Secrets of the Buick Nailhead V8

Buick V8 originalThe Buick Nailhead was among the best of the original postwar American V8s—and among the most misunderstood. Here’s the story behind Buick’s powerhouse, including how it earned the name Nailhead. 

 

 

Unlike Cadillac and Oldsmobile, the Buick division of General Motors was in no particular rush to offer an overhead-valve V8 in the postwar era. The Flint brand already had a dependable and refined eight-cylinder engine in its OHV straight eight, which first appeared in 1931. But when it became clear in mid-1950 that the next-generation corporate B-body platform arriving in 1953 would not support the long, heavy straight-eight package, the division was pushed into action.

The Fireball V8 of 1953, soon to become known as the Nailhead, was based on GM’s corporate research efforts, along with Buick’s extensive experience with the straight eight, and with the division’s experiments with narrow-angle V8s. These prototype engines, which employed 22.5 and 35 degree vee angles, offered little packaging advantage over the old straight eight and were soon discarded. While the production Nailhead V8 used a conventional 90-degree bank angle, it offered a number of novel features as well. Let’s dive straight in for a closer look.

 

Buick V8 blackThe original 322 CID, 172 hp V8 that arrived in 1953 set the pattern for all the Buick Nailhead V8 engines to follow through 1966. With its 4.00-in. bore and 3.20-in. stroke, the layout thoroughly embraced GM’s latest short-stroke theories, while generous 4.75-in. bore spacing left plenty of room for future displacement increases up to 425 CID. All versions through ’66 employed forged, fully counterweighted cranks, forged connecting rods, and a 1-2-7-8-4-5-6-3 firing order.

In the cutaway front elevation above, we can see two of the Nailhead’s identifying characteristics: its distinctive vertical valves, their stems at right angles to the pavement, and its underhand-style rocker arms, in which the top of the rocker operates the valve—the opposite of common practice. The lineage of this unusual valvetrain setup is easy to trace.

 

LeSabre and XP-300 engine cutawayThis experimental 215 CID V8 was installed in two famous GM concept cars, the 1951 LeSabre Motorama dream car and the Buick XP-300 roadster. Supercharged, all aluminum, and sporting hemispherical combustion chambers, this engine developed 300 hp. Note the valvetrain linkage for the top (intake) set of valves and rocker arms, similar to that used on the intake valves of the Chrysler Hemi V8. This is essentially the valvetrain layout that would find its way to the Buick production V8, driving both the intake and exhaust valves.

 

Chamber and valvetrain closeupHere’s a closer look at the valvetrain and combustion chamber layout of the production Fireball V8. Note the vertical valves and central spark plug location, providing a tidy pentroof chamber configuration. Buick engineers also took pains to maintain a consistent intake port diameter from the intake manifold flange to the valve seat, in order to maintain uniform airflow velocity. Much of the theory and thinking that went into the Fireball V8 can be found in the 1953 SAE paper 530248, written by Joe Turlay and Verner P. Matthews, two leaders in Buick engine design for many decades.

Intake and exhaust valve diameters on the original 322 CID version were 1.75 inches and 1.25 inches, respectively, while later they were enlarged to 1.875 and 1.50 inches. The relatively small valves and their layout—vertical, in a row, like nails in a plank—generated the familiar Nailhead label, which was never adopted by Buick, needless to say. Official company names included Fireball and Wildcat.

 

cylinder head chamber sideContrary to popular belief, the Buick’s small valves were not an accident or an oversight. They actually had a purpose, enabling a tighter, more efficient combustion chamber. Buick engineers were essentially trading volumetric efficiency and high-rpm capability for combustion and mechanical efficiencies—a worthwhile trade in a road car.

During the straight-eight era, engine development work at Buick had focused on airflow and camshaft lobe design, and the division was confident it could use these tools to provide decent breathing in the new V8 despite the smaller valve area. Ultimately, racers found that the small valves limited the engine’s potential in high-performance, high-rpm applications. But that was little concern to Buick engineers, who were optimizing the engine for smooth, economical operation in large sedans. Coupled to the division’s torque-converter-based Dynaflow automatic transmissions, the Nailhead V8 provided great gobs of torque for silent and effortless performance, exactly as intended.

 

Egge Machine Buick pistonsDomed pistons were required to obtain the desired compression ratio with the fully machined pentroof combustion chambers (photo courtesy Egge Machine Co.) Through the years, the Nailhead was produced in five displacements:

+  The original 322 CID version of 1953-1956 with 4.00 x 3.20-in. bore and stroke.

+   A 264 CID model used only in 1954-1955 Buick Special, with 3.625 x 3.20-in. bore and stroke.

+   The 364 CID V8 produced between 1957 and 1961 with 4.125 x 3.40-in. dimensions.

+   The familiar 401 CID version of 1959 through 1966, with 4.1875-in. bore and 3.64-in. stroke. This engine was used in the 1965 Skylark Gran Sport, though here it was marketed as a “400.”

+   The ultimate nailhead V8, a 425 CID version offered in 1963-1966, with 4.3125-in. bore and 3.60-in. stroke. With optional dual-quad Carter AFB carburetors, it produced 360 hp at 4,400 rpm.

 

Tommy Ivo showboatWhile the Nailhead had its limitations for all-out performance use, it had its successful proponents in racing, including Max Balchowsky of Old Yeller road racing fame and drag racer Tommy Ivo, who learned his Buick engine-building tricks hanging out at Max’s Hollywood shop. TV Tommy’s trademark Model T street roadster ran a Nailhead V8, as did a number of his early dragsters, which sported one, two, and even four Buick V8s. Shown here is Ivo with the Showboat, his four-engined, four-wheel-drive exhibition dragster. (Photo courtesy Tommy Ivo.) 

 

Buick Nailhead V8 street rodWe know what drives the continuing fascination with the Buick Nailhead, espcially among the hot rod crowd: It’s one of the best-looking of the early overhead-valve V8s. The squared-off, vertical valve covers provide a clean, distinctive look, and a full complement of chrome appearance goodies are available.

 

Buick Nailhead turbo with Carter sidedraft carbsThis must be the ultimate expression of Nailhead power, at least from the factory. Buick engineers experimented with this turbocharged 425 CID in the ’60s. Three Carter YH sidedraft carbs fed a single TRW turbo, generating more than 620 lb.-ft. of torque—far more than any Buick driveline could tolerate, so the project was parked. Today the beast resides in the GM Heritage Collection in Sterling Heights, Michigan.

 

15 thoughts on “Secrets of the Buick Nailhead V8

  1. In my earlier days, I had both straight-eight and V8 Buicks, and never felt any lack of power in any of them. The Nailheads were, indeed, smooth and quiet, and as powerful any nearly any other V8 except perhaps the hemis from Chrysler Corp.

  2. One advantage of the “nail” sized valves – high port velocity at low speed for plenty of grunt getting off the mark. I haven’t found any actual measurements, but it was a fairly light valve train compared to the bigger brethren from Cadillac and Olds. The compact dimensions made it one of the easiest engines to fit under the hood of an early Ford – particularly the ’40 which was immortalized by AMT with their classic “Trophy” kit.

  3. Big heavy low rpm slogger. It does not excite me but some of the cars they came in were very nice stylish cars.
    The ‘Fireball’ tag I had never heard before, obviously not paying attention! Chrysler used the Fireball tag on LA 318s late 60s

  4. The Nailhead was no slouch. They found themselves into some GM heavy truck applications as did the Pontiac V8s. They pulled like troopers. On the other hand I was always fascinated with the shape of the Nailhead. I remember custom cars such as the Uncertain T that were powered by the Nailhead. I might add that I have it on good authority that the Uncertain T went like Jack, the Bear…

  5. I was always told that the name “Nailhead” came from the valves being so small they looked like nails, not nails in a plank. I thought Buick also used the name “Fireball” way back in the 30s on there straight eight engines too?

  6. Folks who are into 1/4 mile drives at a time may think the earliest 322’s are slow. But for street use they are more than adequate. My experience with ’65 401’s was much more than adequate. All that matters now is my ’56 Super always results in a huge smile anticipating the next mile!

  7. I have bought a 58 special and removed the heads because of bent valves I measured the head diameter of the exhaust valve and it is 1-7/16 inch but according to specs it is supposed to be 1-1/2 inch any ideas? thanks

    • Could be the valve diameter was reduced via previous valve jobs. With engine wear and with each successive valve job, the valve will be reduced in size and sunk lower in the valve seat.

      • Ive scoured the internet and found no mention of these size valves, the closest being 1-3/8ins for a 264/322 earyl nailhead but the picture shows multiple groove reliefs for collets instead of one continuous groove? Ive now purchased a 1-1/2inch valve and will get it machined. Watch this space

  8. i recently installed a 425 nailhead to my 64 riviera i used the intake manifold from my 64 to the 66 block and the flywheel its running rough the guy i bought it from had receipts from the shop that rebuilt the motor we did a compression check and twopistons had a 50 pounds less than the others my buddy says maybe those pistons havent broken in yet? if u have any answers to my questions i would really appreciate it thamks

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