Flathead Myths courtesy of Tony Baron
Flathead History Lesson courtesy of Charlie Clark

Although a great leap forward when it was originally introduced in 1932, by the ’50s the aging motor could not stand up to the new generation of overhead-valve powerplants like the small-block Chevy. At around the same time, old-time hot rods gave way to modern musclecars and street machines. Then, about 20 years ago, traditional street rods suddenly became cool again. At first everyone was dumping modern engines into old metal, but eventually the supply of stock bodies dried up and reproduction glass bodies took over. The new engines overpowered the old chassis, so modern suspensions and disc-brake swaps were added to the mix. Eventually you could build a whole street rod out of aftermarket commodity parts. The downside was, as Flathead Engineering’s Charlie Clark puts it, street rods “began to look about as exciting as a belly-button-everyone had one.”

Among this herd of sheep, a few original hot rods were brought out of retirement, complete with gennie flatheads as the powerplant. Dressed with up to four carbs and that unique flathead sound accentuated by glasspacks, the old codgers were suddenly the rage again. It was a statement, in effect saying, “I am not a cookie-cutter rod.”

The new old cars got a lot of attention. Guys who once dreamed of owning a flattie back in the ’50s but who had neither the time nor the money were now in their 50s, with lots of disposable income. Younger guys yearned for a simpler, back to basics approach. Flatheads began to come back, and prices of swap-meet stuff skyrocketed. This encouraged the old-time flathead parts guys (or their sons) to start repopping the old parts. Like all fads, once started, the process fed itself.

Now it’s 2005, and the flathead’s resurgence shows no sign of diminishing. In fact, the growing flathead movement has basically sorted itself out into three distinct groups. At one end there are restorers who insist on putting everything back to exact original condition. Most in this group will accept a modified flathead as long as it is period-correct, with no obvious modern technology visible. At the other extreme are dry-lakes, Bonneville, and nostalgia drag racers who have applied modern technology to the point where in some instances it is questionable whether the engine still remains a true flathead: Once-85hp engines now produce over 400 hp on gas and have exceeded 700 hp on fuel-all this on an engine with only three main bearings.

The pinnacle of flathead tech, this Dick Landy-built 700-plus-horsepower motor powered Ron

Somewhere in the middle is the largest group: Potential street rodders who just want reasonably fast hot rods without having a cookie-cutter, 1-800-car. For this group-whether building a rat rod, yanking a Chevy that just doesn’t look right in that old Deuce, or building a brand-new car-the outlook couldn’t be rosier, even better than the flathead’s heyday … so long as the bucks hold out. You can now build a brand-new flathead. There are builders on the left and right coasts and all points in-between who assemble reliable, powerful, 150-200hp engines, or you can buy new parts and build one yourself. A good supply of new French (really) blocks exist and outfits like Scat make new H-beam rods and sell cranks with up to a 4.5-inch stroke. Ross, Wiseco, Egge, Arias, and others make pistons in any configuration you desire. The old cam grinders-including Isky, Schneider, Elgin, and others-have both old and new cam grinds. New stainless valves are available from several sources. Baron, Edelbrock, Sharp (Wilcap), Navarro, and Offenhauser make both old-style heads as well as improved new configurations.

Still not enough? There are kits to install Weiand and Magnuson superchargers, or even one or two GMC 71-series blowers. Fabled Stromberg 97 carbs are back, but you can also upgrade to modern Holley four-barrels or even electronic-fuel-injection systems. Finally, there are brand-new aluminum blocks and Ardun OHV conversion heads and valvetrains. On the following pages, we’ll take a look at some of the stuff available for the flathead and also cover the lineage, interchangeability, and secrets of this proud forebear of modern hot rodding.

EVOLUTION

The ’38-’48 59A block (right) has an integral cast-in bellhousing. The ’49-’53 8BA block (

From its debut in 1932 to the end of its U.S. production life in 1953, the flathead Ford underwent three major evolutionary changes. The first-design ’32 through early ’38 engines had only 21 cylinder-head studs and until mid 1936 even used poured babbit main bearings. Reserve these early blocks for collector cars due to their inferior head-retention and bearing design; speed equipment availability for them is also severely limited.

Starting in July 1938, the blocks went to 24 head-retention studs. These second-design ’38 1/2-’48 blocks (often referred to as “59A” castings) retained an integral cast-in bellhousing, used a distributor that mounts flush to the front cover with a horizontal shaft on the front of the engine and had insert-style main bearings but still used full-floating rod bearings (one bearing shell for each rod pair).

The third-design “8BA” ’49-’53 engines have a bolt-on bellhousing, the distributor was moved to the top-right of the engine, and modern insert-style bearings are used on both the mains and rods. After 1953, flathead production continued in other countries, most notably in Europe, where the engine continued to be used in French military vehicles through the ’90s. French blocks have some unique features and are covered separately.

As we go to press, word is just in that Mark Kirby at Motor City Flathead has joined forces with Shadow Rods to develop an all-new, improved ’49-’53-style aftermarket cast-iron flathead block. This block is completely beefed up, with four-bolt caps, reinforced bottom-end and webbing, furnace-brazed sleeves (max bore is 3.5 inches), and new-design head studs that tie into the bottom of the block. It will use a new oil pan and special bolt-on universal bellhousing that accepts most modern transmissions. Stay tuned for further updates on this project.

ROTATING ASSEMBLY

The flathead blocks to get are those with a 3 3/16-inch bore. These include the ’39-’53 Mercury and ’46-’53 Ford castings. Although it sounds weird in this modern age of thin-wall castings, the 3 3/16-inch-bore, U.S.-built flatties can be bored 0.125-inch (1/8-inch-over). In fact, unless you have a badly core-shifted block, most of them can accept a whopping 0.1875-inch overbore (3/16-inch over standard). Earlier 3 1/16-inch-bore blocks will only go 0.090-over.

In the old days the hot ticket was dropping a ’49-’53 Mercury 4-inch-stroke crank in place of the Ford 3.75-inch-stroke unit. Speed-O-Motive still advertises Merc crank cores if you want to go this route, but it’s no longer necessary, what with all the aftermarket alternatives available. Scat offers affordable cast Pro Stock cranks through 4.375-inch stroke, with either 2.00- or 2.138-inch rod journals. Custom billets stretch all the way to 4.5-inch stroke. The 2-inch rod journals are very popular because their diameter and width permits the use of readily available 215-inch-style Buick/Olds/Rover V-8 bearings.

DAMPERS

Most stock flatheads never came with an effective harmonic damper. But with modern solid cams and big stroker cranks, overall engine rpm and piston speed is considerably higher than the old stockers. Flathead gurus like Don Ferguson and Tony Baron strongly urge that hot rod engines run a harmonic damper. One solution is adopting a small-block Chevy damper. The Chevy’s crank diameter is only 0.060-inch smaller than the flathead’s. With such a small difference; it’s relatively easy to take a little off the Ford snout then slightly hone the inside of a Chevy balancer so it slips over the Ford crank.

FRENCH BLOCKS

Original 50-plus-year-old blocks without cracks are getting scarce. Although new aftermarket iron blocks are reputedly under development, right now a real-world solution to finding a good core for your flathead is to start with a brand-new French block. For reasons known only to the crazy French, flatheads were used in French Army trucks through the early ’90s. Mullins, a leading purveyor of surplus Jeep and other vintage military parts in Texas, accidentally discovered a warehouse full of brand-new French blocks about to be junked during a European trip searching for Jeep stuff. He bought the entire French stock, and at last count still has at least 500 blocks, 120 complete engines, and over 2,000 rods.

French blocks are about 30 pounds heavier than a standard flathead, which is a good indication of better metal and thicker walls. Reputedly, they are cast with 10 percent higher nickel content, and the quality of the modern castings is a lot smoother with much less core shift. Tony Baron says French blocks can be bored 0.250-over (1/4 inch). With a 4.5-inch-stroke aftermarket crank, that yields 334 cubic inches.

However, there are some significant differences in French blocks compared to the originals. French blocks are hybrids, essentially a ’49-’53 8BA in terms of deck height and front-end, but with the integral cast bellhousing and corresponding oil pan as found on the ’38 1/2-’48 59A. Two things to watch out for are an extra water hole in the block and the lack of a breather standpipe in the block. There is also an ugly governor mounting boss on the left-rear of the block that many rodders prefer to machine off.

Because the French version was used in trucks, the intake- and exhaust-port throats are choked down under the valve pockets, so extensive port-work is required for racing. However, the main caps are beefier than traditional stock flatheads. Unfortunately, old-school resistance to this “new and improved” part is so extensive that the SCTA has banned the blocks from competing in classic land speed racing classes. Apparently, the old boys’ network doesn’t want any youngbloods crashing their exclusive country club. But that just leaves these pristine virgin blocks for us normal street guys.

COMBUSTION CHAMBER

Normally we’d title this section “Cylinder Heads,” but on a flathead, the heads-having neither ports nor valves-only form the combustion-chamber roof. The mixture must follow a tortuous U-turn path out the block-mounted intake valve, over to the main part of the chamber above the piston, and then back out the exhaust valve. This lateral flow severely restricts flathead breathing capability, although it does promote what today’s high-tech engineers term swirl and tumble, which enhances fuel mixing and combustion.

Making power with a flathead is a fine balancing act, juggling the higher thermodynamic potential of raising compression against improving airflow through the combustion chamber. Traditional flathead airflow management practices call for relieving the block-removing metal between the valve-seat sides closest to the cylinder bore. This improves airflow, but the resultant effective combustion-chamber-volume increase lowers the compression ratio, in turn decreasing horsepower and fuel economy. Trying to gain back compression ratio by using popup pistons may improve airflow provided proper attention is paid to the transfer area and overall piston-to-combustion chamber interface. The best balance has been the subject of debate for over 60 years.

Currently the most popular approach is running a big popup piston, but with a scallop on the side adjacent to the valves to keep the transfer area clear between the valves and the cylinder bore. Recommended bottom-line street-gas-friendly compression ratios are between 7.5-8:1 on naturally aspirated engines and 6.5-7.0:1 with a blower. As for cylinder heads, Baron, Edelbrock, Navarro, Offenhauser, and Sharp (now sold by Wilcap) all have their adherents.

Reliefs between the valves and bores are much less pronounced than the old days, only about 0.080-inch deep instead of the old-school 31/416 inch. Research has shown there’s relatively little air movement over the base of the block. Instead, air wants to go over the front of the valve and hit the chamber roof. Most hot rod engines use oversize valves. Small-block Chevy valves remain popular, but with reduced-base-circle cams they may be too short to permit proper lash adjustment. Correct-length flathead 1.800 intake/1.600 exhaust valves are available from flathead specialists like Baron Racing.

Seal the heads to the block using slick new graphite-impregnated head gaskets available from Best Gasket, Red’s Headers, and Tatom. Copper head gaskets are sold by SCE. Fel-Pro and Victor continue to make head gaskets too.

EXOTIC CONVERSIONS

Ferguson’s Ardun kit includes heads; valvetrain spark-plug tubes; valve covers; Coke-bottl

Compared to the original Ardun (bottom), the new kit (top) includes stronger rocker stands

In 1947, long before Zora Arkus-Duntov became famous for his work developing the Corvette and performance Chevrolet parts, he and his brother Yura designed what has been considered the ultimate flathead performance mod-turning the engine into an overhead-valve hemi. The company they formed to produce these heads was named “Ardun,” an acronym derived from their last name. Only 200 original sets are known to exist, but fortunately, Ardun heads and associated conversion parts are back, reproduced in improved form by Don Ferguson of Ardun Enterprises. The present-day Arduns are CNC-machined using high-grade 356-T6 aluminum, have refined combustion chambers, and improved oiling and valvetrain components. They fit original ’39-’53 blocks, French blocks, and (perhaps the ultimate evolution) Ferguson’s new aluminum block. Relieved blocks must have the reliefs filled to use Ardun heads.

CAM AND VALVETRAIN

With no rocker arms, a flathead’s total lift must be generated entirely by the cam lobe. According to Baron Racing, the limiting factor is not piston-to-head interference, nor even valvespring coil-bind-it is running out of cam bearing clearance for the lobes. Short of machining the block oversize for custom roller-cam bearings, even with a reduced base circle this limits max cam lift to about 0.460 inch. Tony Baron says that a good-running flathead should have no less than 0.400 lift and about 250 degrees duration at 0.050-inch tappet lift. Schneider’s 278F solid (0.420 lift, 250 degrees at 0.050 duration, 110-degree lobe separation angle) is one grind that falls within these specs. Many hard-core guys still swear by Isky’s 400-JR solid (0.400 lift, 244-degrees at 0.050, 111-degree LSA).

One flathead builder, Dave Tatom, offers a unique line of custom grinds with wide 114-degree LSA for naturally aspirated engines, and 116-118 LSAs for blown motors. Tatom believes spreading the centers helps combat overlap-induced reversion with the flathead’s siamesed center exhaust ports. The 270-F, Tatom’s best all-around cam, is said to work well on normally aspirated or blown, stick, or automatic cars, with good idle quality and 18-19 inches of vacuum. Ground with a 114-degree LSA and 112-degree intake centerline, it has 0.395-inch lift and 234 degrees duration at 0.050. Cams like this with good aftermarket heads are capable of producing 200 hp and 240 lb-ft naturally aspirated, and over 300 hp and 350 lb-ft with a blower.

OILING

The stock flathead oiling system is marginal for performance use. Most builders convert the stock oil system to a full-flow design with a modern, remote-mounted oil filter. There are several techniques; the accompanying photos show the method preferred by Baron Racing. At present, the only aftermarket custom oil pan available is from Ardun Engineering. Most flattie builders modify factory pans. Melling still makes a high-volume oil pump (PN M-15). A truck oil pickup tube assembly (PN 8RT-6615) is required to use the M-15 as well as the standard volume Melling M-19 in ’48-and-earlier engines; ’49-and-up engines can use the stock pickup.

TRADITIONAL INDUCTION

It was only at the very end of the flathead’s reign that the first small four-barrel carbs appeared; back then everyone used multiple-carb setups. Strombergs were the favorites, but Chandler-Grove/Holley, Zenith, and Rochester two-barrels were also in use. Stromberg in England is producing new Strombergs again. Improved internal components and casting technology make them more reliable and leak-free.

The Thickstun two-carb high-rise intake (today marketed by Baron) is an excellent street setup and it even provides clearance for the stock generator. Baron also offers a modern version of the famous Tattersfield/Baron four-carb race intake in more civilized street form. The current incarnation is 3 inches taller than the originals and has smaller 1 1/2-inch ports (vintage versions had 1 3/4 ports, but the new casting is thick enough to hog ’em out). Tom Roberts’ new two-piece crossflow utilizes the latest in airflow technology. Different top-halves are available for mounting a variety of induction setups. Edelbrock, Wilcap (Sharp), and Offenhauser continue to market a wide variety of intakes.

EFI

Yes, you can have a classic flathead with modern fuel injection. Hilborn and Ardun Enterprises offer EFI conversions that look like old-time stacks but with EFI nozzles. TBI injection through billet Stromberg 97 carb-like throttle-bodies is available from Flathead Engineering. Mooneyes also offers throttle-bodies that resemble Strombergs. A new player is Gemini Electronic Fuel Injection, a complete bolt-on flathead conversion kit based on the self-programming Prodigious fuel injection system. There is also an Australian outfit, Flatattack Engineering, offering plenum-style, TPI-like systems controlled by either GM Delco or MoTeC computers.

SUPERCHARGING

Tom Roberts makes this trick two-piece intake. The high-tech engineered design has a runne

A unique feature of Magnuson’s Eaton blower is the bypass valve (arrow) that opens under c

Flatheads may not have the cubes or brute airflow potential of many of today’s modern mills, but there is a solution: Bolt on a supercharger. The flathead’s compression ratio is well suited to supercharging, and besides, what could be more hot rod than a blower poking through the hood? Magnuson offers an Eaton blower kit, while Joe Abbin of Roadrunner Engineering has Weiand 142 and 174 supercharger setups.

COOLING

The improved ’49-’53 pump (left) can be used in place of the early pump (right) by pluggin

Typical water pumps, from left: a ’38-’48 passenger-car pump modified for a bolt-on pulley

Coolant needs to remain in liquid form when it circulates through the motor. Back in the old days, all cars used low-pressure cooling systems, so coolant often boiled. If it boils, steam pockets form, and when you have steam, you’ll get cracks. The solution is to raise the boiling point by upping coolant-system pressure to 17-21 pounds, using a modern crossflow radiator and higher-pressure cap. A high-pressure system will run fine with no boiling, even at 190-210-degree gauge temps.

Not all flathead water pumps are created equal, though. For improved cooling efficiency, original ’49-’53 pumps have more impeller vanes than earlier models. Speedway Motors offers pumps with sealed bearings that do an even better job in both early and late configurations. Tom Roberts starts with the Speedway pump, modifies it for even more flow, and also redoes the snout to accept modern, bolt-on, serpentine-belt pulleys. Ultimately, you can move up to one of Cornhusker Engineering’s custom front cover and late-model water-pump setups.

This is MSD’s 8BA billet flathead distributor (PN 8574) that works with all the trick MSD

IGNITION

The ’39-’48 flatheads used a direct camshaft-driven front-mount distributor; ’49-’53 engines use a gear-driven, vertical-mount distributor on the right-front of the engine. Early and late distributor styles can be interchanged by using the corresponding front engine covers and cam drive. While exact ignition timing will vary per combination, in general flatheads running gasoline like about 23 degrees total advance normally aspirated and just 19 degrees with a blower. No one runs the old weak stock ignitions anymore. Traditionalists can go with Vertex or Mallory mags, while modern guys may want to move up to MSD or Mallory electronic distributors. Some fuel-injection setups even run distributorless coil-ignition setups. Of course, this modern stuff requires a 12-volt electrical system. An alternative are Pertronix conversion kits that fit inside the original distributor; they retain the classic look, and versions are even offered that function on 6-volt power.

EXHAUST

A wide variety of headers are available for flathead engines, which certainly should not retain the restrictive stock exhaust manifolds. As its name implies, Red’s Headers is the place to go for the widest selection of street-style headers. Also check out Speedway Engineering’s offerings. Ultimately, there are equal-length race headers available from Tatom Custom Engines. Some builders also recommend installing exhaust-port dividers to split the siamesed center exhaust ports.

TRANS ADAPTERS

With modern flatheads routinely putting out 250-300 lb-ft of torque, the original trannies obviously aren’t up to the job. Fortunately, a wide variety of adapters are available to mate the venerable motor to today’s automatic and manual transmissions. The king of adapters is undoubtedly Wilcap. It offers adapter kits to mate GM automatic transmissions and Ford C4 automatics to ’49-’53 8BA blocks, as well as a variety of adapters to mate both early and late flatheads to most GM and Ford manual transmissions. Wilcap also sells ’32-’48 Ford mechanical-clutch hardware.

Flat-O Products sells well-designed, complete kits to install the Ford C4 automatic and T5 manual behind either 8BA or 59A engines. Provided you have an original bellhousing, you can use available Trans-Dapt adapters to install Ford passenger-car transmissions from the mid ’60s to the late ’70s behind the ’49-’53 flatties. Centerforce offers clutches and flywheels.