What Kind of Engines Are Used in NASCAR?

NASCAR’s top series race with naturally aspirated, pushrod V8 engines: the Cup Series uses 358-cubic-inch (5.86 L) purpose-built, fuel‑injected V8s from Chevrolet, Ford, and Toyota; the Xfinity Series runs similar 358‑ci pushrod V8s from team builders or approved spec suppliers; and the Craftsman Truck Series uses a 396‑ci (6.5 L) Ilmor-built spec V8. All are tightly regulated, non‑turbocharged engines designed for durability, parity, and high-revving performance.

NASCAR Cup Series Engines

The modern NASCAR Cup Series “Next Gen” cars are powered by manufacturer-branded, race-only small-block V8s that follow long-standing stock-car traditions—cam-in-block pushrods, two valves per cylinder, and no forced induction—while integrating contemporary control electronics and fuels.

The list below outlines the core technical and regulatory traits of Cup Series engines as they are raced today.

• Architecture: 90-degree, pushrod (OHV) V8, two valves per cylinder; naturally aspirated
• Displacement: 358 cubic inches (5.86 liters), a NASCAR staple since the 1970s
• Fuel system: Electronic fuel injection with a spec control unit; airflow managed by a tapered spacer
• Output: Approximately 670 hp at most tracks; approximately 510 hp at superspeedways under the current rules package
• Materials and construction: Cast-iron blocks with aluminum cylinder heads; dry-sump lubrication
• Fuel: Sunoco Green E15 (gasoline with up to 15% ethanol)
• Operating characteristics: Sustained high-RPM operation (roughly 9,000 rpm peaks) with a rules-defined rev/airflow strategy for reliability and parity

In practice, these specifications balance spectacle and safety: NASCAR manages power and speeds via airflow limitations (tapered spacers) and track-specific aero packages, keeping racing close while preserving engine longevity over 500–600-mile events.

Who Builds Them

Three manufacturers supply Cup Series engines through their factory-affiliated engine shops: Chevrolet (R07 architecture), Ford (FR9), and Toyota (TRD V8). Although they’re branded by automakers, the engines are bespoke racing units—not production road-car engines—designed within NASCAR’s tight dimensional and materials rulebook. Most teams lease powertrains and receive trackside support for builds, updates, and reliability management.

Power Packages and Parity

NASCAR’s current approach sets roughly 670 horsepower at most venues and about 510 horsepower at drafting superspeedways like Daytona, Talladega, and the reconfigured Atlanta. Those numbers are achieved primarily through tapered spacers that curb airflow rather than through displacement or fundamental architecture changes, helping maintain the series’ traditional V8 identity.

NASCAR Xfinity Series Engines

The Xfinity Series runs engines closely related in concept to the Cup powerplants—naturally aspirated 358‑ci pushrod V8s—but teams have options in how they source them, blending cost control with competitive choice.

Here are the key points that define Xfinity power units.

• Architecture and displacement: 358‑ci (5.86 L) pushrod V8s, naturally aspirated
• Sourcing: Teams use either “open” (team/manufacturer-built) engines or NASCAR‑approved sealed/spec engines supplied through approved vendors
• Parity measures: Airflow restrictions (tapered spacers) and sealing programs help contain costs and performance spread
• Performance: Typically in the mid‑600‑horsepower range, depending on package and track
• Fuel and control: NASCAR‑approved Sunoco race fuel with standardized engine management and inspection protocols

This structure preserves the technical DNA fans expect while offering privateer-friendly options that reduce operating costs without sacrificing reliability or raceability.

NASCAR Craftsman Truck Series Engines

The Truck Series uses a single, cost-contained spec engine to ensure parity across the field: the Ilmor 396, a race-purpose pushrod V8 engineered for consistency and long service life under NASCAR’s oversight.

The list below summarizes the Ilmor 396 package.

• Engine: Ilmor 396, 396 cubic inches (6.5 liters), pushrod V8
• Design intent: Spec, sealed engine program focused on reliability, reduced rebuild costs, and competitive balance
• Output: Roughly mid‑600 hp, tailored by NASCAR through airflow and control strategies
• Support: Centralized parts supply, defined maintenance intervals, and technical support to keep budgets predictable
• Fuel: NASCAR‑approved Sunoco racing gasoline under series rules

By standardizing the powerplant, the Truck Series shifts the competitive emphasis to chassis setup, tire management, and driver skill, while safeguarding team budgets.

Shared Design Rules Across NASCAR

Across NASCAR’s top three national series, the engines adhere to common principles aimed at preserving the stock‑car ethos and tight competition.

• Mechanical simplicity: Naturally aspirated, cam-in-block pushrod valvetrains; no turbocharging or supercharging
• Strict rulebook: Fixed displacement ranges, specified materials (e.g., cast-iron blocks), and standardized components where required
• Durability first: Dry-sump lubrication, robust cooling, and conservative airflow limits to survive long-distance races
• Tech oversight: Spec electronics and sealing programs (where applicable) to reduce performance gaps and contain costs
• Fuel continuity: NASCAR-approved Sunoco race fuels, with E15 mandated in the Cup Series

These shared rules maintain the category’s character—high-revving V8s, long green-flag runs—while giving officials levers to manage speeds, reliability, and cost.

Why NASCAR Still Uses Pushrod V8s

Pushrod, two‑valve V8s are part of NASCAR’s competitive identity: they deliver broad, usable torque, spectacular sound, and proven durability. The format also gives officials clear, well-understood parameters to balance performance among manufacturers and teams without escalating costs. While many forms of motorsport showcase overhead-cam or hybrid powertrains, NASCAR prioritizes parity, endurance, and tradition within a modernized rules framework.

The Road Ahead

NASCAR and its manufacturers continue to evaluate future technologies—including advances in fuels and potential electrification or hybrid assistance—through testing and technical collaborations. Any major shift would be introduced deliberately to protect competitive balance and retain the series’ signature V8 character; as of now, the core engine formula described above remains in force.

Summary

NASCAR engines are purpose-built, naturally aspirated pushrod V8s. The Cup Series runs 358‑ci, EFI-equipped, manufacturer-built engines making roughly 670 hp at most tracks (about 510 hp at superspeedways). The Xfinity Series uses similar 358‑ci V8s sourced from team builders or approved spec suppliers, and the Truck Series relies on the Ilmor 396 spec V8 for cost control and parity. Across all three, NASCAR’s rulebook emphasizes durability, close competition, and the traditional V8 experience.