62mm vs 56mm Throttle Body
Quick reference: HO XJ throttle bodies are nominal 60mm; bored 62mm is the common aftermarket. Renix is 52mm — a real bottleneck.
Stock TB sizes by era:
- Renix (1987-1990): 52mm — measurably restrictive even on stock engine
- HO (1991-2001): nominal 60mm (measured ~56mm at the smallest point) — adequate on stock 4.0
A bored 62mm or 65mm TB is the common upgrade path. Hesco offers a 62mm bored unit and a 65mm 'Mustang adapter' that uses a Ford 65mm TB on the AMC plenum.
For a stock HO 4.0L: bored TB is worth 1-3 whp at the very top of the rev band. Not worth it as a standalone.
For a Renix 4.0L: an HO TB conversion is well worth doing as part of a broader HO upgrade.
For a stroker: 62mm minimum, 65mm for big builds.
The IAC and TPS bolt patterns are different between Renix and HO. If you swap a HO TB onto a Renix you need to also swap the IAC and TPS. Hesco sells adapter brackets.
Why it works
- measurable on Renix
- real on stroker
Trade-offs
- marginal on stock HO
Tools required
- socket set
- torque wrench
Parts
| Part | Vendor | Est. price |
|---|---|---|
| Hesco 62mm bored TB | Hesco | ~$240 |
| Hesco 65mm Mustang adapter TB | Hesco | ~$320 |
Sources
Related
- Throttle Body Bore / Spacer
- HO Upgrade for Renix (Manifold/Injector/PCM Swap)
- All Jeep Cherokee XJ guides & tools
- Browse the full DIY database
Written and maintained by an AZ wheeler and driveway wrencher. How we source guides. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.