Vast distinctions exist among overhauling, rebuilding, restoring, and blueprinting engines. As a customer, you should know exactly what you are seeking from a machine shop. Communication, clarity, and a clear understanding of terminology are critical to achieving the desired result.
This Tech Tip is From the Full Book, FORD FLATHEAD ENGINES: HOW TO REBUILD & MODIFY. For a comprehensive guide on this entire subject you can visit this link:
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Basically, an overhaul could include deglazing cylinder walls,re-ringing existing pistons, a possible bearing change, and installing new gaskets, just to get the engine running. Rebuilding may include new parts but not necessarily complete machining of cylinder bores or crank grinding; it might require only a polish. Restoration usually includes all new parts and complete machining to factory specs as outlined in the factory manual. Blueprinting includes installing all new premium parts, complete machining to specified tolerances, balancing, and more to achieve optimum performance and durability.
Depending upon where you live, finding a machine shop to tackle your block may or may not be easy. The flathead is not a complicated engine, but it does have its idiosyncrasies, and a shop that typically rebuilds small-block Chevys might not be the place to go. We mean no disrespect, but the shop needs to know flatheads. If it doesn’t, don’t pressure the shop into learning or experimenting on yours. It might be a costly mistake for both parties.
Be sure to take plenty of photographs of your block and any little identifying marks it may have. You don’t want to hand over a fairly good block but receive a different and perhaps poorer-quality block after the work is done. You might even want to put your own mark on the block before handing it over or shipping it out of town.
I heard one story of a guy shipping a complete, brand-new rotating assembly to an engine builder. When the engine came back, however, it soon seized. Tearing it down revealed that the builder had switched out the good internals for a set of not-so-good originals. It pays to be aware of such possibilities.
It’s always smart to do plenty of research before you settle on a machine shop. You can learn a lot about a shop by checking the Internet, where people are quick to air their grievances. You can also ask fellow enthusiasts about their experiences. Caveat emptor (let the buyer beware) is the phrase to keep in mind.
Blueprinting and Balancing
These words hold much mystique, and summon images of a black art. However, they mean nothing more than making sure that parts are balanced and that the engine is assembled to certain specifications and tolerances recommended by the manufacturer for optimum performance for the desired application, such as street use, racing, or touring.
If you are rebuilding a stock engine, it’s fairly easy to follow the Ford specifications found in the various service bulletins. Most people building hot rod engines use components from a variety of sources. Nevertheless, you should still follow specs for main bearing clearances, ring gap clearances, cam timing, head port and chamber volumes, torque for bolts, and so on.
Factory specs are parameters that suffice for mass-production engines (taking into account time, labor, materials, and so on). They meet the driving needs of the general public with a broad range of driving styles. A blueprinted engine meets and exceeds those factory parameters.
Theoretically, there is no tolerance for a blueprinted engine. It either is or it isn’t, and there’s no in-between. If you build two engines to factory specs, there will always be variances between rod and main bearing clearances, variances in piston clearances, deck height differences, valve-spring pressure differences, and intake and exhaust port and chamber volume differences. If you blueprint an engine for racing at Bonneville, for example, there should be no variances. It should be built to a specific race spec.
Properly blueprinting an engine takes many hours, a lot of patience, and a lot of skill. To achieve a properly running, reliable engine, you need to follow procedures and not just throw it all together.
Balancing is also worth worrying about, because a well-balanced engine is like a well-balanced checkbook: Keep it on the good side and life will be good. Theoretically, to do it correctly you should preass emble the engine before balancing the components, so that any subsequent machine process or task does not affect the balancing act. The order of the day is: pre-assemble, machine if necessary, and balance.
If you are running a mixture of aftermarket components (crank, rods, pistons, and so on, all from different suppliers), it is essential to balance the parts. Of course, you can avoid this work if you buy a rotating assembly from one manufacturer. Even if you do, it is still worth checking the parts for quality. I was a crank grinder in my youth, and there were days when I ground good cranks and days when I was in a hurry and just wanted to get it done. Those grinds were within tolerance but were not my best work.
Weight matching and dynamic balancing are the two steps to balancing an engine.
To weight match, you weigh the pistons and the rods individually on a balancing scale to determine the lightest of each. Then, remove a little metal from each, until all of the pistons weigh the same as the lightest piston and all of the rods weigh the same as the lightest rod. Parts are usually measured within .25 gram.
A balancing fulcrum is also used to determine how heavy a rod is at either end. If a rod is a little heavier on the big end (the main bearing end), a little weight is removed from that end to balance the rod. (The procedure employed at H&H is outlined in this chapter.)
Dynamic balancing is the process of balancing the rotating assembly, including crank, rods, and pistons. Although the crank itself is put in the balancer, bob weights are installed to replicate the rod and piston assemblies. Be sure to record all of the weights for the rods, pistons, and associated components; they will be needed later when you balance the crank.
Almost no factory production engine comes precision balanced. Even some so-called performance engines aren’t balanced to within 1 gram, as are the engines balanced by H&H on its Hines electronic balancer.
Does balancing make any difference? The answer is yes. According to Mike, “A well-balanced flathead makes for a smooth-running car. It produces efficient power by eliminating power-robbing vibration and imbalance.” A flathead is balanced internally, as opposed to a 454 Chevy, a 400 Chevy small-block, and 460 Ford trucks, which are balanced externally; each uses a harmonic balancer.
Balancing and Honing the Rods
Although the rods produced by companies such as Scat are extremely well balanced, Mike likes to double-check them because balancing flathead internals is important to a smooth-running engine. In addition, Mike suggests that if you’re reusing stock rods, you should definitely resize the big ends, because years of wear will have forced them out of round. Moreover, you should definitely balance them, because Ford’s tolerances were more liberal. Ford service bulletins give an acceptable weight of 451 to 455 grams; with a little care, all of the rods can weight exactly the same.
Assuming that your desire is a smooth-running, long-lasting engine, then taking your time and being careful will be rewarded. Precisely honing both rods is paramount.
You can balance connecting rods at home, and with a little care, you can match them exactly. You will enjoy a feeling of satisfaction for a job well done.
If you’re reusing original rods, you need to put the big ends back to round, because they will have stretched through the years. Each rod cap is put in this Sunnen rod and cap grinder, in which the mating surfaces are ground flat.
You can clearly see the freshly ground rod cap faces. Obviously, because the surfaces have been ground, when the two rod halves are assembled, the hole will be out of round.
Next, the assembled rod is set in this Sunnen AN 300 dial bore gauge, which measures the size of the big end. The gauge indicates how much the hole needs to be bored to return it to exact size and roundness.
As two rods sit side by side on the crank journal, the rod pairs are honed together. All of the rods must be at the same factory/bearing manufacturer spec.
The small ends have also become misshapen over the engine’s life, so they too need to be honed back to spec, either factory or that of the piston/pin manufacturer.
A fixture on the ohaus Adventurer-Pro scale allows Mike to weigh the big end of each rod. The rod is balanced at the small end while the big end is weighed.
The Scat box says that the average weight of the big end is 410 grams. On Mike’s scale, the ﬁ rst rod out of the box weighed 409.1. That’s within 1 gram, so it’s okay. The Scat rods weigh 40 grams less than stock Ford rods.
A couple of rods were at the far end of tolerance, so they were lightly ground on the ridge of the rod cap. I’m talking tenths of a gram here; not much.
After all the big ends were matched, each rod was weighed individually to make sure they all weighed the same. Matching them exactly is a bit of a balancing act, but care and patience will get you there.
Material was removed from the crown of the small end of any rods that needed it. Again, it’s a very small amount. If you are doing this at home, measure twice and grind once.
Balancing the Pistons
As with the rods, most modern pistons are well balanced, but Mike likes to be doubly sure. The process of balancing the pistons is much the same as balancing the rods. Ford’s allowable tolerance was 8 grams for pistons with rings and pins.
The pistons, in this case from Egge Machine, were weighed individually. They came in at approximately 403.3 grams each. Cast-alloy Ford pistons typically weighed anywhere from 408.8 to 416.8 grams.
The pins each weighed 93.2 grams. Sometimes you ﬁ nd a rogue pin that doesn’t match the others. They should all match for a well-balanced engine.
Even the clips were weighed (1.8 grams per pair), because the aggregate weight of all the piston and rod assemblies is needed when it comes time to balance the crankshaft later in the balancing process.
After the lightest piston was found, all of the others were lightened to match it; a small amount of material was removed from the skirt just inside the piston bore. This can be a tiresome process.
Balancing the Crank
Typically, if you’ve purchased a new crank from a company such as Scat, you needn’t worry about balancing, but Mike likes to check new cranks anyway. H&H has an expensive, digitally controlled Hines balancing machine.
For the balancing process, the crank is put into the machine, where it rests on V-blocks. The dial gauge to the left indicates that the crank is running true.
Bob weights replicate the aggregate weight of the rods, pins, rings, and clips, ascertained earlier. Mike can adjust the weight by using weights in the box at the top of this photo.
The weights of the various components (rods, pistons, pins, locks, and rings) are entered into the computer (upper right corner). The computer calculates the size of the bob weights needed to replicate the piston and rod assemblies.
The bob weights, which look like giant clamps, are positioned very carefully on the crank to replicate the position of the rods. A laser aligns the crank vertically, and a level is used to locate the bobweight correctly.
Every step of the balancing act is an exacting process. Each bobweight must be positioned carefully to exactly replicate the crankshaft as it would be complete with all eight pistons and rods.
When all the bob weights are correctly installed, the computer calculates all of the information necessary to balance the crank. In this case, as seen in the lower left, a 1/2-inch bit is needed to drill to a depth of 2 inches.
After Mike inputs all of the component weights (pistons, wrist pin, rings, pin clips, and rod bearings as well as the oil allowance, rotating and reciprocal weights, cast-iron or forged crank, and drill bit diameter), the computer tells Mike exactly where and how deep to drill.
The computer display tells Mike exactly when the crank is balanced. This is not a task for the uninitiated. Even though a computer provides the information, it takes a great deal of experience and care to get it right.
Unless you’re a competent machinist and have access to a good shop, it’s best to entrust crack repair to experts. This procedure requires an understanding of castings, core shift, wall thickness, radial curves and intersects, transitions, and interlocking compatibility. You must also follow machining procedures for valve-seat installation and cylinder sleeve installation. A keen eye and an understanding of parting lines and core shift are imperative, so you are not fooled by what does and does not constitute a crack.
Magnaflux inspection almost always reveals a crack (or three or more) in a flathead block. Here, a 1-inch crack is inside the port directly under the valve-seat.
A long punch struck with a brass-headed hammer marks the place where Mike will drill. Use care with this operation when working in tight conﬁ nes and at odd angles.
Using a small handheld electric drill, Mike drills through the port wall, being careful not to drill too far or to allow the drill chuck to make contact with the block.
Take care when tapping the hole, because you’re working with cast iron, in a conﬁ ned space, at an angle. You don’t want to break the tap.
A tapered Sea lace plug is used to pin the crack. You can probably tackle this at home, but take care not to make matters worse. Flatheads can be full of cracks, so seek expert advice about reparability.
Mike uses tapered Sea lace plugs from Silver Seal Products in Trenton, Michigan. You don’t want to have to buy a box of 100 to repair your block.
The thread of the screw is coated in Seal-Lock Fluid Weld from Cylinder Head Supply and then screwed into the block using a socket and extension. You feel it tighten as the taper is screwed home.
The head of the screw is ground off using a carbide burr and an air tool (in this case) or an electric drill. Some force is needed, but take care not to damage the port.
A carbide burr tool grinds away the remainder of the screw, leaving it flush with the port wall. Wear goggles or glasses when performing these operations, because the chips fly.
A follow-up Magnafluxing operation clearly reveals the screw in position. Obviously, you’ve sealed a big crack by making a smaller one, which creates the need to pressure seal the block after the stitching process.
Here, you can clearly see the second screw in the stitching process. Pressure testing reveals porosity that Magnafluxing does not detect. Likewise, ceramic pressure sealing helps ﬁll these tiny ﬁssures.
Unless you have found the holy grail in the form of an NOS block or you are going French, your engine needs a rebore. Whether you need sleeves or not will depend upon the previous bore job, rust, cracks, and other defects.
A machine shop uses a boring bar to machine the cylinder to the next oversize while maintaining correct geometry in relation to the main bearing bore. This is essentially blueprinting. H&H uses a Kwik-Way FN boring bar, and all blocks are set in the boring table located on the main bearing registers, which allows all bores to be square to the main bearing axis. H&H also has a Rottler boring table and bar with a precision preset mounting fixture for V-8 blocks, as well as a Kwik-Way FW boring bar for the 13⁄4- to 31⁄2-inch cylinder bores of the V-8-60s.
Some shops also use a boring plate that applies torque to simulate the head being torqued. This induces stress in the block, which results in even more accurate bores. This is only really necessary for race engines, however. In Mike’s opinion, the plate should be used when honing the block and not when boring the block. Not using the plate during honing negates the work you did during boring.
The boring bar makes two passes in each cylinder: The first is rough cut with a brazed carbide insert tool, followed by a finish cut of .010 inch with a full carbide tool to achieve the best possible finish. This step minimizes any subsurface fracturing and aids in the final honing to achieve the desired finish for ring seating and sealing.
The boring, honing, and finishing of a block must be performed with the pistons and rings you intend to use. Measure the piston diameter, check the manufacturer’s suggested clearance tolerance, and machine accordingly.
The block is carefully positioned in the boring machine and made level. This shows the leveling fore and aft, but you need to check left to right also.
The boring bar is carefully aligned with the hole to be bored. The bar has three centering pins that simultaneously and uniformly expand to center the boring bar in the cylinder bores.
A boring bar micrometer is used to set up the cutting tool to the exact size.
The boring bar is run up and down the bore at slow speed to ensure a round and straight bore from top to bottom. Using the auto stop rod and plunger on this Kwik-Way FN boring bar, Mike always sets the stop point to keep the tool from exiting the bottom of the bore.
In the case of a very high performance build, you might want to have the block align bored. This operation re-creates a straight and round bearing bore while maintaining proper cam-to-gear dimensions.
H&H uses the Kwik Way LBM align-boring system, which was used around the world by early Ford engine remanufacturers for Model As, Bs, V-8s, and others. Kwik-Way supplied specific aligning fixtures for specific engines.
Mike assembles his Kwik-Way FN line-boring ﬁ xture. All blocks are located on main bearing registers, which allows all bores to be squared to the main bearing axis.
A cutting tool (the round pin with the pie-shaped slice taken out of it) is inserted into the boring bar and locked in place with a setscrew on the underside.
A “stab” micrometer slides over the tool and is used to measure the tool’s precise height. You are unlikely to have this micrometer in your toolbox.
The main caps, in this case H&H billet steel caps, are torqued down, after which the hole is bored. The process is repeated for each of the three mains, resulting in perfect mains alignment.
If your block has cracked cylinder walls, severe water damage, or porous pinholes (rot from inside the water jacket through to the bore), it is necessary to sleeve that particular cylinder. A trusted machine shop can handle the work and supply the sleeves.
Before you begin, evaluate all eight cylinder bores to determine the final bore of the non-sleeved cylinders. That way you can select the correct sleeve to match the other bores while leaving proper wall thickness (at finished bore of the other cylinders) for the sleeve.
Sleeves for general automotive use, such as those from Melling, are cast iron (basically the same material as the block) to ensure proper heat transfer and durability/wear characteristics. Specialty sleeves for high-performance and race engines that require harder ductile iron are available from Los Angeles Sleeve Company.
Sleeves on all flathead blocks at H&H are stepped at the bottom and installed in the block with a .002 inch interference fit. As a general automotive rule, final cylinder wall thickness on each side should be approximately .090 inch. As mentioned above, final bore size of the block dictates the correct sleeve dimensions. Attention to detail is very important and failure to do so can be costly.
When sleeving, Mike bores all blocks with a 1/4-inch-thick step register shoulder on the very bottom of the cylinder bore. The sleeve sits on this step permanently and prevents sleeve slippage during the engine’s life.
Step sleeving is critical on V-8 flatheads because these blocks are a full water block from top to bottom. Moreover, due to the inconsistent casting procedures of the 1940s and 1950s, adding a step at the bottom of the bore absolutely ensures that the sleeve does not slip down or move from side to side.
Procedurally, sleeving a block is the same as boring, except that the final operation is done with a 90-degree tool bit to stop the step flat
for sleeve registration. The process of boring the sleeve after installation is the same as the cylinder-boring operation described above.
Sleeves are available for all bore sizes, from 31⁄16 to 33⁄8 inches.
Here you can clearly see the step at the bottom of the left-hand bore on which the new sleeve seats. The second cylinder is good and does not require sleeving.
A small amount of two-part J-B Weld is mixed and spread around the step. It’s a ﬁ nicky process that is no more easily done from the top or from the bottom. Do whatever is most comfortable for you.
Here you can see the J-B Weld spread around the step. Take care to accomplish an even spread. Standing the block on end might make it easier.
The sleeve is positioned in the bore. The bottom outside edge of the sleeve is chamfered to ease insertion into the bore. Careful alignment is important.
A thick block of aluminum and a heavy dead-blow hammer are used to drive the sleeve into the bore. It’s hard work, but if everything is machined correctly, the sleeve hammers home precisely.
The sleeve is hammered all the way home to butt against the step. The excess J-B Weld is wiped away.
The power hone removes the very last few thousandths of material by finely grinding the bore to give a precise tolerance between the piston rings and the cylinder wall. H&H employs a Kansas Instrument/Peterson hone, accompanied by a Sunnen dial bore gauge.
With the intake manifold bolt holes securing the hoist chain, the block is carefully lifted up into the honing machine and set on the bed. Flathead blocks are heavy, and care is needed when moving them.
Mike cleans out the head stud threads with a clearing tap. A little cutting oil or even WD-40 helps with this process.
After the threads are cleaned and the head studs are installed, Mike installs the billet aluminum torque plate, which is bolted down. The nuts are torqued to 55 ft-lbs
A Sunnen dial bore gauge is set on a calibrated Sunnen setting ﬁ xture and is used to measure the cylinder bore so that it can be honed to the ﬁ nal speciﬁ cation. The manufacturer of the pistons determines the bore size, regardless of whether they are forged or cast and the engine’s application is normally aspirated or blown.
With plenty of Sunnen honing oil, Mike makes multiple passes: at the bottom of the bore, at the top, and in the middle. He uses Sunnen AN stones to rough hone the bore to within .001 of ﬁ nal size. He then uses Sunnen AN ﬁ ne stones to ﬁ nish the bore and achieve the proper cross-hatch for ring sealing. The ﬁ nal hone results in a round and straight ﬁ nished cylinder wall.
The bore is checked constantly with a Sunnen dial gauge until it is right. This is an exacting process that takes some experience to master. After eight holes, you’ll likely have it down.
The ﬁrst bore is now nicely honed to size. It needs to match the proposed piston and desired clearance perfectly.
Decking or resurfacing the block is a mandatory and important step. It ensures that the block mating surfaces are flat, smooth, and parallel to the mains and crankshaft; it also results in proper head gasket seal. After 70-plus years, a flathead block can be extremely twisted, and checking it with a straight edge is not accurate enough.
Again, the block is registered on the main saddles for the resurfacing operation, which provides a deck surface parallel to the main bearings. The block effectively squared and side-to side equal deck heights are established, registered off the main bearings.
H&H uses a Storm Vulcan segmented stone surface grinder with a continual coolant flow on the work surface to prevent burnishing and excessive heat during the operation, ensuring a distortion-free finish. Similar to a Blanchard grinder, the Storm Vulcan uses a fixed stone headstock to parallel-grind material with an infinitely controlled hydraulic table, allowing for any degree of surface finish. It can surface anything up to V-12 Lincolns. H&H surfaces not only the deck but also the intake manifold deck.
The block is put up into the machine and made level fore and aft. Because the block rests on the mains, it should be level left to right, but it’s always worth double-checking.
Grinding wheels become dull or glazed with use, and their cutting surfaces need to be constantly dressed (cleaned). This sharpening tool is used to dress the grinding wheel.
The grinding head moves backward and forward across the block automatically while coolant keeps the block cool. After each pass, the head is lowered a few thou sands of an inch.
The deck surface is now clean of imperfections. Some corroded flatheads need a few passes to get a ﬁ nish this nice. This was an old relieved block.
Cutting a power slot in the block, now referred to as “relieving,” is an old performance technique that is rarely employed these days. Mike says that approximately 10 percent of old blocks are relieved. Unfortunately, a power slot decreases compression and therefore is a trick reserved these days for blown engines. A power slot does not work with Ardun heads.
The process involves machining a channel between the valve ports and the cylinder bore. This process facilitates the flow of the fuel charge into the cylinder. The slot is usually between 1/8- and 3/16-inch deep and should be nearly as wide as the bore.
Pressure sealing is a critical step in a flathead rebuild. It helps seal any missed cracks, captures any loose particles that may have escaped the thorough cleaning process, and helps ensure that any crack repairs on the block are sealed. The process is necessary because cast iron is porous. The ceramic sealer circulates throughout the cooling system and permeates the internal casting to reduce buildup of scale and to permanently impregnate any hidden casting fissures. The process is time-consuming but ensures superior block integrity.
The equipment looks similar to that used for pressure testing: One plate bolts to the deck, and another blocks off the water pump. After all machining repairs are completed, the block is cleaned thoroughly before the head plate and the water pump plates are attached.
Ceramic sealer is preheated to 180 degrees F before being pumped into the block for 30 minutes. The system is then back-pressured and drained completely before the procedure is repeated on the other side of the block. The block is then set aside to air catalyze for 24 hours.
Valve-seats are made of hardened material capable of withstanding extreme heat. They used to be cast iron but are now primarily chromemoly, Stellite, or beryllium.
Mike installs new hardened valve-seats on all of his engines for a number of reasons, including historic accuracy and because of today’s fuel formulations. Over the years, H&H has disassembled engines with all, a few, or sometimes no valve-seats.Valve-seats are important because they transfer heat from the valve and facilitate cooler engine operation and good valve-to-seat sealing.
To complicate matters, Ford valve-seats were set at two depths from the top of the deck. The driver-side valve-seat was even with the deck, and the passenger-side valve-seat was counter-bored from the block deck. Seat replacement brings the seat back to its original height (correcting sunken-in and wide-ground seats), allows for establishment of proper seat width, and prevents valve-seat recession due to today’s fuels.
A commonly overlooked but mandatory step in block analysis and preparation is the removal of existing valve-seats. This step allows for Magnafluxing under the seat, where most cracks originate and travel down the ports and/or block top.
After the hardened valve-seats are
The block is set in the mill to be perfectly level in both planes. Two levels are used simultaneously to facilitate this process, which involves time and patience.
The cutting tool is set to cut the relief for the new seats. Notice the previously cut seats in the foreground. Mike insists on installing new seats in every block he ships.
The guide that registers on the hole for the valveguide is slipped into the block. You’re unlikely to have this tool on the shelf, but a crafty person can make one.
With the guide in place, the machined seat surface is given a coat of red Loctite; you don’t want those seats coming loose later because of different expansion rates as the engine heats up.
The seat is positioned on the guide, and a steel drift is placed on top of it. You might be able to make these tools at home.
A well-used steel drift is placed over the guide, which is hammered home. Remember that every block has 16 seats.
Use a flashlight to determine if the seat is ﬁ rmly seated. Because of the interference ﬁ t, it takes some hammering to install seats properly. You can do it without a guide, but this is not recommended.
installed and the initial three-angle seat profile is completed with profiling tools, Mike finish-grinds the seat to the final three-angle configuration using a Sioux grinder and stones. The stones are at 60 degrees for the interior of the bowl of the seat, 30 degrees for the top of the seat, and 45 degrees for the actual valve contact area.
Stones are available in various grits, from course roughing to finish. In this operation, Mike has already profiled the seats with a profiling carbide and now fine-finish dresses the seats and checks the contact area on the valve.
Typical valve grinding equipment includes the three grinding tools: 30-degree, 45-degree, and 60-degree, and the guide (right). This is the same guide used to install the valve-seats.
Mike carefully dresses (cleans) the grinding wheels, or stones, using this handy ﬁ xture. He moves the adjustable cutter in his left hand up and down the surface of the wheel.
Coat the seats with marking blue, often called Dykem after a popular brand. The marking blue is cut away to reveal the shiny ground area.
In what is known as a three-angle valve job, Mike begins with a 30-degree cut on the uppermost side of the valve-seat. The 30-degree cut is followed by a 60-degree cut.
The upper 30-degree and lower 60-degree cuts have a very slim line between them. This is where the 45-degree cut is made. The exercise should achieve a perfectly sealed valve job.
The ﬁnal 45-degree cut should be minimal. This is a crucial cut that actually seals, so take care not to lean too heavily and overcut.
The 45-degree cut is even and provides a perfect seal with the valve to maintain all-important combustion pressure. As with most engine-building tasks, cutting valveseats takes time and patience.
All 16 valves are then hand-lapped in. Hand-lapping will give you a slightly wider sealing surface and therefore a better valve-to-seat seal.
Permanent marker on the 45-degree cut shows how the valve is seating. Mark each valve to correspond with its seat so that they go back in the right holes during assembly.
If you purchased a complete stocker with the original heads, chances are those heads will go on your trophy shelf or hold the garage door open (unless you are using them in a restoration project). The engine may have old aftermarket heads that might be serviceable. However, they could cost more to restore than a new set of heads. Of course, the choice is yours.
It’s advisable to buy NOS heads rather than trying to restore original heads, as Mike is doing here for a customer. After all the welding, the various holes still have to be machined and ﬁ nished. You have to ask yourself if it is it worth it.
For those going the restoration route, original iron heads are the way to go. This pair has been blasted, Magnafluxed, and inspected for cracks. None were found and they’re good to go.
Surfacing the Heads
Most flathead engines are at least 60 years old. They’re not ready to be pensioned off yet but are getting there. Nevertheless, we keep rebuilding them. Original or cool old aftermarket heads will no doubt have warped over the years and need professional resurfacing.
The heads are put up in the Storm Vulcan for surfacing. Unlike the block, which was registered by means of the mains saddles, the heads have to be carefully leveled both left to right (shown) and fore and aft.
For the inexperienced, the multiple, minute adjustments can be tedious, time-consuming, and frustrating. But for an experienced rebuilder such as Mike, this is a fairly straightforward operation.
After the wheel is dressed, the head is surfaced until it’s flat. As heads tend to twist over the years, it can be tricky to make the head flat while removing the minimum amount of material.
Written by Greg Kolasa and Posted with Permission of CarTechBooks