Breakin-In Is Hard To Do - Engine Builder Magazine

Breakin-In Is Hard To Do

Heavy greases offer the best protection for cam lobes and flat tappets in new engines. Grease will stay on a cam lobe indefinitely, and oil will be released from the grease only when it is required.
Heavy greases offer the best protection for cam lobes and flat tappets in new engines. Grease will stay on a cam lobe indefinitely, and oil will be released from the grease only when it is required.

Before we begin discussing assembly lubes and break-in oils, I would like to emphasize that no one factor is responsible for racing success (or failure). It’s like an algebraic equation with a lot of variables, all of which must be addressed.

The same is true of engine assembly and break-in. You must utilize only those parts which have worked best for you and machine components such as cylinder walls to the proper specifications before you consider whether or not to use specific break-in oils and assembly lubes.

A significant mistake in any of these areas, and the game is over. I say this, because I’ve discovered the ‘fatigue limits’ of a number of engines simply by not paying attention to ALL the variables. That’s called experience, and most of us gain it the hard way.

To illustrate this point, look at the accompanying photos provided by Jerry McLain of McLain’s Automotive Machine Shop in Cuba, MO. This small block was completely worn out after only a few hundred miles. Upon teardown and inspection, Jerry noticed that the cylinder walls had received only a light honing after the boring bar passed through the bores. Do not shortcut the honing process. Jerry says the better engine builders spend hours honing a block, not minutes. Or, as he puts it, “Honing is also part of the break-in process.”

Jerry says after every machining operation, the parts must be meticulously cleaned to remove aggressive metal shavings and abrasive grinding stone debris. I once inspected an engine that was totally worn out in 90 miles.

The engine builder had glass beaded many parts including the intake manifold, but he failed to remove the tin heat shield on the bottom of the intake to remove all the glass beading debris. When the engine was started, the vibration caused debris to fall out of the intake into the crankcase. Abrasive debris such as this doesn’t care what it cuts – it will cut piston rings just as fast as anything else.

Years ago, racers could only use those engine oils that were provided by the major motor oil marketers. Since racing was such a small portion of their overall businesses, oil marketers seldom provided any specialized products. When they did those products usually weren’t based on sound research and development.

We now have a plethora of racing oil suppliers, and considerable research and development has been performed to determine exactly what oil characteristics racing engines prefer. Let’s eliminate blown alcohol and nitro methane fueled engines from this discussion, because their major issue is durability, not the production of horsepower. Those engines require very different properties from their lubricating oils.

Gasoline and naturally aspirated alcohol-fueled engines have two distinct lubrication requirements that separate them from typical passenger car engines. Racing engines need additional protection from cam and lifter failures and optimized piston ring and cylinder wall sealing.

Cam and lifter protection is primarily needed by these racers running flat tappet camshafts. Roller cams are more forgiving if their needle bearings are properly lubricated, but extreme cam profiles have been known to burn up pushrod tips on roller cam engines if sufficient EP lubrication wasn’t available. The main things to remember here are that flat tappet cams and lifters (and pushrod tips) essentially need three things from a lubricant:

• First, cam lobes and lifters (and roller bearings) must never be allowed to run dry. As soon as metal-to-metal contact occurs, a part is forever altered, and destruction is the end result. Early cam and lifter lubes were liquid because cam manufacturers only wanted one product for both cam and lifters and cam bearings.

Occasional cam and lifter failures were observed when cam lobes either weren’t adequately lubricated or engines were stored for considerable length of time. Remember, establishing oil pressure throughout the engine prior to first startup does nothing for most cam lobes and lifters, because they are usually lubricated by splash only after the engine is operating above idle speeds.

Heavy greases offer the best protection for cam lobes and flat tappets in new engines. Grease will stay on a cam lobe indefinitely, and oil will be released from the grease only when it is required. Remember, grease is essentially oil encapsulated in a soap matrix to keep the oil from flowing away from the part being lubricated. When the grease gets hot enough, it will release the oil to flow to the part and lubricate it. Cam journals are, of course, lubricated by pressurized oil.

• Second, cam lobes and flat tappets need sufficient zinc dithiophosphate (ZDP or ZDDP) in the oil to form a sacrificial film on the lifter and cam lobe surfaces preventing metal-to-metal contact with extreme valve spring pressures (EP protection). Modern passenger car engine oils contain less than half as much ZDP as is needed. Racing oils utilize increased ZDP levels in their formulations. You can add ZDP to your existing oil, but how do you know you’re adding the right amount at the right temperature?

• Third, cam lobes and flat tappets need oil to allow only sufficient wear to remove roughness inherent to machining practices and properly mate the surfaces to each other. Flat tappets are machined slightly convex (the center is highest) and cam lobes are machined slightly tapered to cause the lifters to rotate. Excessive wear causes these surfaces to flatten, and lifter rotation stops. When lifters don’t rotate, they soon fail.

Mineral oil-based racing oils do a good job of providing a reasonable wear rate to facilitate break-in. Synthetic oils, however, sometimes tend to slow the break-in rate because of their inherently lower friction. To ensure that break-in is being accomplished quickly and safely, I use only break-in oils.

Now to the production of horsepower! Ask any competent engine builder, and he will tell you that optimum ring and cylinder wall sealing is essential to the production of maximum horsepower. Notice how many serious racers check cranking compression pressures and cylinder leak-down rates prior to that big race.

When I was doing R&D for several  head engine builders in NASCAR and NHRA, I was often asked, “What can you do with the oil to improve piston ring sealing?” The engine builder can do everything he knows how to do to have the perfect surface finish on the cylinder walls, but the piston rings must correctly mate to those walls to optimize cylinder sealing.

To optimize ring and cylinder sealing as rapidly and safely as possible, use break-in oils specifically formulated for this purpose. Break-in oils are formulated to allow more rapid mating of the rings to the cylinder walls. Sure, you can break the rings in without using break-in oils, but it will take longer to do it.

Remember, the better the oil is for durability, the worse it should be for break-in. Also avoid highly friction-modified oils until after the engine is completely broken in. We will discuss the horsepower benefits of highly friction modified oils at another time.

A few years ago Daimler-Benz was having trouble breaking in their large diesels when using very highly compounded synthetic diesel engine oils. We tore down and inspected some of these engines after a few hours of operation and observed a “glazing” of the cylinder liners mid-way down the bore where piston speeds were highest.

The rings were literally sliding over the tops of the honing pattern and not removing asperities. Metal filings and other debris were literally filling in the low spots. The solution was to provide each Mercedes factory with a break-in oil designed to be used for the first oil change interval.

In conclusion, I use break-in oils to seat piston rings and cams and lifters as quickly as possible without engine damage. I realize we’ve all done it other ways in the past, but now we have the technology to do it correctly and safely.

John Martin is a “motorhead” physicist who worked for Lubrizol for 25 years, and before that he worked for Shell. He has formulated and tested racing oils for NASCAR and NHRA Pro Stock engines for decades. He has 22 patents to his credit through his work on engine and driveline testing and optimization. He is currently building a fuel-injected 692 big block Chevy for his street rod.

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