By John Machaqueiro Images by THE AUTHOR

n the automotive restoration game, there are a wide range of options when it comes to tackling the various processes involved. What defines a restoration can also be interpreted in many degrees. There are several variables that come into play, and for places that are doing high-end concours restorations the need to bring a car back to how it rolled off the assembly line is the bar that is always set and challenge always faced. Knowledge of the correct finishes on the various parts found on a given vehicle require a certain level of knowledge and experience in their application. Painted items are one part of that equation, however, the range of different bare metal items found on a vehicle usually requires a different approach when it comes to their restoration. The easy path sometimes is to simply find a mint N.O.S. replacement, but that is not always an option. When it comes to aluminum parts, there are various ways that shops tackle their restorations in what they deem as the best solution. We’re going to exclusively focus on aluminum parts, and we have the perfect test subject: an L78 intake manifold for a 1965 Corvette that was recently vapor honed at American Muscle Car Restorations (AMCR) in North Kingstown, Rhode Island. They have over the years set the bar to the highest level with many award-winning OEM restorations under their belt. Vapor honing is another tool that they have added to their arsenal of processes that we will be testing on our manifold.

You might be asking, ‘What is vapor honing?’ You may have heard of it also referred to as wet blasting or slurry blasting. By whatever name you’re familiar with, it is a process that utilizes a mixture of abrasive media, water, and compressed air to clean, polish, deburr, or finish a surface. The choice of abrasive media is critical and depends on the material of the workpiece and the desired finish.

For an aluminum part that is going to be used in an OEM restoration, getting it back to original condition with the correct finish is the desired outcome. The folks at AMCR have switched over to this vapor honing technology to restore aluminum parts, however, prior to the use of this procedure they were getting the same results from a 10-step process that they had developed and perfected. This single-step switch has allowed them to significantly reduce the overall time spent on a given part while still achieving the same results.

The end result with these parts and the reduction in time translates to less manhours used and a cost savings for their clients.

1-2. The starting point on this intake prior to placing it in the cabinet to vapor hone was to make sure that it was completely clean and free from any grease. We also did a repair to the rear mounting tab prior to any effort at cleaning. There are some other material issues that we will cover to further facilitate in the process. It is important to ensure on a part like an intake that all surfaces (top and bottom) are grease-free. This will preserve the longevity of the blasting media by reducing contamination. If there is any significant buildup inside the runners the most effective solution is to have the intake hot tanked prior to any vapor honing. This is accomplished by placing the part in a tank filled with a heated, aluminum-safe chemical solution designed to break down carbon, oil, and grime. The solution must be non-caustic or specifically formulated for aluminum to avoid corrosion or pitting. Our test subject had very clear runners with no substantial buildup.

4. Having a clean grease-free surface is fundamental in extending the lifespan of the honing media. On items like intakes, they were often in place when folks painted their engines so overspray ended up on the outer edges, or in some cases the entire manifold. Depending on the amount and thickness of the paint, it is usually a good idea to remove it before vapor honing. One of the most sensible ways if someone is not having a part hot tanked is to chemically strip and remove the paint with a nylon brush, which will not harm the texture of the aluminum surface. The rear section on our intake had some paint, and we opted not to remove it because it was borderline acceptable for the media we would be using.

6. Areas where some rust is present as a result of the galvanic corrosion that takes place when aluminum and steel are in contact with each other was also addressed in the vapor honing process.

8. Because AMCR is exclusively using this process for aluminum restoration, they have opted for glass beads as the abrasive material that best suits that task. Glass beads are non-aggressive and spherical in shape. They clean by impacting and gently removing oxidation, surface dirt, grease, corrosion, or light rust. Glass beads are usually graded by mesh size, which refers to how many openings per inch are in the screen used to sort them. They come in four different grades with the one that AMCR opted to use falling under the very fine/micro finish grade with a mesh size in the 170-325 range. Their size is measured in microns. This grade of beads comes in at a ~90 – 45 µm micron size range, which is ideal for polishing, very light cleaning, and fine detailing that will leave parts with a natural satin or matte finish. The glass beads are sourced from VHT along with the Anti-Microbial Agent that is mixed with the water to minimize the development of fungus from sitting or processing certain parts.

10. With the intake placed inside the cabinet it illustrates the size of the workspace that is available. This is the ideal size for a shop that is dealing with aluminum parts generally found on a car.

12. The end result of our effort is a part that is restored back to its fresh cast looked. The process of cleaning this part from start to finish took about 40 minutes. This time will vary depending on the size of the part, the amount of cleaning required, and the complexity of the casting.

14. This area was lightly painted and vapor honing effectively removed the engine paint. Because of the gentle nature of this process there is no difference in the texture of the finish achieved. The question you might have is if there is any material removed. There is some material that is removed during the vapor honing process, but it is at the micron level. Other types of more aggressive media will significantly remove more material, which will lead to the altering of the original texture of the part. With an OEM restoration, that texture is one of the key elements to preserve.

15-16. These two images illustrate the harder-to-reach areas on this manifold. The runners and plenum opening were also honed and the layer of carbon deposits removed.

17. This image illustrates the need to have repairs done prior to any type of cleaning. If the repair is properly done and cleanly blends in with the surrounding material, once the part is cleaned it will blend in seamlessly with the rest of the finish.