The Ford flathead V8 is one of the most familiar engines of the automotive world, but there are a few lesser-known features that are worth a closer look.
Introduced on March 31, 1932 and produced in the USA all the way through 1953, the Ford flathead V8 must be one of the most well-known engines across the automotive world. After all, the beloved flathead powered millions of Ford vehicles and helped to launch the sport of hot rodding. Among car enthusiasts, there’s a veritable mountain of flathead V8 lore, but the engine has a few unusual and interesting features that don’t often come up in the conversation.
Many Ford and Mercury V8s produced between 1938 and 1948 came straight from the factory with sleeves installed in all eight cylinder bores (above). The purpose of these dry, thinwall liners (wall thickness .041 inches) was to eliminate the need for expensive boring and honing equipment when the engine was overhauled. A mechanic could simply pop out the sleeves (a light press fit) and install new ones along with the replacement pistons and/or rings. The concept was not unlike the replaceable wet liners in modern diesel engines. On the Ford V8, hot rodders could discard the sleeves (“tin cans,” they called them) and fit .083-inch oversized pistons in the bores, increasing the displacement from (for example) 221 to 233 cubic inches.
Unlike most any other American V8, the flathead was equipped with not one but two water pumps, one in each cylinder head (red arrows above). Henry Ford himself originally called for the V8 to use no water pump and rely upon thermo-siphon coolinig like his Model T, but that proved to be inadequate and the small twin pumps were added on the way to the 1932 introduction. In 1937 the pumps were relocated from the heads to the block, but cooling remained a trouble spot for the flathead V8 throughout its life.
The unusual-looking ignition unit (yellow arrow) was driven straight from the front of the camshaft, with a distributor cap on each side and the coil mounted directly on top of the cast-aluminum housing. Inside were dual breaker points to increase coil saturation and an adjustable vacuum advance mechanism. Reportedly, Mallory Electric founder Marion Mallory had a hand in the development
Mechanics didn’t much care for the setup as it was located deep in the engine compartment, buried behind the radiator, and difficult to get to. For its part, Ford intended for the distributor to be removed and serviced on the bench with special tools. In Blue Oval lore, the ’32-’41 unit shown above is called a “helmet” distributor. From ’42 through ’48, the crab-style distributor with a single cap was in production, and for ’49-’53 a conventional timing cover and distributor were adopted.
On a flathead V8, the crankshaft is not centered in the crankcase. Instead, the crank is offset in the block more than a quarter-inch in the direction of rotation. The purpose of this gimmick, sometimes known as désaxé (French for unbalanced) is mainly to reduce thrust against the cylinder wall on the power stroke. Ford used .265 inches of offset in the 1935-42 V8s (see above) and a smaller amount on the V8-60 (see our feature on the smallest flathead V8 here.) While the approach was somewhat novel in the flathead’s era, it was known in the early days of the industry and it’s commonplace on all kinds of automotive engines today.
For most of its production life, the flathead V8 was equipped with cast-iron cylinder heads, but from 1933 through mid-1937, cast aluminum heads were installed at the factory (some produced by the Bohn Aluminum & Brass Corporation of Detroit). The performance of the light-alloy heads was perfectly fine—indeed, aftermarket racing heads for the flathead were almost invariably aluminum—but there was a problem, and the Ford V8 became somewhat infamous for it.
Over time, the heads, studs, and block, all dissimilar metals, would become bonded together via electrolysis, making the heads nearly impossible to remove. Mechanics developed a thousand different tricks for breaking them loose, none of them ideal, and in the auto repair industry, this was possibly the flathead V8’s least favorite quality Trucks in this period continired to use cast-iron heads, while Ford’s service replacement parts were iron as well.
By no means are these all the odd or difficult features of the flathead V8—for example, the lack of any factory mechanism to adjust valve clearance, or the exhaust ports routed through the cooling jackets. Maybe you’ve discovered some unusual aspects to the Ford V8 yourself. If so, feel free to share them with us in the comments section below.
I heard that the sleeves were more of a wartime production to cut down on engine block finishing. Instead of a Ford and a Mercury line Ford just ran the Mercury line with the larger bore and installed sleeves to put the bores down to 3 1/6 for Ford applications. Something about the DOD not wanting anything larger than 221 CID. I could be wrong…
According to our information, the liners began sometime in 1938 and were used by both Ford and Mercury. However, we are always looking for more and better info.
I’ve come across engines with sleeves which only needed a ring job but I was told that if you knock the liners out the stock Mercury pistons fit. Of course I cannot verify that as I haven’t done it–yet. It would be nice to find out…
It’s a good, informative article but you should mention why cooling the flathead was troublesome. It has almost 4 feet of exhaust manifold going through the block that has to be cooled. The side exhaust outlets are a neat feature, but they cost a lot of cooling capacity.
Thank you, we appreciate your interest. The purpose of this story was to explore items that aren’t covered in every other flathead V8 article.
I have rebuilt quite a few flatties, most with a push for performance. Of course the problem is heat, but it’s easy to overcome. With 2 water pumps the coolant isn’t in the radiator long enough to cool down. Remove the pumps, cut every OTHER blade, drill a 1/4″ hole in the rest, and add restrictions in the thermostat housings.
This tip came from Smokey Yunick, and from experience, it works very well.
I heard that before. One old Ford guy told me to always run thermostats. I did that and even though my flatties favored the upper half of the gauge I seldom had a boil over…
If that idea came from Smokey then NASCAR probably outlawed it the next day.
I’ve heard that the port diameters and cam was different for each cylinder bank. One bank was optimized for low end power, one for higher RPM power.
Was the higher displacement Mercury engine the same block as the 239.5 cod Ford?
And there was a special corner reserved in Hell for the guy that decided to put one of the water pump mounting bolts inside the pump itself from 1937 on.
LOL you are probably right !
I have a 19 block with dry sleeves. When I worked for a Ford dealer they had cutter like a hole saw that was used to run down the head studs to help free the heads. When the head on the bolt inside the water pump became corroded away I found if you drove a 1/4 inch whitworth socket on to it you would get enough grip to undo the bolt, that if it did not brake ….
Used to work in Automotive with an old Ford man’ he said they were bad about blowing coolant out. Fitting washers in the outlets calmed the problem.
I heard the same thing
You could start the engine with one head removed ,interesting to see how fast those pistons move
I see that engine somewhere with one head removed that was slick I have a 53 I guess the top distributor it’s on a pop loader it runs the hydraulics
Never has been a sweeter sounding engine, with dual exhaust and a pair of Smitty’s
My flathead in a ‘42 Ford truck had the fastest response to throttle opening of anything I’ve ever owned. With the fuel pump stop the engine it could be prone to vapor lock.
The unique sound is a function of the firing order, which is a little unusual for a Detroit V8. It is the same as the recent Ford Coyote V8, which actually sounds remarkably similar to the flathead when equipped with similar mufflers. Definitely not the deep rumble of a Windsor, FE or 385-series engine.
Thanks for a great read!
Readers, any thoughts on what’s happening in the “engine room” picture? Looks like the line has a series of run-in motors, but their elevation seems wrong to couple to the engines.
Appears to be “go, no-go” lamps above each station, and, as many stations again in the adjacent room!
In the photo, the engines are being mechanically “broken in”, so to speak. Each one is temporarily connected to a direct-current electric motor which spins the engine (I assume at various speeds set by the operator). Note that the engines lack carburetors, ignition wiring, exhaust connections, or coolant connections, so this is not a setup involving running the engine against a dynamometer, although the drive motor current gives some indication of the amount of internal engine friction. While being motored, the engine lube system would be filled and functional. Perhaps the engines were run either for a fixed time period or until the motor current dropped to a predetermined level.
Can’t confirm this but I was under the impression that the exhaust was routed through the block to minimize warm-up time.
I must be a minority, those Ford sidevalves were a lemons from before release. Sidevalve may have been just ok on the A but by the early 30s and with all the issues they had to make engines that even ran made them ancient. Especially the exhaust through the block. Really what was Henry thinking!OHV technology was tried and proven, even if they only made a 6. Though Henry had the volume to make an OHV viable. One that does not boil and crack!
Even 20 years later the Y Block was out of date before it was released. And that dopey exhaust around the front of the head,, masterfull design,,NOT.
GM had OHV V8s in Caddys Pontiacs and 55 in Chevs.And Mopar had hemis,, though prehistoric flat head 6s. The Y block an engine that should have been made before the war. Then it would have been excellent.
As for thermocycle cooling,, Ts fry because of it,, and Ford 8&10s do also. Not hard to fit a waterpump to those then they do not get hot
In the late 20’s and early 30’s when this engine was designed, there was little if any advantage to OHV in a passenger car. The main advantages of OHV are ability to have higher compression ratios and better breathing at higher RPM. the poor fuel available limited compression, and poor materials and the quest for smooth torque at low speeds limited RPM. Chevrolets of the period are OHV but don’t have a performance advantage.
And, in fact, OHV engines had a huge drawback. The overhead moving parts required a significant quantity of lube oil, which drained back to the sump over the relatively hot cylinder head surfaces. That caused rapid sludging (oxidation) of the relatively additive-free oils available at the time.
“L” or flathead engines hot surfaces exposed to the oil were limited mostly to the undersides of the pistons and these engijnes had relatively fewer oil passages subject to sludge plugging.
Even in the 1950s, few owners of OHV automotive engines went to the expense of using Series III heavy duty motor oils to prolong engine life.
My high school ’51 Merc had vapor lock problems. I tried the potato on the pump, carried cold water in a bottle, wooden clothesline pins, how frustrating. Remember those tricks? Then one day I discovered a loose nut on my ignition switch. Added a lock washer and tightened the nut and solved the problem.
There should be more articles like this most people today don’t even know what a flat motor is I love it thank you for the great read I would love to forward this to one of my friends
Allan in Laguna Niguel.
Having cracked a ’53 mercury block deck surface due to overheating, I was fascinated by the cadillac flathead V8, which runs the exhaust port back out the “v” between the cylinder banks, and out the top of the engine. I could not find any fault in any of the three y-blocks I owned (rather than throwing a rod).
I bought a ’51 Merc with a seized engine. When we pulled it apart we were stunned to find the rod it had thrown had snapped the cam shaft into three pieces. The guy who sold it to me said it happened ar highway speeds.
I had a ’50 Mercury, bought from a friend who installed aluminum heads and intake manifold. Never had a problem with the way it ran. Except when the bolt that supported the generator and fan broke. Sent the fan into the radiator and made a mess.
That happened on a cold March Sunday morning miles from any towing company. I left the car on road side, hitched a ride to my destination.
A week later I brought a used radiator, fan and necessary tools and fixed the car right on the shoulder, a miserable job in the cold. Merc was soon sold to someone I didn’t know.
Hated adjusting the timing or changing points on my ’46 Mercury, but I made a few bucks when I sold it (in 1960).
Fresh back from the War, Dad picked up a beautiful ’37 ragtop, cream yellow and buckskin. Dashing fellow, my Dad…and although he didn’t keep her very long, that vehicle played a prominent role in his life.
Tooling about near a town name of Bainbridge NY, a good 170 miles south of home, the fuel pump died. Dad said you had to carry a 1/2 – 9/16 combo and a can of welding rod…while he was working on it, a farmer came out to see what was up. His daughter tagged along. Two years later, that beautiful young lady became his wife.
T’were a nice warm March day and he was dressed for the weather. On the way home, zee Franch-Canadiannes sent forth a polar express, as they are wont to do: whiteout, howling winds, plummeting temps. That big 22(?) quart radiator froze up solid somewhere north of Watertown. Sparsely populated area. Poor fellow darn near froze to death before finding a farmhouse…