VQ37VHR Swap in a 2003 Nissan 350Z NASA ST4 Race Car

I’ve owned this 2003 Nissan 350Z since 2004. What began as a weekend street car eventually evolved into a dedicated NASA Super Touring 4 (ST4) race car after years of autocross, HPDE, and competition use.

After blowing two VQ35DE engines and reaching the practical performance limit of that platform, I decided it was time for a major change: a VQ35DE to VQ37VHR engine swap.

This post documents the reasoning behind the swap, the parts involved, and the dyno results from the completed build.

SOHO Promo – https://www.youtube.com/watch?v=XoXtsRxpg-A

More photos of the swap

Why Swap the VQ35DE?

Despite extensive development, the VQ35DE has a clear ceiling for naturally aspirated racing applications. Even well-built examples struggle to exceed 275-300 wheel horsepower, and oiling reliability becomes a serious concern during long road race sessions.

After losing engines in both 2021 and 2024 — even with oiling upgrades — it became clear that continuing with the DE platform wasn’t sustainable for competitive ST4 racing.

At the same time, competitors in the class were fielding cars with stronger midrange and top-end power. The solution wasn’t more tuning — it was a better engine.

Why the VQ37VHR Is a Better Road Racing Engine

The VQ37VHR, originally found in the Nissan 370Z, offers several advantages over the VQ35DE:

Larger 3.7L displacement
VVEL variable valve lift
Higher usable RPM range
Stronger torque curve across the band

For a road race car, these traits matter more than peak power. The VQ37 provides consistent pull, improved throttle response, and better power delivery exiting corners — all critical in NASA ST4 competition.

The Swap Process & Shop Choice

The swap was completed by SOHO Motorsports in Charlotte, NC. From intake to ECU calibration, the project required custom wiring, ECU integration, and extensive testing.

This is not a bolt-in swap. The mechanical installation is not straightforward, so I elected SOHO to do the swap so I could be confident when I go back on track.

VQ37VHR Swap Parts List

Engine & Electronics

VQ37VHR engine (370Z)
VQ37 manual transmission
Custom engine wiring harness
370Z ECU with EcuTek tuning

Intake, Exhaust & Oiling

SOHO Motorsports VHR intake
PPE long tube headers
Z1 active baffled oil pan
ATI Super Damper crank pulley

Clutch & Reliability

ZSpeed Quickshift clutch package
CSC delete kit

All components were selected with endurance and road racing reliability as the priority.

Dyno Results: VQ37VHR in a 350Z

On 93 octane pump gas, the naturally aspirated VQ37VHR produced:

350 horsepower –
284 lb-ft of torque

Peak power occurs around 7,500 RPM, with a smooth pull to an 8,000 RPM redline. Compared to the VQ35DE, the improvement is immediate and substantial across the entire rev range.

For competition use, a NASA ST4 / TT4 compliant tune was also created, limiting output to 318 horsepower while preserving the engine’s broader torque curve.