As much as we love exhaust headers, many folks stick with original cast iron manifolds when performing a restoration. The problem with bare cast iron, however, is that it never looks as nice as when it’s fresh. While generally durable, it eventually flash-rusts on the outside, bringing down the appearance of an otherwise top-notch restoration.
Some cast iron parts can be painted; think about differential housings and brake calipers, for instance. But when it comes to exhaust manifolds, their continuous exposure to heat generally rules out most paints. So how do you get good-looking manifolds that don’t require constant attention?
There are two dependable solutions that make cast iron manifolds look great without a lot of maintenance. The first is Calyx, a paste-like treatment that gets rubbed into the bare metal. The second is a specially developed high-temperature paint that replicates the natural look of cast iron when cured.
We decided to test the two different finishes side-by-side to see which looks most natural. Using the stock manifolds from our Range Rover project, we spent some time at the blast cabinet to get the rust off. Satisfied with how the parts looked in bare form, we moved on to refinishing them.
Calyx Treatment
If you had to describe Calyx to someone quickly, you could say it’s like a shoe polish but for metal. The small container of metallic paste (just 2.75 ounces) is enough material to coat as many as four manifolds. You can apply it with a small brush, a rag, or even your fingertips, working the material into the part. As a dressing, you simply wipe off any excess after application, then cure with heat by running the engine.
The beauty of Calyx is you can apply it with the manifolds in place, even going over rust if necessary. We preferred to work it into the bare iron, however, since we had the manifolds off the engine for a rebuild anyway. Still, this ability to do touch-up in place is a great advantage when preparing a vehicle for show.
We used a shop rag to apply Calyx to one of our manifolds. The process wash quick, taking only a few minutes once the part was blasted and wiped clean with prep solvent. Since the engine will not be running any time soon, we chose to set the treatment temporarily. Thirty minutes in a small oven (in this case, our benchtop powder coating oven) at 300º seemed adequate.
The resulting finish looks natural and very consistent, if slightly darker than the bare iron. All the casting marks and details came through perfectly, as well. All told, this is a great-looking finish that would look right under the hood.
Eastwood Factory Grey High Temp Coating
We turned next to Eastwood’s Factory Grey High Temp Coating. This is a direct-to-metal spray paint that also fully cures using the heat of the engine. Once cured, it’s resistant to damage or discoloration up to 1400º F, which should be more than enough for anyone. This finish can also be sprayed over existing rust, but it works best on bare metal.
Once again, we blasted and degreased the manifold to get down to clean metal. Painting this finish is no different than any other spray paint, but it will run easily if applied too heavily. We had a couple runs on the initial spray out, although they eventually settled and blended when dry.
Most engine paints tend to bury the texture of cast metal parts, leaving them too smooth and shiny. The High Temp Coating dries down surprisingly thin, preserving the original look. The color also looks natural and has the right degree of metallic sparkle to match cast iron.
Decision Time
To be honest, both the refinished manifolds look great on their own. The High Temp Coating looks surprisingly more accurate, color wise, than the Calyx, but only slightly. The Calyx-finished manifold looks like it just came out of the foundry with a more porous texture, however.
If you have a show-worthy machine and you’re looking for a little “pop” under the hood, the High Temp Coating may be your preference. For the sake of our Range Rover project, we’ll probably end up treating both manifolds with Calyx. The ability to re-dress the parts later when everything is reassembled has us leaning that way. Either way, both finishes look great and will make the ugliest part of your engine look like new.
Hi. I am still partial to the grey high temp coating mixed with a little of the same black high temp coating to darken the gray up a little. By darkening it up and having a custom mix, the manifold looks like it just fell out of the foundry and it won’t be the same color gray or black as your neighbors at a car show making you look like you both used the same thing. I love this stuff. I have been doing this trick with Eastwood stuff for 30 years plus. Restoration in a can applied with the worlds cheapest sponge brush so I can throw away the brush because this stuff is tough enough you will never clean out the brush. Party on.
We’ve offered both these products for a long time. As with anything, prep matters a lot. The ability to blast these parts back to bare iron will help both finishes be more durable.
Historically, the paint has held up well on bare metal, less durable when painted on top of rust. It has s a high metallic content and was developed for temps up to 1400 degrees. It doesn’t really flake off as much as wear thin or take damage from underneath.
The Calyx being a dressing, it’s somewhat more susceptible to aging. The beauty of it is that you can reapply it easily when it starts to show wear through. A professional concours detailer we know uses Calyx on all his customers’ cast iron manifolds and they always look great on the show field.
Yes I agree with Jeff. We would like to see the long term effects of heat cycling. Please post an update after this vehicle is done, driven and parked a number of times.
Exactly, which one will rust first ?
Answer the REAL question please!
But which one will hold up better to heat and over time?