances, smoother surfaces and smaller gaps lead to more power and less wear. And if you spent a ton of money building up your hot rod, the last thing you want is for it to lose power because of a bad break-in.
A line of V6 engines at the Iwaki Plant of Japan’s Nissan Motor Co. in Iwaki, f*ckushima.
For starters, you need a place to start your engine. If you don't have a handy engine stand in a dynamometer cell, you can always put together your own run-in stand (though if you're like us, you'll probably just install your freshly rebuilt engine into its future home). Making sure you have simple but essential gauges for oil pressure and coolant temperature will help you know if you did anything catastrophically wrong. Hooking it up to an exhaust system will help you hear if one of your rod bearings is eating itself or if you have valves slapping pistons.
Now is also a time to make a good visual inspection. The folks over at MAPerformance recommend “thoroughly inspecting ALL of the moving parts you’ve touched during installation,” along with all of your fluids.
Fluids—namely oil—is one of those hot-button issues over which we’ll probably never reach a consensus. But it’s best you follow whatever your camshaft or valvetrain component supplier recommends. For instance, if you're using a flat-tappet camshaft, you should probably lean on a healthy dose of ZDDP, but, again, your camshaft supplier should offer break-in instructions. An area where everyone does agree: priming the system. If you can, priming your oil pump and feeding oil throughout the engine will help prevent excessive wear from dry running. Yes, you should have oil and assembly lube already in place on your wear components, but it's still good practice. And change your oil early and often, like after initial break-in, at 500 miles, 1,500 miles and 4,000 miles.
A rudimentary engine cooling setup.
If you’re running a flat tappet, run the engine between 2,000 and 2,500 rpm with no load on the engine for the first 30 minutes, according to Summit Racing. Let the engine cool down completely and repeat the process two-three more times. “Do not idle the engine for any extended period at this time. This is critical to break in the camshaft.” Roller cam engines do not require this procedure.
An engine needs to build up cylinder pressure to expand the piston rings and allow them to seat. Failure results in poor performance and blow by (high pressure on the top side of the piston pushes combustion gasses, as well as droplets of oil and fuel, past the piston rings and into the crankcase).
Once you’re finally rolling out of the garage, drive the vehicle at varying speeds and loads for the first 200 miles, according to ATK. Occasional full-throttle runs from a rolling start will help seat the rings. We said occasional! After 200 miles check the rockers/valve clearance and retorque the head bolts and intake manifold bolts.
My 1963 Pontiac Star Chief, named Big Rhonda.
If you want to be extra gentle, after 200 miles do five or six medium-throttle accelerations, a couple hard throttle accelerations and coast back to about 20 mph. From 500 to 1,000 miles, drive normally but keep rpm below 5,000. Always avoid long periods of idling during this time, says Summit.
It’s all a pain in the you-know-what. But it’s only 1,000-1,500 miles, and if you want to go 100,000 or 150,000 miles on your rebuilt or built-up motor, it’s a small price to pay. And your engine internals will thank you for it. Tolerance!
Jake Lingeman
Jake Lingeman has been with Autoweek since 2006 and career highlights include driving the Silverstone Circuit in England, taking the Corvette ZR1 around Road Atlanta and going to the 24 Hours of Le Mans. When he’s not writing about, driving, working on or thinking about cars, he’s reading liberal books and playing video games. In his opinion, the best new car in the world is the Ferrari 488 Pista. The Ford Shelby GT350, the Nissan GT-R and the Porsche 911 GT3 are favorites too. He owns a 1963 Pontiac Star Chief, a 2014 Ford Mustang GT and 1989 Mercedes-Benz 560SEL.
