This may sound like a simple question, but what is cylinder wall glazing and how is it created? I hear about it all the time when people talk about piston rings not sealing, but I’m not sure what it really is. Thanks. – T.D.
Jeff Smith: Great question! We did a little digging and then called Keith Jones at Total Seal for a quick education.
Two types of distress can victimize the cylinder wall, Jones said.
Let’s start with glazing.
If you use a microscope to look at a side view of a freshly honed cylinder wall, it might look a little like a hash of sharp lines like those earthquake seismograph plots that Californians are conditioned to viewing on TV.
The idea behind creating the proper honing pattern is to create a series of peaks and valleys. The valleys are the most important since they hold the oil that eventually lubes the cylinder wall. The peaks also need to be there to eventually break in the rings, but the latest trend now is to reduce their height to improve ultimate sealing.
The break-in process is extremely important to make sure the rings fully seat to the cylinder wall and that a portion of those peaks remain. Jones said the engine should not be idled for more than 10 or 15 minutes and even during this time the engine speed should be varied.
“I hate run-in stands, Jones said. “I really don’t like them because they don’t put any load on the engine.”
The key to ensuring that the rings break-in properly is to put a load on the rings as soon as the engine has achieved its normal coolant and oil temperature, he said.
If you’re on the dyno, put progressive load on the engine starting at 50 percent and quickly moving to 100 percent. With the engine in the car, this means 10 minutes of idle or less to get the coolant temperature up and then go out and begin light acceleration runs quickly followed by eventual wide-open-throttle (WOT) accelerations. It’s likely the rings will be seated even before you get to the WOT runs.
This approach is for a typical street engine using moly-faced rings, which would be the majority.
Race engines with nitride steel rings use a different, courser finish for honing and may take slightly longer to seat, but the process won’t take days or even hours.
Problems can occur when the engine is lightly loaded or idled for long periods after the first startup.
“Never idle a brand new engine for an hour with no load,” Jones said.
Doing so can create a glazed cylinder wall.
Glazing is essentially combusted oil residue and carbon that remains on the cylinder wall and eventually builds up to a wet, shiny look on the cylinder wall. It almost looks like the cylinder wall has been painted with a clear paint job, Jones said. This finish occurs when the oil fills in all those valleys, creating a very smooth surface on the cylinder wall because no load was applied to peel the oil off of the wall.
This glazing makes the job of removing oil from the cylinder wall nearly impossible. The buildup will continue and eventually you will likely see a bluish haze coming from the exhaust.
With no load on the rings to remove this coating, it continues to build and if allowed to go on too long, will pile up enough that it turns yellow and creates a hard layer that makes oil control nearly impossible even with undamaged rings.
Possible Solutions to Cylinder Wall Glazing
While many sources claim that this will require re-honing, Jones said there are possible solutions to consider first.
There are some top-end cleaners such as SeaFoam engine cleaner treatment that can be poured directly down the carburetor or inlet tract on an EFI engine to help clean the cylinder walls.
The best stuff he has ever tried, Jones said, was a GM top-end cleaner that is no longer on the market. There’s no guarantee that the current cleaners will do the job but a combination of high load and a top-end cleaner might be able to reduce the glazing and allow the rings to seat.
Burnishing: Even Worse than Glazing
An even-worse condition is called burnishing.
This occurs when engines are run with excessive rich air-fuel ratios and no load.
Jones has seen several examples of engines with 9.5:1 to 10:1 air-fuel ratios that idled for long periods with no load. When this occurs, excess fuel washes the oil from the cylinder walls and essentially peels the top peaks over into the adjacent valleys.
When this happens “the cylinder wall gets very dark in color. Like a dark grey—almost black,” Jones said.
The only correct solution for burnishing is to disassemble the engine and re-hone the cylinder walls.
So the obvious message here is to properly break in the engine using high quality lubricants designed specifically for engine break-in.
There are dozens of boutique engine break-in oils and several companies, like Driven Racing Oil, offer different styles based on viscosity and application.
It would take perhaps an entire story on all the different break-in oils and why each has a place, but perhaps among the important points is that sufficient levels of high-pressure lubricants like zinc dialkyldithiophosphate (ZDDP) is more important for proper break-in of a flat tappet cam than for ring break-in. In fact, levels in excess of 1,500 to 2,000 parts-per-million (ppm) of ZDDP can contribute to cylinder wall glazing—especially if this oil is combined with excessive engine idling for an excessive period of time.
So be careful because too much of a good thing like ZDDP can create poor results.
To prevent cylinder glazing or the even-worse condition of burnishing, it’s best to use high-quality break-in oil, be spot on with the part throttle idle air-fuel ratio and ignition timing, and don’t idle the engine without load for more than 15 minutes and vary the rpm during this time by constantly spinning the engine up to 1,500 to 2,000 rpm. Apply a load to the engine as quickly as possible. Then drain the break-in oil after 100 miles or so and go directly to the long-term oil you intend to run. All that will contribute to a well-sealed engine that will likely perform up to your expectations.