By Alex Chen · July 25, 2026 · 8 min read
TL;DR
S2/S1 power builds: Racing V12. Unbeatable top-end but heavy — only use when you have PI to spare. A class: 6.2L V8 or 2JZ. Best power-to-PI ratio. B class and below: don't swap. Stock engine with bolt-ons is almost always better because swaps cost too much PI at low classes. Fun builds: 4-Rotor Racing. Not the fastest, but the sound alone is worth it.
| Swap | Max HP | Weight | PI Cost | Best For | Tier |
|---|---|---|---|---|---|
| Racing V12 | ~1,850 | Heavy | High | S2, S1 power builds | S |
| 6.2L V8 (LS) | ~1,400 | Mid | Medium | A, S1 all-round | S |
| 3.0L Racing I6 (2JZ) | ~1,200 | Light | Low-Med | A class lightweight builds | S |
| 7.2L Racing V8 | ~1,750 | Heavy | High | S2 American muscle swaps | A |
| 6.5L Racing V12 | ~1,650 | Mid | Medium | S1 handling-power hybrids | A |
| 5.2L V10 (Lamborghini) | ~1,500 | Light | Medium | S1 exotic builds | A |
| 4-Rotor Racing | ~1,100 | Very light | Medium | A class rotary swaps, sound | B |
| 2.0L Turbo I4 (Fusion) | ~800 | Very light | Low | B, C class momentum cars | B |
Racing V12: The big boy. Goes in everything from the Toyota Supra to the Ford Bronco. At 1,850 hp with full upgrades, it turns any car into a missile. The downside is weight — the Racing V12 adds 80-120 lbs to the front axle on most platforms, which kills turn-in on lightweight cars. The PI cost is high enough that you typically can't afford race tires AND max weight reduction AND the V12 in anything below S1. In S2, there's enough PI budget to compensate for the weight with aero and tires. In S1, you're making real compromises. In A class, don't even try.
6.2L V8 (LS): The workhorse. The LS swap is the most versatile engine in FH6 — it goes into over 150 cars, hits 1,400 hp fully built, and the PI cost is manageable in A class and above. It's heavy but not V12-heavy. The soundtrack is a classic American V8 rumble that never gets old. If you're building an all-rounder for A class or S1, the LS is the default choice.
3.0L Racing I6 (2JZ): The tuner's choice. Lighter than the LS, slightly less power (1,200 hp peak), and the PI cost is lower. This is the swap for A-class lightweight builds where every pound matters. Put it in the Toyota GR86, Nissan Silvia S15, or Mazda RX-7 and you get a car that weighs under 2,500 lbs with 800+ hp — absurd power-to-weight. The I6 configuration keeps weight behind the front axle, preserving the car's natural balance better than a V8.
7.2L Racing V8: The American muscle specialist. It's basically the LS swap turned up to 11 — more power, more weight, more PI. Best used in cars that already have heavy V8s (Camaro, Mustang, Challenger) where the weight penalty is negligible because the chassis was designed for a big engine. Hits 1,750 hp and sounds like an NHRA dragster. Excellent for S2 drag builds.
6.5L Racing V12 (Lamborghini-derived): The refined alternative to the Racing V12. Less peak power (1,650 hp) but a wider, smoother powerband. Where the Racing V12 hits hard at the top end and feels dead in the mid-range, the 6.5L pulls cleanly from 3,000 rpm to redline. It's the better choice for S1 builds that need both speed and corner exit traction. Lighter than the Racing V12, too.
5.2L V10 (Lamborghini): The sweet spot for exotic S1 builds. 1,500 hp is plenty for S1 — the class PI cap means you can't use 1,800 hp anyway. The V10 is lighter than any V12 and has the best throttle response of any 1,000+ hp swap. Sounds incredible. If you're building a Ferrari, Lamborghini, or Audi R8 for S1 online racing, this is usually the right choice over the V12.
4-Rotor Racing: Objectively not the fastest swap. Maxes out around 1,100 hp and the PI cost is medium-high. But the sound — a screaming 10,000-rpm rotary howl — makes every car feel like a 787B Le Mans prototype. Put it in a Mazda Miata and you have the most entertaining A-class car in the game, even if it's not the absolute fastest.
2.0L Turbo I4 (Fusion): The low-class specialist. Only 800 hp fully built, but the weight savings compared to stock engines on classic cars can be 200+ lbs. That weight reduction can be worth more lap time than the power gain from a bigger swap in B and C class where corners matter more than straights. Also, the idea of a 2.0L turbo 4-cylinder in a '69 Charger is deeply funny.
Stock engines are underrated. On many cars — particularly modern performance cars that already have powerful, lightweight engines — the stock engine with full bolt-ons (race cams, turbo/supercharger, intake, exhaust, displacement upgrade) gets you to within 100-150 hp of a swap for half the PI. That saved PI goes into tires, weight reduction, and aero — all of which translate more directly to lap time than peak horsepower on most tracks.
The cars where you should almost never swap: any modern Ferrari (the stock V8s and V12s are already optimized for the chassis), the Porsche 911 GT3 RS (the stock flat-6 is perfectly balanced), and anything with a mid-engine layout under 3,000 lbs. A swap will make these cars heavier and worse-balanced without enough power gain to justify it.
Not every build is about lap times. Some swaps are worth it just for the auditory experience: the 4-Rotor Racing transforms any car into a rotary banshee; the 7.2L Racing V8 sounds like a NASCAR stock car; the 5.2L V10 produces a Lamborghini wail that turns heads in free roam. If you're building a cruiser or a drift car rather than a competitive racer, prioritize sound over peak performance.
PI cost varies by car (swapping a V12 into a lightweight Miata costs more PI than into a heavy muscle car), but here are approximate averages:
| Swap | Avg PI Cost | Min Class Viable |
|---|---|---|
| Racing V12 | 60-95 | S1 |
| 6.2L V8 | 40-65 | A |
| 3.0L I6 (2JZ) | 30-50 | A |
| 7.2L Racing V8 | 55-85 | S1 |
| 6.5L Racing V12 | 50-75 | S1 |
| 5.2L V10 | 45-70 | S1 |
| 4-Rotor Racing | 35-55 | A |
| 2.0L Turbo I4 | 15-30 | B |