Cleaning

By Charles Navarro

We’ve all heard the saying, “Cleanliness is next to Godliness.” Same holds true when building an engine. Using the best quality parts and the proper break-in oil doesn’t necessarily guarantee satisfactory results with a new engine. I hate to have to rely on cliché sayings, but another great one that is equally applicable to this discussion is “trust but verify.”

As both a parts manufacturer and as well as a reseller of engine components, half our battle in this day and age is making sure the parts are made correctly and unfortunately, quality control in a post-COVID era has slipped, requiring the engine builder to pick up the slack. As a manufacturer, we have extensive quality control and check 100% of everything we make, however the same can’t be said for all suppliers.

Read this article with all images in the digital issue of Engine Professional magazine https://engineprofessional.com/2024EPQ3/#p=44

However it just doesn’t stop at measuring components. As mentioned already, you can use the best parts and still have poor results from an engine rebuild. The common denominator we see with most failures is lack of proper preparation, namely cleaning parts. If you poll most top engine builders, building the engine isn’t the most time-consuming part of the whole process. Measuring all the parts and preparing them for assembly, including cleaning, usually is the hard part. Also, over the years, I have visited some shops that do not have a dedicated clean room for carrying out this work. I remember years ago visiting a dealership and seeing an engine being built up in the same area where they were turning brake rotors. This is often the norm, not the exception.

Many shops, ours included, have seen the benefits of using ultrasonic cleaners, but this alone is not sufficient for cleaning engine parts. Most of the highly effective cleaning products we previously had access to just don’t exist or are not sold in every state or country. For many years, denatured alcohol has been our go to, especially when used in conjunction with white lint-free wipes, like Kimwipes. The idea there is to clean parts until the wipe comes out as white as it went in. But sometimes we have found that this simply isn’t enough.

Case in point is with cylinder bores. We all know that it’s critical to use a profilometer to verify the surface finishes on a cylinder bore so you know they are correct, however most people when asked aren’t doing much more than wiping the bore out before doing a trace when checking their work. We’ve found if you properly clean the cylinder bores after honing, but before using the profilometer, you will most often get totally different readings. The valleys tend to trap debris, resulting in incorrect surface values. In some instances, we’ve also seen where during honing, material can be folded over rather than be removed, again giving false readings for RpK and RvK values, until the cylinder bores have been cleaned with some sort of mechanical agitation. It is this contamination that causes most of the cylinder bore and piston wear on a freshly rebuilt engine. We work almost exclusive with Nikasil plated cylinder bores, so it’s even more important to make sure this honing debris is removed. Although cylinder bores may appear to be clean, the nickel, silicon, and carbide remnants are extremely abrasive and will cause significant damage to pistons, rings, and cylinder bores if not removed, requiring cylinders to be stripped and re-plated and pistons to be replaced, resulting in costly repairs.

We’ve found that the best way to accomplish this is good old elbow grease coupled with ATF. As a manufacturer of Nikasil cylinders, we introduced a process where we use automotive grade red Scotch-Brite pads loaded into a mandrel that allows us to scrub the cylinder bores aggressively while providing a constant flow of ATF to the cylinder. What would normally take hours by hand, we accomplish in about two minutes per cylinder bore, along with changing out the Scotch-Brite pad between cylinders to ensure the process works consistently. Some of you might already use plateau brushes after honing iron or steel bores, which is attempting to achieve a similar effect, however we found the these brushes, unlike on steel or cast iron bores, had little to no effect on Nikasil cylinders. Some have reported using Marvel Mystery Oil in place of ATF successfully while using white microfiber towels to scrub the bores, but regardless of which process above is used, a final cleaning with denatured alcohol and Kimwipes is recommended.

When cleaning the cylinder bores, you know they are clean when the surface finish values no longer change. We adjusted our process based on how much time we found was needed using our mechanical cleaning, but if you are doing this by hand, be forewarned this could take hours. We’ve been able to quantify cylinder bore cleanliness by using a microscope to inspect the honed surface, as you can visually see the folded over material and contamination on the peaks and in the valleys that normally aren’t visible with your naked eye.

This same process can be used to deglaze a used Nikasil plated cylinder, but before reusing any Nikasil cylinder it is important to make sure there is no damage you can catch with your fingernail or physical damage such as chips or adhesion related issues, and that the cylinder is in specification for ovality and taper. Cylinders that are out of round or are damaged cannot be re-honed without resulting in excessive piston to cylinder clearance, so if the cylinder is a good candidate for reconditioning, re-plating is the best option. Besides comparing the surface finishes both in and out of ring travel to evaluate cylinder wear, on air-cooled cylinders we also check hardness against a known good cylinder to ensure the engine had not been overheated. Often cylinders that are out of round or beyond their service life will measure soft and are not suitable candidates for reuse, even with re-plating.

Those of you who work with engines that have Nikasil bores are probably all too aware of streaking that commonly occurs to cylinder bores during break-in. Although the type of piston ring, coatings, and ring tension do factor into this, we’ve found that the extra time and effort that goes into cleaning the cylinder bores will result not only in better ring seal and less oil consumption, but also less cylinder bore streaking.

Not measuring your engine components and thoroughly cleaning them during the assembly process is a recipe for disaster. Assume nothing and quantify everything.
“You can’t rush success but you can definitely rush failure.” Attempting to achieve success through shortcuts or without proper preparation will often lead to failure. Engine building is no exception.

Read this article with all images in the digital issue of Engine Professional magazine https://engineprofessional.com/2024EPQ3/#p=44