Pierce-Arrow Society Feature Article
A Tale of Two Heads
Cylinder Heads, That Is
by Chris Diekman
The old cylinder head on my 1931 Pierce-Arrow didn't look that bad. It was painted gloss black with a good engine paint. It kind of bothered me, though. Every time I would raise the hood, there would be a small pool, the size of a quarter, of coolant residue on the surface of the head between cylinder 4 and cylinder 5. I would drive up and park at a car show; I just knew that in addition to dusting off the body, I had to clean the cylinder head off. It just looked like a crack in the paint on the flat broad top surface of the head. It didn't leak that much. It wasn't like coolant was spraying out all over the place. It was just seeping out, and it was annoying. I decided that a compression test was in order.
It is hard to find a compression tester that will work with a cylinder head with such large 7/8" spark plug holes as the early Pierce-Arrow eights have. Many modern compression gauges have a tapered rubber plug to seal on the edge of the plug hole in the cylinder head, however, they are meant for a spark plug hole that is about 1/2 the diameter of our plugs.
The Solution: Find yourself an old Champion Commercial or C4 plug that is the correct size to thread into the Pierce-Arrow head. It seems like almost every swap meet has a rusty bucket of spark plugs that you can sift through. The beauty of these old plugs is how they were assembled. A hex nut collar retains the porcelain core in the steel threaded base of the spark plug. If you remove the smaller upper hex nut, the porcelain center section with upper electrode can be removed from the metal base. Use the metal base as an adapter for your compression gauge. Thread the base into the spark plug hole that you want to test. Insert the rubber tapered end of the compression tester into the hole in the base of the old spark plug. You now have surfaces that the rubber on the compression tester end can seal against. If you can't find one of these old plugs, a machinist could easily turn out an adapter collar for you on a lathe.
Hold the gauge and firmly press the tapered rubber against the spark plug base while someone helping you cranks the engine. The large pistons will definitely try to push the end of the gauge up out of the adapter! Usually about 4 or 5 compression strokes will give the maximum reading. Run your compression tests with the engine warmed up to operating temperature, but all the spark plugs removed. If you try to do a compression test on a cold engine, the readings won't be as high or accurate, especially if you have aluminum pistons that haven't yet expanded to operating size with the heat. The key with compression testing is consistency. An engine in good condition will have all cylinders reading within a few PSI of each other. What is it supposed to read? A quick rule of thumb is to take atmospheric pressure at 14 PSI x Compression Ratio. On an early eight, the compression ratio is about 5:1. 5 X 14 = 70 PSI is the target reading. If the head has been planed off in previous repairs, you might find higher compression readings due to the effective reduction in size of the combustion chambers. On the other hand, if you find lower compression, you need to look for the cause. Worn rings? Valve sealing? Bad head gasket? Or, in my case, a crack in the cylinder head. Seven of my cylinders measured right at 70 PSI, but one cylinder, #5, read only 50. It is a sinking feeling. This was more than annoying. Once I knew that I had a compression leak, in addition to the coolant leak, I knew...something had to be done.
Two Heads Are Better Than One
The old Pierce-Arrow cylinder head did not look that bad, even though it was painted John Deere green, it wasn't the Pierce-Arrow olive green that you occasionally see on the early eights. The head was kind of rusty, and leaning up against a crudely made wooden saw horse style table. It was Hershey, years ago, in a year when the swap meet fields were on grass. It was more than damp, and we didn't have to worry about the dust, because it was mud.
"How much for the old flat head?" I inquired, pointing casually to the old green casting.
"That's for a Boo-ick", the seller stated authoritatively.
"OK, how much for the Buick head?" we asked again.
"It's a straight-eight", the seller stated very matter of factly. He was right about that, eight big spark plug holes. As you know, Pierce-Arrow heads are not like some Packard heads where they cast "PACKARD" in large letters along the length of the head. It makes identification pretty simple if the name of the manufacturer of the car is cast in place in 1" tall letters! I know a Pierce-Arrow straight-eight head when I see one. It just seemed like a bad time to bring this up and try to correct him on what brand of head this was as the critical Hershey Negotiation Ritual was about to begin, and we didn't want the price to suddenly go up.
"Fifty" the seller said sternly, strategically leaving out the commonly used word "dollars". Maybe he was in a bad mood because of the rain and the mud. In any case, I was glad it wasn't "Two-Fifty"!
"How about Forty?" we bravely offered, matching his custom of omitting the word "dollars".
"Forty Five" was the seller's quick comeback, again saving several words for another day.
"Done", and with that, the traditional Hershey negotiation dance was over. I never did tell the seller that his "Boo-ick" head was really for a Pierce-Arrow. He was happy, we were happy, we left well enough alone. He was probably tired of hauling it around.
Then we had the daunting task of hauling this 58 pound piece of cast iron from the Chocolate Field back to the truck, as there was no way we were going to carry this thing around in a backpack for the rest of the day!
For several years, my faithful Siberian Husky had traveled to Hershey with us. We had bought parts and borrowed various red coaster wagons to carry the parts back to the truck. It was then that it occurred to us that "Tundra" the Husky, who just loved to pull, could actually help us in pulling the wagon of parts back to the truck. So many fellow car enthusiasts saw the rare sight of a happy and proud sled dog contentedly pulling a coaster wagon load of Pierce-Arrow parts across the field and through the parking lot. Tundra enjoyed the attention and the cheers, and we enjoyed the help! That was a happy memory.
The "Hershey" Head was a #2 type head with the large 7/8" spark plug holes, just what I needed for the 1931. It was a good thing that my brother and I bought this many Hershey's ago, I knew it would be useful some day! I had a spare head!
I could see that there were some deep pits in the John Deere green paint job. The combustion chambers were carboned up, but at least they were not rusty. The water passages though, were no longer elliptical and symmetrical. They were hour glass shaped, elongated, and eroded. This poor engine must have sat without the benefit of rust inhibitors for a long time. I could see a faint image where the elliptical cutouts in the head gasket were to allow coolant to pass between the head and the block, and the corrosion actually made some of the holes in the head erratically larger than the holes in the gasket! I don't know if this thing will even seal! At least it doesn't look cracked. But as I would find out, looks can be deceiving.
The first step in the head restoration was to cryogenically treat the old casting. My brother, Rick, did the treatment at Controlled Thermal Processing, in Illinois. Cryogenic treatment stabilizes the microstructure in the casting and is an excellent preparation for subsequent welding and machining operations.
I knew that welding cast iron was difficult to do well in normal circumstances. Now I needed someone to do it on a somewhat rare cast iron cylinder head. The casting needs to be pre-heated, the heat maintained during the welding process, then cooled slowly once the welding is done. The heating MUST be done in a controlled process because variation in temperature leads to warpage and cracking due to thermal stresses. Waving a torch over the surface may work for pre-heating small parts, but not for large castings like this head.
I called a local machine shop and they offered that "they have a welder in the corner and they might be able to do it". Not very confidence inspiring. I needed to keep looking. Just running a weld bead across a crack in an iron casting does not work. It may look good, but it creates a Heat Affected Zone right next to the weld and will often crack right next to the weld bead. The choice of filler materials is also critical. It is best to find someone with a lot of experience in welding cast iron. This is no place for experimentation and part time welders.
A friend and neighbor who is a retired machinist, who has made some parts for our cars over the years, talked to some other hobbyists and came back with a referral for a welding shop. The steam tractor hobby is alive and well here in Iowa and involves a lot of repair of rare iron castings. "Midwest Cylinder Head" was the recommendation based on wonderful work done on irreplaceable antique tractor castings.
Midwest Cylinder Head is located in Nevada, a small town in rural Iowa. I had a mental image of a small shop on a back alley, dimly lit, and littered with rusty and broken Chevy V8 and hot rod blocks. Boy was I wrong!
A phone interview revealed that this was a large shop that specialized in fleet repair of cast iron truck heads, blocks, and manifolds, as well as tractor engines, racing engines, and antique car and antique tractor casting repair. They had welded many Ford flatheads and some Packard flat heads. What intrigued me the most was their Team approach in assessing the head, testing it, cleaning it, welding it, re-testing it, and texturing it to hide the repair.
A tour of the facility revealed a clean and modern commercial building in an industrial complex. There were many projects in process, large Caterpillar diesel engine blocks, Ford pickup fleet engines, John Deere diesel engine heads, and a 50's Chrysler Hemi block with the side blown out due to water freezing in the water jacket.
Twenty-six people worked together to take the old Pierce-Arrow head through all the processes. First it was sandblasted clean and shot peened, completely removing the ghastly green paint. A thorough magnafluxing revealed a small crack in the #1 spark plug recess. Funny, I didn't see a crack, but with the iron powder in place and the powerful magnafluxing magnet switched on, there it was. My spare head needed to be welded to repair the crack. This was a pivotal step and revealed a fault that the eyes could not see. They further determined that they could repair the eroded the water passages. The actual crack was ground with a hand grinder to form a "V" to lay the fillet of the weld in.
Once clean and magnafluxed, the Pierce-Arrow head was bolted to a large Caterpillar diesel head to serve as a fixture to prevent warpage and distortion. The whole assembly was placed in a large oven and heated cherry red to 1500 degrees F. The repair area was welded using cast iron rod (not nickel) that is very similar to the original casting material. The eroded water passages were deck welded with the cast iron sticks and built up again. All the welding was done working through small access hatches in the gas fired oven. Once the welding was done, the whole Pierce-Arrow/Caterpillar head assembly was allowed to cool down slowly in the oven.
The next day, once it was cool, the welded head was removed from the fixture and had an initial pressure test. All holes were plugged and 40 PSI of air pressure was applied through one hole while a soap mixture was applied to all surfaces of the head. Bubbles will quickly show any leakage.
If the test is good, the machining of the welded areas is completed and the head is machined flat to enable a good seal to the block. Once the machining is done, a second pressure test is done. If all is good, the repair areas on the cast surface are textured by skilled artisans using hand operated electric grinders to simulate the as-cast texture. Finally, a rust preventative spray is applied and the head was packed for transport.
The work was excellent, and once painted, you cannot tell where the welding was done. The water passages which were all corroded and elongated had been welded shut and then machined back to the original size and shape and were now in wonderful alignment with the holes in the gasket. All the erosion and wash out areas had been restored.
With the green paint gone, I noticed that the outer surface of the head had some pretty noticeable pits from corrosion over the years. I thought about welding and machining back these cosmetic issues, too, but I really wanted to preserve the sand cast texture of the head. I did not want the billet smooth look on this old eight cylinder or to have small areas on the top and sides of the head that had obviously been machined. There were so many small pits in several areas, welding did not seem like the answer.
What I found useful was Devcon 10110 Plastic Steel Putty. This is a Part A/Part B steel filled epoxy that is machinable and paintable. This material hardens nicely and will hold the "as cast" texture and will easily camouflage large corrosion pits. Devcon also makes a #300 Cleaner which is recommended to clean the surfaces and lightly etch the area to be repaired for an enhanced bond by providing some "tooth" for the epoxy to adhere to.
I used a solvent and a brush to remove the rust preventative from the head in the areas that I wanted to apply the Steel Epoxy, leaving the rest still protected from rust. I then used the Devcon #300 Cleaner as instructed on the label. Once dry, I mixed small batches of the Steel Epoxy. A popsicle stick works well for mixing and applying the material. I just used my fingers then to smooth out the material and press it into place on the affected areas of the head. I then pushed pieces of cotton cloth into the semi-hardened Steel Epoxy to simulate the texture of the casting. You have to experiment with different cloth samples to get the right weave to give the Steel Epoxy the right look.
Once the epoxy dried, I selectively sanded the repair areas with 100 grit emery paper to get rid of any excess epoxy and do the final shaping on the repair areas. Mainly, I just wanted to fill the deep rust pits and some gouges in the head and eliminate an observer's first impression that "boy, this head must have been in bad shape". Don't get the idea that I coated the entire surface of the head with this stuff. I probably only applied the Steel Epoxy to three or four total square inches of the head. Again, I was not trying to make a billet-like glass smooth head. It is a sand casting, after all. Applying the material to a large area like body putty over a large dent in a fender may result in cracking or de-lamination with heat cycling and time. I just targeted 1/8" or larger rust pits that were now evident after the paint layers had been removed and the head had been cleaned.
After several days, I cleaned the entire head with solvent and a scrub brush. You need to be very careful here because in a humid environment, the whole head can "flash oxidize" and almost literally turn orange before your eyes. You need to be careful in minimizing the handling of the head once it is clean. I had the head strategically positioned on the picnic table, outdoors, with several layers of plastic sheeting underneath it. You also have to protect the now machined mating surface from scratches and abrasive surfaces.
Once the solvent had evaporated and I had wiped off the head with clean cotton cloths, I painted the outer surface of the head with Bill Hirsch black engine enamel. I did one light coat, and after it dried, I did a second coat. This is nice paint; it covers well, and has a nice black gloss appearance.
I let the paint cure for a week, and then made preparations to change the head on the car. I took a bunch of before pictures and video tape of the engine and all the linkages to answer questions that would inevitably emerge later during re-assembly. Taking video has the added benefit of including your narrative of observations and verbal notes to yourself.
Don't lose your head!
To remove the old cylinder head on a Pierce-Arrow eight (minor variations for different years):
You gotta be kidding! Remember, this thing weighs 58 pounds! It may be useful to remove the hood to get better access to the head. We simply worked with the driver's side hood up. It is up to you. The head is so heavy, and is hard to reach at the centerline of the car. It is very difficult for one or even two people to manhandle it out from under the hood and it is hard to get more than two people working under the hood. You are leaning way over the fender with a heavy item; it is not good for your back. We used an engine hoist, telescoped way out to pass over the fender and reach the head. But, you ask, how do you get the head out? How do you get a hold of it to connect it to the hoist?
Remember the spark plug base from the old Champion C4 plug? If you have two of them, you can run a 3/8" hex bolt, about 3" long, up through the bottom of the C4 plug base (just cut the bottom electrode of the plug base off first). A couple of fender washers and a hex nut on the top side will retain the bolt in the spark plug base. One of these can be threaded into the spark plug hole in cylinder 3, and a second one can be threaded in the spark plug hole in cylinder 6. The up-turned bolts now provide a place to fasten both ends of a short length of chain, thus forming a "handle", like on a suitcase. I used 500 pound test chain from a hardware store with links large enough to pass the 3/8" bolts through, and secured the end links to the bolts with fender washers and nuts. With the "handle" in place, the hook of the engine hoist can be brought in and hooked to the chain handle. You need to keep the length of the chain to a minimum with no slack as you will find that you don't have much clearance for the hoist if the hood and radiator brace rods are still in place. You can't waste what little clearance room that you have by just taking up the slack in the "handle" chain. Your lift will be up against the bottom of the hood and the head will not have moved yet if you have too much slack in the chain handle. If your head is aluminum, or your head uses the smaller 14 mm plugs, you may want to consider using 4 plug bases in 4 spark plug holes to better distribute the load and not risk damaging threads in your spark plug holes.
The head was not "stuck" or bonded to the block, so the engine hoist easily lifted the head from the block on the first attempt. But, this is a two person job. My wife, Delphine, operated the hydraulic cylinder on the hoist, while I guided the head out from under the hood without banging it into anything. As you know, the end of the head is already right up against the firewall, so it is necessary to "guide" the now elevated head. Get a rag or cardboard in between the head and the firewall. Once the head is up and clear of everything, the hoist can simply be wheeled back away from the car.
I had obtained a new head gasket from Olson's Gaskets. They were friendly, efficient, and prompt. Best of all, the new head gasket was in stock and soon arrived in a box supported by a piece of 1/4" thick plywood, minimizing the chance that it would be bent, folded, twisted, or damaged in shipping.
I painted both sides of the new gasket with Permatex Copper Spray-A-Gasket. This is an aerosol product with flakes of copper suspended in it. The copper flakes fill minor imperfections and provide a better seal. The product is not a "glue", but when it dries, there is a slight "tack" to it, sort of like the feel of a "post it" note, that is helpful in keeping the gasket in the right position while you are working. I applied three light spray coats to both sides of the gasket, using a simple bent up coat hanger to hang the gasket up to dry.
I cleaned off the top of the block with solvent to remove dirt and residue. Once the gasket is dry, place it on top of the block, aligning the water passage holes in the gasket with the holes in the top of the block and the large cylinder holes in the gasket with bores in the block. Look twice to make sure that the gasket it right side up and aligned properly. It sounds silly, but people have done it wrong and then wonder what went wrong. It's not like it is easy to look later.
Install the spark plug bases and chain handle on the "new" head on cylinders #3 and #6. Lift the head with the engine hoist, get it balanced and level on the hoist, and wheel it toward the car. Again, two people working together is best as it takes some maneuvering and coordination to get the head into the proper position without hitting the head against anything, damaging either the head or whatever you banged into.
Once the head is hovering above the block, I used two steel rods, just a little smaller in diameter than the head bolts as "guides" or "drifts" to align the head, gasket, and block. On opposite corners of the head, insert the rods through the head, the hole in the gasket, and into the hole in the block. With the steel rods in place, you can lower the head down and they will help keep everything in alignment and help keep the gasket from shifting. Once the head is down on the block, visually check the alignment and overhang on all 4 sides (look under the other side of the hood and compare the gasket position and look for uniform alignment of the head with the block. Adjust as needed. If it is really off, you may have to lift the head again with the engine hoist. Once you are satisfied with the alignment, remove the engine hoist and remove the two spark plug bases and chain "handle".
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It is not so much thread lock, but thread sealant that is needed for the head bolts. Loctite makes a variety of thread sealants. If you do not apply sealant or apply enough sealant to your threads, coolant will wick up through the threads and leak out onto the head. Apply the sealant to the bolts and start them in all 28 locations. To tighten them, follow the tightening order in the head bolt torque pattern from PASB 95-2. I use a torque wrench and work up to the specified head bolt torque of 60-65 Ft-Lbs in three steps. I set the torque wrench for 20 Ft-Lbs and go through the torque sequence completely. The pattern starts in the middle of the head and then works outward in a clockwise pattern. Then I set the wrench for 40 Ft-Lbs, and go through the torquing sequence a second time. Then I set the wrench for 60 Ft-Lbs, and go through the sequence for a third time. This is all done on a cold engine (you just put the head back on and it hasn't run in a while). The head bolts will need to be re-torqued after the engine has been run for a while and everything has settled into place. But always torque your head bolts on a cold engine. This reduces the risk of stripping out the block.
Go through the torque pattern three times. It doesn't take that long; don't get in a hurry, now. Remember, you just paid to have this cast iron head machined flat; you don't want to warp it again. Remember, torquing and re-torquing of the head bolts should always be done on a cold engine to avoid stripping out the threads in the block.
Re-install the distributor, paying particular attention to NOT moving the distributor shaft. It should drop right back into place if nothing has been disturbed. If the shaft has been moved, or the engine has been turned over for some reason, the relationship between the distributor drive and the distributor shaft will have to be re-established or the timing may be off. The distributor drive interface is a rib going into a slot. It can only fit a maximum of two ways. You can easily confirm the relationship by checking piston position of one of the cylinders against the rotor position inside the distributor. Re-install the other items in the reverse of their removal.
If your horn is mounted under the hood, make sure it has a good clean ground when you re-mount it. I used a little emery paper to remove some of the new paint from the mating surfaces on the head and the horn mount bracket and a little dielectric grease from the car parts store to keep the bare metal from corroding and compromising the connection.
Again be very careful in re-installing the sensor bulb for the water temperature gauge. I used a very narrow strip of Teflon tape to insure a good seal between the pipe threads of the bulb and the head. If you trim the width of the tape down to about 1/4" wide, you won't see any of the white Teflon tape once the fitting has been tightened into the side of the head. First install the outer fitting. Then, use two wrenches again, one to hold the outer fitting, and one to tighten the inner collar, and watch the fine sensor tube closely for signs of binding, twisting, or kinking.
I cut my own water outlet gasket from grey paper gasket stock from the auto parts store. I just used the casting and traced around it, cut it out with scissors and a razor knife. I used a slight film of black RTV type gasket sealer on the water outlet side to retain the gasket. Just a film, not a bead! I specifically did not want excess sealant squishing out, and I specifically did not want to seal the other side of the gasket to the head.
As preparation for AACA showing, I installed a set of NOS Champion C4 plugs that Tundra (the husky), Rick, and I had found in a plastic bucket at a local swap meet. AACA requires black finished spark plugs, or it is one point per plug penalty! Once everything was back together, I refilled the system with coolant and watched for leaks. The engine fired on about the third run of the starter. It ran smoothly, possibly helped by eliminating the problem of the low compression on cylinder #5.
For several weeks to follow, I enjoyed the unmistakable smell of fresh paint curing under the heat of the engine. It kind of reminds you what it must have been like many years ago, a magical time when these cars were new.