Wildcat 445 401
1959–1966325 hp / 445 lb-ft representative
Signature four-barrel 401, named for its torque rating
Buick 401 Nailhead / Wildcat 445 enginePhoto: Mr.choppers — CC BY-SA 3.0 — via Wikimedia Commons · CC BY-SA 3.0
Buick · Nailhead V8
Buick 401 Nailhead / Wildcat 445
The high-torque Nailhead that powered Wildcats, Rivieras and the first Buick Gran Sport.
401
Cubic inches
The 401 became the best-known high-performance Nailhead, using huge low-speed torque to power the Riviera and the 1965 Skylark Gran Sport before Buick replaced the Nailhead with a new big-block family.
Key variants
All variantsWildcat 445 401Skylark GS '400' 401
Displacement
401 ci
Bore
4.1875"
Stroke
3.64"
Years
1959–1966
Key Takeaway
The 401 paired a 4.1875-inch bore with a 3.64-inch stroke and became the best-known large-displacement Nailhead. Its nearly vertical valves limited ultimate airflow but helped create a narrow engine with exceptional low-rpm torque.
Technical Specifications
- Compression
- 10.25:1 in documented 1964–1965 Wildcat 445 specification
- Horsepower
- 325 hp gross in documented four-barrel specification
- Torque
- 445 lb-ft gross
- Architecture
- 90-degree OHV V8
- Block
- Cast iron
- Cylinder heads
- Cast iron
- Valvetrain
- Pushrod OHV with hydraulic lifters
- Aspiration
- Naturally aspirated
- Fuel delivery
- Four-barrel carburetion in Wildcat 445 performance form
- Firing order
- 1-2-7-8-4-5-6-3
- Main bearings
- 5
The 401 paired a 4.1875-inch bore with a 3.64-inch stroke and became the best-known large-displacement Nailhead. Its nearly vertical valves limited ultimate airflow but helped create a narrow engine with exceptional low-rpm torque.
Internal Specifications
Variant-specific values are labeled. Engine families that span multiple years or RPOs can have different heads, cams, induction and rotating parts, so the exact code/year always takes priority.
Identification & Output
- Engine codes / RPO
- 4F / 4G (1959–1960 401 references), 4H (1961 401), KT (1964 401), MT (1966 standard 401 Wildcat 445), MR (1966 GS '400' 401)
- Casting numbers
- 1185404 / 1185484 / 1345404 / 1346046 / 1349046 / 1364714 (representative 401 block references), 1185485 / 1190415 / 1196914 / 1374603 (401/425 head references)
- Power rating
- SAE gross / period brake horsepower
- Horsepower RPM
- 4400 rpm
- Torque RPM
- 2800 rpm
Rotating Assembly
- Rod length
- 6.220 in
- Deck height
- Approximately 10.0 in
Operating Specs
- Production notes
- The 401 appeared for 1959 with a 4.1875-inch bore and 3.64-inch stroke. Buick’s 'Wildcat 445' name referred to its 445-lb-ft torque rating, not displacement.
Compatibility Notes
- 401 and 425 share much of the late Nailhead architecture, but bore, pistons and application-specific induction differ; verify block casting and production code.
- The 1965–1966 Skylark GS '400' is still a 401-cid Nailhead. Do not confuse it with Buick’s unrelated 400-cid big-block introduced for 1967.
Notable Applications
Buick RivieraBuick WildcatBuick Electra1965–1966 Buick Skylark Gran Sport
Strengths
- 445 lb-ft factory torque rating in Wildcat 445 form
- Compact big-displacement packaging
- Iconic Riviera and Gran Sport history
Weaknesses / Watch-outs
- Cylinder-head airflow limits very high-rpm naturally aspirated builds
- Nailhead-specific transmission and accessory details require swap planning
Common Upgrades
- Dual-quad induction
- Custom headers
- Modern valvetrain upgrades
Racing History & Legacy
The 401’s abundant low-speed torque made it popular in drag racing and customs, while Buick used GS versions to enter the muscle-car market before the newer 400/430 big-block family arrived.
The 401 is the quintessential street-performance Nailhead.
References & Image Credit
Engine image: Mr.choppers — CC BY-SA 3.0 — via Wikimedia Commons · CC BY-SA 3.0 · source
Team Buick 401/425 factory specifications
technical reference
1965 Buick technical specifications
period spec
Team Buick — 401/425 Nailhead specifications
technical reference
Team Buick — Nailhead block/head casting numbers
technical reference
Team Buick — U.S. Buick engine production codes
identification reference
Key Factory / Build Variants
Skylark GS '400' 401
1965–1966Application dependent; 325–340 hp documented
Performance A-body version marketed as 400 for GM displacement-policy reasons
Engineering Notes Worth Knowing
01
401 cu in / 6.6 L with 4.1875 x 3.64-inch bore and stroke.
02
90-degree OHV Nailhead V8 with hydraulic lifters.
03
Wildcat 445 form used four-barrel carburetion and about 10.25:1 compression.
04
Factory rating: 325 hp gross and 445 lb-ft gross.
History · context · related reading
The Story Behind Buick 401 Nailhead / Wildcat 445
Buick advertised the 401 by its torque number—Wildcat 445—because torque was the whole point. The engine delivered effortless shove in Rivieras, Wildcats, Electras, and early Gran Sports.
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