Pierce-Arrow Society Feature Article
Coating and Repair Options for your Pierce-Arrow Manifolds
by Chris Diekman
The ‘31 Model 43 Pierce-Arrow’s previous owner had the manifold set porcelainized in shiny black, but brittle porcelain, sometimes referred to as “vitreous enamel”. He spoke with pride that he had gotten the Pierce to his first PAS Annual Meet before the porcelain had cracked. Porcelain, or vitreous enamel, was the original coating on the Pierce-Arrow 8 and 12 cylinder manifolds.
Indeed, it still looked great when we bought the car, but there were already hairline cracks in the porcelain along the length of the exhaust manifold and there were already dime size patches of the shiny porcelain missing along the top surface of the exhaust manifold between cylinder 3 & 4 and 5 & 6 and on the runners for 2 & 3 and 6 & 7. The bill for the porcelain coating came with the car’s notebook & records, and the porcelain coating had not been cheap!
As time marched on, many tours and car shows down the road, the intake manifold still looked good, but the exhaust manifold looked pretty shabby and forlorn. More black porcelain was missing, flaking off and laying in the splash pan. Softball sized mild orange and brown splashes of oxidized cast iron now emerged where the porcelain had lifted and flaked off and were much too evident for my liking. Thermal cycling of heating and cooling of the engine and subsequent expansion and contraction of the cast iron cracks the brittle porcelain coating, and it begins to flake off. As you may already know, this flaking condition gets much worse if your timing is retarded, your carburetor mixture is too lean, or your cooling system is not cooling the engine well enough. This drives more heat into the manifold, causing further thermal expansion, cracking, and de-lamination of the exhaust manifold porcelain.
Now, it is true that in judging, PAS, AACA, and CCCA do not really fault a car with point deductions for minor cracks or small areas of missing porcelain on the manifolds….as this is how it is. However, if large areas of porcelain are gone, some clubs will start to deduct points because it is getting too far from the judging standard of “new car condition”. Cars that are driven regularly and have some miles on them (other than just on and off the trailer at a show) will typically have various degrees of exhaust manifold finish problems. The intake manifold does not have to withstand the heat of the exhaust gases, so typically, the porcelain on the intake manifold holds up well. However, there is something about the Pierce 8 exhaust manifolds that develops hot spots on the porcelain and it fails fairly readily.
If your car is driven regularly to simply enjoy the marque and you are not concerned about showing your car, maybe the manifold finish is the least of your worries. Maybe you are more concerned with the function of your manifold, or perhaps it needs a crack in the casting repaired.
However, if you are in a car show, especially at a Concours d’Elegance, and you are parked next to a car in your class that has flawless manifolds it could mean the difference between winning and losing your class. Having nice looking manifolds is an intangible that gives your car a little “extra” appearance or quality aspect that for otherwise equivalent cars, could tip the balance. That is fine, too. I just like to have a nice clean look under the hood. In any case, I thought that my case study might be helpful to other members so I thought I would share what I have learned over the last few months in this article.
In looking through options to provide a satisfactory finish for the manifolds on the Pierce, I gathered some basic information. When my manifold set was restored the first time, it was done by Prairie Auto Porcelain in Faribault, Minnesota (PH. 507-645-5325). This is a very reputable firm and they have been doing this kind of work for many years. Porcelain-izing is also known as “glassing” and consists of baking the coating onto sandblasted and cleaned cast iron manifolds at about 1500 degrees F. It results in a glassy smooth and glossy finish. A good porcelain job does look nice! The problem is, on some engines, the porcelain is not very durable and does not hold up well. There are a number of variables here that affect the porcelain durability. Engine tuning is critical:
Higher exhaust temperatures result in more expansion and subsequent contraction of the cast iron manifold and causes cracking of the brittle porcelain coating. The porcelain has no elasticity and no ability to expand, so it cracks. If the manifold gets super hot…the coating material just lifts off due to the heat and falls into your lower splash aprons.
If you prefer that ultimate glossy look and insist on porcelain, one proactive thing that can be done is to media blast, clean, and coat the inside surface of the exhaust manifold with a ceramic coating. This reflects the heat away from the cast iron and promotes exhaust gas flow through to the exhaust system, reducing the temperature of the exhaust manifold. Depending on the actual exhaust gas temperature, test data indicates reductions of 100 to 130 degrees Fahrenheit reduction in radiated temperature on an internally coated exhaust manifold. Prairie Auto Porcelain is now able to provide internal ceramic coating with external porcelain on exhaust manifolds. Fellow PAS Member, Rick Horne, also recommended Custom Ceramic Coating in Lenzville, Illinois for porcelain coating. They did a 1929 Pierce exhaust manifold for him for a reasonable price of $550.
In all fairness, there are some engines that have no problem at all with the porcelain flaking off of the exhaust manifold. It depends on the engine, manifold design, how much the car is driven, and the tuning variables I mentioned earlier. However, having seen exhaust manifolds on other Pierce 8’s pretty consistently shedding porcelain, and with my experience on this particular Pierce-Arrow engine, coupled with the higher cost of porcelainizing ($1200-$1500 for the two manifolds), I chose not to do this again. I wanted the car to be drivable and NOT to have to do this re-coating again anytime soon.
I had also talked to another couple of fellow PAS Members. They had both recommended high temperature powder coating. I looked into this further. There are indeed special high temperature resistant powders that are good for 1000 degrees F or more. DuPont Alesta “Pipe Black” powder is representative: as an example is cured at 450-500 degrees F, and can withstand up to 1000 degrees F working temperatures. Pipe Black also gives a glossy finish and the brochure shows that it is used for barbecues and exhaust systems. These are not off-the-shelf powder materials and have to be specially ordered by the powder coater. Off-the-shelf powders are only good for 400-500 degrees F., which is way too low for exhaust manifolds and would just burn off right away.
However, some of the literature and chat room info does not recommend even the high temperature powders for exhaust header or exhaust manifold applications. Remember, these powders are essentially a plastic. While they can provide the desired glossy finish, they can get soft and start to lift and flake off of the cast iron at extended temperatures. A sampling of the bulletin boards on the Internet generally say that high temperature powder coating of the exhaust manifold works good on motorcycles and smaller displacement engines, but when you get into V8’s, like in a hot rod or muscle car, that even the high temperature powders do not hold up to their exhaust temperatures.
Now, you could argue that our low compression L-Head engines do not create high performance V8-like exhaust temperatures and that the high temperature powders should be sufficient. However, not wanting to do this recoating process a third time, and the engineer in me, I am looking for some additional margin of performance on temperature and more longevity on the exhaust manifold coating.
Jet Hot (Ceramics)
Peter Williams had recommended the “Jet Hot” brand of coating. Jet Hot advertises nationally, and have the higher temperature ceramic coatings. They offer:
As these are ceramic coatings, they do not really have a high “gloss” black and the Jet Hot website also advises that the higher temperature coatings they offer have a “gritty rough texture”. Peter has the “Extreme 1300” Jet Hot silver (1300 degree F rating) on his Series 80 manifold set and is happy with it. The service was quick and very competent and the price for the coating was reasonable at approximately $250 total for both manifolds (several years ago). Peter said that he would go back to them again.
However, Peter said after a few years of touring and car shows, the 1300 degree F (Fahrenheit) coating is showing some rust coming through the coating on the exhaust manifold.
It is hard to be precise as there are so many variables and conditions, but exhaust gas in an internal combustion gasoline engine typically runs in the range of 1000 degrees F to about 1500 degrees F. Please note that this is the temperature of the exhaust gas itself, which does not mean the same thing as the exhaust manifold temperature. The manifold runs somewhat “cooler” due to the airflow under the hood, the engine’s cooling system, and the heat being conducted down the exhaust system. Remember, though, the exhaust gas of a poorly tuned engine may run several hundred degrees higher than optimal at the manifold, which could easily exceed the 1300 degree F operating limit on Jet Hot’s Extreme 1300 coating.
I called Jet Hot and talked with them about their coating options. The Extreme 1300 has the best looking "black" option. It is not glossy, but was described as having a “little” sheen to it and a smooth texture. The Extreme 2000 finish was described as “matte” finish with a texture similar to 80 grit sandpaper. The Extreme 2500 finish was described as “orange peel” but again, more of a matte finish. Jet Hot does offer a “lifetime” warranty with free shipping each way in the first year, so they do stand behind their product. If you are unhappy with your coating, they will re-coat it for you. One of the higher temperature coatings would give more margin in temperature performance, but, then you give up on any gloss of the finish and have a rougher surface finish.
Jet Hot is based in North Carolina, and also has another shop in Oklahoma and is obviously not near me geographically (in Iowa). I am a little leery about having to crate up and ship my manifolds half way across the country and I like to support local vendors when I can. Especially when there are issues and some follow up is required (not that I expected any “issues”). I find that there is an advantage to meeting the people face-to-face, seeing the facility, and viewing the process, and viewing completed parts. This triggers questions to help your understanding that you may not think of on the phone. Also, one can just imagine a horror story of either “damaged in shipment” or “lost by carrier” happening to these difficult to replace cast iron castings.
I have never had much luck with VHT (Very High Temperature) paints on exhaust manifolds. For one thing, they are usually a flat black, and they seldom last very long on the high temperature surfaces. They burn off or flake off, and pretty soon, you are back to the rusty iron. However, I have it on good authority from Rick Horne, fellow PAS Member, that “Rutland” brand high temperature paint, works pretty well. It is made in Charlotte, NC, and is distributed by Ace Hardware. It still has the flat black look like most high temperature paints, but Rick says if the manifold is bead blasted clean, that the Rutland high temperature paint will stay intact for quite a while. He says that it will burn off eventually, BUT, if you just wire brush the bare surfaces, you can simply re-spray it with the Rutland paint and it blends pretty well. With most of the other BBQ (Barbeque, or for Jak in Australia, “Barbie”) or VHT (Very High Temperature) type paints, you pretty much have to start all over again and re-strip the manifold. This is obviously an attractive lower cost option for a project car or a driver where you just want to get the manifold cleaned up, prevent excessive oxidation, and get a uniform color on the iron castings again.
I did some further web searches and found a ceramic coating that had a good balance of the kind of properties that I was looking for. Cerakote has a coating that is good for 2000 degrees F, and it is smooth and a semi-gloss, as opposed to the usual flat black or matte finish high temperature black coatings.
On the Cerakote website, I looked for a "certified" applicator within a 250 mile radius of my home. This led me to Kranz Powder Coating Services, in Columbus, Wisconsin. Jeff Kranz had been factory trained and certified by the Cerakote manufacturer (NIC Industries, Inc.) to apply the family of Cerakote ceramic coatings and is within reasonable driving distance of my home. There are many companies that are certified to apply these coatings across the country, and you can likely find one near your home.
Of particular interest to me was the Cerakote “Glacier Black”. It is their newest black high solids ceramic coating, applied as a liquid and air cured. It is self leveling and very smooth, is deep coal black in color, as well as providing a semi-gloss satin finish that is good to over 2000 degree F. They have other black finishes available, but not with this degree of semi-gloss, deep black color, temperature resistance, and corrosion resistance.
Kranz media blasts the castings, inside and out. Media blasting removes the remaining porcelain and induces compressive residual stresses that are actually beneficial. Jeff also recommended that the inside surface of the exhaust manifold should be coated with Cerakote Insulkote, a white ceramic insulative coating that gets oven cured. The Insulkote is specifically designed for coating the inner walls to provide a reflective and insulating coating that helps prevent the exhaust heat from being soaked up by the manifold casting and allow the heat to be reflected and conducted down the exhaust system. This helps reduce the amount of heat present under the hood which has the added side benefit of helping to combat vapor locking. As mentioned before, exhaust manifold surface temperature is reduced significantly with a reflective coating inside.
As the second operation, the Glacier Black coating is applied as a liquid to the outer surfaces of the manifolds, and then air cured. Oven curing of the Insulkote material has previously driven out any moisture present in the casting. The price is very reasonable, at $250 for the set of manifolds. This seemed to fit my needs, was reasonable in price, and it was within a drivable distance. I could deliver the parts myself, wait about a week, and then go and pick up the menifold without any shipping induced damage to the either the new coating, or the castings.
You notice that I used the term “menifold”. That was not a typographical error. Years ago, my brother, Rick and I, found a set of Pierce-Arrow Model 43 intake and exhaust manifolds at a swap meet. This was before I had acquired the current Model 43 7 Passenger Sedan. We were focused on 1933 Pierce-Arrow parts at the time, and I really was not sure what year and what model Pierce that this manifold set would fit. The seller did not really know what they were for, “maybe for a Studebaker Straight 8?” he had said. But I knew that this was an early Pierce 8 manifold set from looking at other member’s cars. I took the guy’s phone number, took a few pictures, and filed the thought away. A little research revealed that by the casting part number, this was in fact a Model 43 manifold set.
After we were home and thought about buying them anyway, I called the owner and he still had them. He thought it was too heavy and too bulky to easily ship them. The next swap meet that he was going to was the “Hoosier” swap meet at the Indianapolis Motor Speedway in September. We drove down to Indianapolis, wandered the field for hours, eventually found the vendor, and bought the manifold set. It was in fairly good but surface rusted condition. The price was only $40. The trouble was we had to carry it from the infield of the Indy 500 track out to our ancient rusty but trusty Chevy pickup. Do you realize that track is so big that there is a golf course and a road racing course in the middle of it? And, we had no Siberian Husky along, like we previously had at Hershey to pull a parts wagon (See the Cylinder Head Feature Article in the PAS archives for more on the Husky). This is when we coined the term “menifold”, because like many Pierce-Arrow parts, they are built so well with such thick sections, that it takes “2 men” to carry them any significant distance. As we were leaving the field, someone joked "If you didn't have such a big car, you wouldn't have to carry such heavy parts!"
I was reminded of this story again when I went to remove the manifold set and carburetor off of the Model 43 to get it re-coated.
To Remove the Menifold
Removing the manifolds from an early Pierce 8 (updraft Stromberg carburetor) is easy enough. Probably the trickiest part is that you really have to remove the manifolds as a set, including the carburetor, all at the same time. As far as I can see, you cannot easily unbolt the carburetor from the intake manifold while the manifold is still on the engine. The two carburetor nuts that are closest to the engine cannot be removed as you can’t get a socket on them due to the shape of the carburetor body, and there is not enough “swing” room for a wrench to loosen them. Anyway, it is not a good idea to try and leave the carburetor in place because it would not be supported well without the intake manifold. Do not risk damaging the carburetor! The manifold set with the carburetor is a heavy and awkward sub-assembly and is best handled again by two people for removal.
Here are the basic steps and suggestions for a 1931 Model 43 updraft manifold set up. Later downdraft cars are similar, but there are obvious differences. 1929 cars have a different exhaust manifold design than 1930 and 1931 cars. V-12’s are obviously entirely different yet, but some of the same concepts apply.
Once the menifold is removed, find a stable place to work so that you can:
With the help of a friend, we removed the menifold set from the engine. Once on the bench, I removed the carburetor, and then separated the manifolds. I pondered the decision of whether to re-coat both manifolds, or to just coat the exhaust manifold that had already shed so much of its porcelain. The intake manifold, as it does not receive the hot exhaust gases was still quite presentable. My thought was that it would look better under the hood if both manifolds had the same finish, so that was my decision was to re-finish both the exhaust and intake manifold. It turned out that there would be “issues”, and that my mental pondering with the decision was all moot, as both manifolds needed work.
I had taken the manifold set in for media blasting, and in two days, I received a call that the manifolds were back from media blasting to remove the remaining porcelain. It turns out that the porcelain was covering some issues in the castings.
Intake Manifold Troubles
On the intake manifold, two sections of the walls of the intake were found to be paper thin and in fact perforating, resulting in holes in the casting. From the pictures, you can see that the two thin sections are right where the casting has “slots” in it, just above the mounting flanges. The “slots” provide clearance for the “D” shaped clamping plates to allow them to contact more surface area on the flanges. Apparently these sections are cored rather thin anyway. The designer apparently did not want to impede the flow of air/fuel mixture by intruding into the approximately cylindrical intake passage with a boss or irregular shape to provide more wall thickness for the casting. Through usage, corrosion, and media blasting, the casting had perforated, leaving a significantly hole in two intake runners that would have to be fixed.
PAS Members on the Message Board on the PAS website offered a plethora of patch ideas to repair the holes. Since the intake does not see the high temperature exhaust gases, aircraft adhesives, bonded metal patches, JB Weld, and welding were multiple ideas discussed.
There were other problems with the intake manifold, as there were stress cracks radiating from three of the mounting holes where the long threaded studs are mounted. See the pictures for more details.
Exhaust Manifold Troubles
The exhaust manifold had a visible hairline crack in the casting under the heat riser box, between #4 and #5. It did not appear to be structural and there was no sign of leakage, but a crack just the same. There were also stress cracks radiating out from two of the four mounting holes that receive the long threaded studs of the intake manifold. Obviously, some of the adhesive based ideas for fixing the intake would not work on the exhaust manifold, due to the much higher operating temperature.
Solutions for Cracked Manifolds
As many have pointed out or have experienced, there has been a long history of problems with these old manifold castings. Some of the problems were designed in, some are related to the cast iron alloy material used, and some are caused by past owner’s attempts to repair them. These are long fairly intricate castings and are subject to residual tensile stresses from casting, overheating, and thermal cycling. There is also some question about the metallurgy and cleanliness from contaminants and inclusions of the cast iron material used. And, obviously these were made with 1920’s technology.
To solve problems with a cracked cast iron manifold, one can either try to:
Regardless of how you “solve” the cracking issues in the cast iron, you still have to deal with the question of a finish.
The “Menifold” set that we bought in Indianapolis had been “repaired”. An obvious crack in the exhaust manifold which completely separated the #1 cylinder end of the exhaust manifold from the rest of the manifold, had been “repaired” using an arc welder leaving an ugly bumpy scar of a mend. It looks like the menifold continued to be used, the repair was very crude, but somehow held together.
You have probably heard people say that it is “difficult” to weld cast iron. In short, there is no way to successfully arc weld (or braze) two such pieces of cast iron together. At its simplest, the very process of arc welding creates enough heat to melt the filler rod and the parent material at the edges of the part. The melted cast iron and intertwined filler cool and harden and the pieces are “bonded” together. The part seems “whole” again. The trouble is that it creates a Heat Affected Zone (HAZ) on both sides of the weld that has different metallurgical conditions due to the unequal heating and non-uniform heat distribution of the arc welding. The weld joint was very hot, the area next to it, not so much, and the further you get from the weld, the cooler the part. This creates a wide spectrum of physical properties in different areas of the part. This is very significant on cast iron parts. The result….the mended part will easily break in a brittle fracture just either side of the weld due to the different microstructure of the cast iron created by the use of the arc welding process. The part could also easily warp in an arc welding process, also.
Someone who is very talented with an oxy-acetylene torch can pre-heat both sides of the joint area, prior to applying the filler rod and making the weld, but the success of such a joint is extremely dependent on the welder’s skill. Large castings like this are very difficult to pre-heat enough with a torch with anything like uniform heat distribution, as the large thermal mass draws the heat away and gives mediocre weld results.
The best way that I know of to weld large cast iron castings like this is to use the oven fusion cast iron welding method:
Midwest Cylinder Head (cast iron welding)
Midwest Cylinder Head is based in Nevada, Iowa. This is about 100 miles from my home. I knew of them because they had repaired the cast iron cylinder head on this car previously, using the oven fusion cast iron welding technique. The results were wonderful, and once the cylinder head was painted, you could not even see where the weld had been done. See the Tale of 2 Heads Feature Article in the PAS Archive on the website for more details.
I drove the manifold set over to Midwest Cylinder Head and met with them. They had a lot of experience with repairing cracks in cast iron Packard straight 8 manifolds as well as diesel truck manifolds. They were impressed with the design of the Pierce-Arrow manifolds as it had thicker sections and thicker mounting flanges than the old Packard parts. They were very confident that they could fixture the Pierce-Arrow manifolds to minimize any warpage from welding and effectively repair the cracks and holes in my manifolds.
Lead-time was quoted at about 2-3 weeks. It was over the New Year’s holidays, so the lead-time did stretch out to longer than I would have wanted. Typical with many commercial businesses, they sometimes do the “old car stuff” in their non-peak times. Even though it took longer, the quality of the welding, re-surfacing and machining was excellent.
I ordered four gaskets from Olson’s Gaskets. I received the two-piece copper clad manifold gasket set, the carburetor gasket, the exhaust flange gasket between the manifold and the pipe, and the gasket that goes in the heat riser between the two manifolds. The gaskets were well made and the long and narrow manifold gaskets were taped to a piece of 1/4” thick plywood to keep the gaskets from getting bent or damaged in shipping. I was impressed with Olson’s service on delivering the reproduction gaskets.
The gaskets from Olson’s were very good overall, including a nice thick insulating gasket for mounting between the Stromberg and the updraft intake manifold. Also, the gasket for use between the manifolds was a copper clad and armored gasket with insulating material between the cladding layers. This acts as thermal barrier between the manifolds. The only issue that I had was to enlarge one of the four gasket holes that pass over the four long studs that clamp the two manifolds together.
The Manifold's Return
In hindsight, I am glad that I ended up stripping and refinishing both manifolds. I am also glad that I took both manifolds in for welding. Magna-fluxing of both manifolds revealed additional cracks in both manifolds that I had not seen yet. These may have opened up at any time, or could have run for years yet, you just don’t know. But it is best to have all of them repaired, since you have the manifolds off of the car.
When the manifolds came back from welding they were clean and whole and the cracks had been taken care of. The welded areas had been repaired with actual cast iron filler rod. Then the welds had been cleaned and textured with a grinder to camouflage their presence. Invariably, even with fixturing and clamping, the residual stresses in the castings is going to relieve when this kind of heat is applied and warpage will be the result. As the final step in the process, they installed the gasket between the intake and exhaust manifolds, and bolted them together with the four studs that pass through the castings. With everything snugged up, they ran the assembly through a CNC machining center to “deck” the mounting flanges. They only removed a few thousandths of an inch in certain areas, a testimony to the fixturing that was done. This trues everything up and will allow a decent seal on the gaskets when re-mounted.
With the castings all clean, welded, and machined, I took the two manifolds, along with the “tuning port” threaded plug that screws into the elbow of the exhaust manifold to Kranz Powder Coating Services. I had previously talked to Jeff Kranz and he was quite knowledgeable on ceramic coatings. When I talked to him, I had asked the idea of a powder coating to obtain the higher gloss levels, but he was immediately concerned about the long term temperature performance of powder coating (plastic) on an exhaust manifold. He concurred with my selection of Cerakote Glacier Black ceramic as he had previously successfully applied this coating to exhaust manifolds for hot rods and motorcycles with excellent results.
Jeff had his own cleaning protocol and since it had been some time since the manifolds had left the welder, allowing time for humidity to create an oxide layer on the castings, and the fact that they had been “handled” loading and unloading, allowing skin oils to get onto the castings, he would do a light media blasting prior to coating to provide proper “tooth” and surface cleanliness for the coatings to adhere to. The inside surfaces of the exhaust manifold would be coated with the reflective Insulkote ceramic material first, oven cured, then the outside surfaces of both manifolds would be coated with the Glacier Black and then air cured. Make sure to have the flange surfaces, the ones that mate to the manifold gaskets, also coated. You do not want corrosion from non-coated surfaces to seep out and spoil the look that you are trying to achieve.
Again, not wanting to risk damage to either the castings or the newly coated surfaces in shipment, I drove back to Wisconsin to pick up the coated parts. When I picked up the “manifold”, Kranz had processed them just as promised, communicated well through the process, and had done an excellent job with them. Cerakote Glacier Black offers a good looking, semi-gloss, manifold coating solution, at a reasonable cost.
Helpful Ideas for Re-assembly
I could have approached this problem following other roads, but I really wanted to “conserve” the manifolds that came on the car and accepted this as a challenge. I wanted to see if I could once again make these original parts work again. I knew that I had fallback paths if the welding repairs had failed completely. That is one of the best things about the Pierce-Arrow Society.
You may want the full gloss porcelain treatment for your car, or perhaps you want to try the Rutland paint approach. Others will undoubtedly encounter the same kinds of issues that I did, so I wanted to make a case study out of my experience for the benefit of the membership. Repairing and re-coating the manifolds is yet another thread in the tapestry of a Pierce-Arrow owner’s life!