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

• {'title': 'Hesco throttle bodies', 'url': 'https://www.hescoinc.com/'}

Related

• Throttle Body Bore / Spacer
• HO Upgrade for Renix (Manifold/Injector/PCM Swap)
• All Jeep Cherokee XJ guides & tools
• Browse the full DIY database

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Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.