Professional 13B-REW Rotary Engine Rebuild for Mazda RX-7 FD3S

Overview: Why Rebuild a Rotary Engine?

The Mazda RX-7 FD3S's 13B-REW twin-rotor engine is legendary for its high-revving character and compact design, but it requires periodic rebuilding due to apex seal wear, carbon buildup, and compression loss. A proper rebuild restores power, improves reliability, and can support higher boost levels for modified applications.

Typical Rebuild Intervals:

• Stock Power (255 hp): 80,000-120,000 miles
• Moderate Mods (350-400 hp): 40,000-60,000 miles
• High Power (500+ hp): 20,000-40,000 miles

Signs You Need a Rebuild:

• Compression below 90 psi on any rotor face
• Hard starting (especially when hot)
• Excessive oil consumption (>1 quart per 1,000 miles)
• Loss of power above 5,000 RPM
• Coolant mixing with oil (coolant seal failure)

Prerequisites

Before starting, ensure you have:

• Compression test results (document baseline)
• Clean engine bay (pressure wash before disassembly)
• Factory service manual (Mazda FSM or Racing Beat guide)
• Organized parts storage (label baggies for bolts/clips)
• Digital camera (photograph everything during disassembly)

Installation Steps

Follow these steps precisely. Rotary engines require exact tolerances and cleanliness.

Step 1: Engine Removal

Remove the 13B-REW from the FD3S chassis. Disconnect battery, drain fluids, unbolt motor mounts, transmission, exhaust, and wiring harness. Use an engine hoist with load leveler.

Critical: Support transmission separately before unbolting from engine. Mark all vacuum lines and electrical connectors with tape labels.

Time Estimate: 4-6 hours

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Step 2: External Component Removal

Strip all external components from the engine block: alternator, water pump, oil metering pump (OMP), fuel rail, intake manifold, turbos, exhaust manifolds, clutch/flywheel.

Organize parts into labeled containers by system (cooling, ignition, fuel, turbo). Clean each part with brake cleaner and inspect for wear.

Time Estimate: 2-3 hours

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Step 3: Front Cover and Eccentric Shaft Removal

Remove the front cover (14mm bolts) and eccentric shaft pulley bolt (requires 54mm socket and breaker bar). Remove oil pump and front stationary gear.

Critical: The eccentric shaft pulley bolt is extremely tight (289-362 lb-ft torque). Use a 6-foot breaker bar or impact gun. Do NOT damage the keyway.

Time Estimate: 1-2 hours

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Step 4: Rear Cover and Flywheel Removal

Remove the rear stationary gear and rear cover. Pull the eccentric shaft out from the rear (requires gentle tapping with rubber mallet).

Warning: The eccentric shaft weighs ~15 lbs and is precision-balanced. Do NOT drop or strike it. Inspect bearing journals for scoring.

Time Estimate: 1 hour

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Step 5: Intermediate Housing Disassembly

Separate the intermediate housing from the front rotor housing. Remove the 10mm tension bolts in a crisscross pattern (reverse of torque sequence).

Critical: The intermediate housing is aluminum and warps easily. Support it evenly on wood blocks during removal. Check for warpage with a straightedge (max 0.002" allowed).

Time Estimate: 1 hour

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Step 6: Front Rotor and Housing Removal

Lift the front rotor off the eccentric shaft. Remove the front rotor housing.

Inspection Points:

• Apex seals: Check for chipping, cracking, or excessive wear (replace if <0.120" tall)
• Side seals: Check for wear grooves (replace if >0.004" deep)
• Corner seals: Check for rounding (replace if chamfer exceeds 0.020")
• Rotor housing chrome: Check for scoring, discoloration, or pitting (resurface if damaged)

Time Estimate: 1 hour

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Step 7: Rear Rotor and Housing Removal

Repeat the process for the rear rotor and housing. Lay all parts on clean shop towels in disassembly order.

Organization Tip: Take photos at each stage. Rotary engines have specific orientation for all seals and springs.

Time Estimate: 1 hour

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Step 8: Rotor Housing Inspection and Resurfacing

Inspect the chrome-plated rotor housings for wear. Minor scoring (<0.003" deep) can be polished out with 600-grit sandpaper. Deep scoring requires professional resurfacing or replacement.

Professional Service: Rotor housing resurfacing costs $150-$250 per housing and removes 0.005-0.010" of material to restore smoothness.

Time Estimate: 2-4 hours (if DIY polishing) or send out for professional service

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Step 9: Eccentric Shaft Bearing Inspection

Inspect all four main bearings on the eccentric shaft. Check for scoring, discoloration, or excessive play. Measure bearing clearances with Plastigage (spec: 0.0016-0.0028").

Replacement: If clearances exceed 0.0035", replace bearings (requires hydraulic press and heating rotor housings to 250°F for installation).

Time Estimate: 2-3 hours (if replacing bearings)

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Step 10: Rotor Cleaning and Inspection

Clean both rotors with brake cleaner and compressed air. Remove all carbon deposits from rotor faces and oil passages. Inspect for cracks, warpage, or excessive side clearance.

Clearance Check: Measure side clearance between rotor and side housing with feeler gauges (spec: 0.0047-0.0083"). Replace rotors if clearance exceeds 0.010".

Time Estimate: 2 hours

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Step 11: Apex Seal, Corner Seal, and Side Seal Installation

Install new apex seals, corner seals, and side seals in each rotor. Use Mazda OEM seals or Racing Beat high-performance seals for boosted applications.

Critical Assembly Steps:

1. Clean all seal grooves with brake cleaner
2. Install springs first (apex seal springs, side seal springs)
3. Install seals with chamfered edge facing combustion chamber
4. Check that seals move freely in grooves (no binding)
5. Apply thin coat of engine assembly lube to seal faces

Torque Spec: Apex seals should have 0.002-0.006" side clearance in groove (check with feeler gauge)

Time Estimate: 3-4 hours (patience required)

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Step 12: Oil Seal Replacement

Replace all oil control rings (O-rings) on both rotors. Use Viton O-rings for high-temp applications (required for turbo engines).

Installation: Lube O-rings with clean engine oil before installation. Ensure they seat fully in grooves without twisting.

Time Estimate: 1 hour

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Step 13: Rotor Housing Reassembly Preparation

Clean all mating surfaces on rotor housings, intermediate housing, and side housings with brake cleaner. Apply thin coat of Permatex Aviation Form-A-Gasket to both sides of all gaskets.

Gasket Kit: Use genuine Mazda gasket kit or Racing Beat performance gasket set (includes all seals, O-rings, and gaskets for complete rebuild).

Time Estimate: 1 hour

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Step 14: Front Rotor and Housing Assembly

Install the front rotor housing onto the intermediate housing. Slide the front rotor onto the eccentric shaft (align apex seals with rotor housing chrome surface).

Critical: Rotate the eccentric shaft slowly while installing the rotor to ensure apex seals don't catch on housing edges. Listen for any scraping sounds (indicates misalignment).

Time Estimate: 1-2 hours

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Step 15: Intermediate Housing and Rear Rotor Assembly

Install the intermediate housing over the front rotor. Install the rear rotor onto the eccentric shaft. Slide the rear rotor housing over the rear rotor.

Alignment: Use alignment dowels to ensure housings seat correctly. Do NOT force housings together (indicates seal misalignment).

Time Estimate: 1-2 hours

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Step 16: Tension Bolt Installation and Torque Sequence

Install the 6mm tension bolts through all housings in the correct torque sequence (start from center, work outward in a star pattern). Torque in three stages:

1. Stage 1: 15 lb-ft
2. Stage 2: 25 lb-ft
3. Stage 3: 35 lb-ft (final torque)

Critical: Follow the factory torque sequence exactly to prevent housing warpage. Let the engine sit for 30 minutes between stages.

Time Estimate: 1 hour

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Step 17: Front and Rear Cover Installation

Install the front and rear stationary gears, oil pump, and front/rear covers. Torque all bolts to Mazda specifications (varies by bolt size, see service manual).

Seal Application: Use Permatex Ultra Grey RTV on front and rear cover mating surfaces (1/8" bead). Let RTV cure for 1 hour before adding oil.

Time Estimate: 2 hours

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Step 18: Eccentric Shaft Pulley and Flywheel Installation

Install the eccentric shaft pulley (front) and flywheel (rear). Torque the eccentric shaft pulley bolt to 289-362 lb-ft using a torque wrench and 54mm socket.

Locking Method: Use the factory flywheel holder tool or wedge a large screwdriver between flywheel teeth and bellhousing to prevent rotation during torque.

Time Estimate: 1 hour

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Step 19: External Component Reinstallation

Reinstall all external components in reverse order of removal: alternator, water pump, oil metering pump (OMP), fuel rail, intake manifold, turbos, exhaust manifolds.

OMP Setting: Adjust the oil metering pump to factory spec (or increase by 20% for modified engines). Verify oil flow through injector nozzles before starting engine.

Time Estimate: 3-4 hours

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Step 20: Engine Reinstallation into FD3S Chassis

Reinstall the rebuilt engine into the RX-7 chassis. Reconnect motor mounts, transmission, exhaust, wiring harness, and all vacuum lines.

Double-Check: Verify all electrical connectors are seated, no vacuum leaks, coolant hoses clamped, and oil filter installed.

Time Estimate: 4-6 hours

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Step 21: Fluid Fill and Pre-Start Checks

Fill engine with break-in oil (10W-30 conventional oil + 1 bottle of ZDDP additive). Fill coolant system with 50/50 mix of distilled water and coolant.

Pre-Start Checklist:

• Oil level at full mark
• Coolant filled and bled (no air pockets)
• Battery connected and charged
• Fuel system primed (turn key to ON for 10 seconds, 3 times)
• No fluid leaks visible

Time Estimate: 1 hour

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Step 22: Initial Start and Break-In Procedure

Start the engine and let it idle for 20 minutes. Monitor oil pressure (should be 60+ psi at idle when cold, 25+ psi when hot).

Break-In Rules:

• First 500 miles: No sustained WOT, vary RPM between 2,500-5,500, avoid lugging below 2,000 RPM
• 500-1,000 miles: Gradually increase RPM range, one or two 7,000 RPM pulls per drive
• After 1,000 miles: Change oil and filter, compression test, then drive normally

Critical: Do NOT exceed 4,500 RPM during the first 500 miles. Apex seals need time to seat against the rotor housing chrome.

Time Estimate: 20 minutes (initial start), ongoing break-in

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Step 23: Compression Test and Verification

After the first 500-mile break-in, perform a hot compression test. Target compression: 100-120 psi on all six rotor faces (three per rotor).

Acceptable Variation: Max 10 psi difference between any two faces. If variation exceeds 15 psi, reseat apex seals by running WOT pulls.

Time Estimate: 30 minutes

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Step 24: Dyno Tuning (Modified Engines Only)

If you installed upgraded components (larger turbos, fuel system, etc.), schedule a professional dyno tune to optimize fuel and ignition maps.

Tuning Requirements:

• Standalone ECU (Haltech, AEM, or Link G4+)
• Wideband O2 sensor for AFR monitoring
• Knock detection system (rotaries are sensitive to detonation)

Estimated Cost: $800-$1,200 for professional dyno tune

Time Estimate: 4-6 hours (dyno shop)

Parts Required

1. Complete Rotary Rebuild Kit (Mazda OEM or Racing Beat)

   • Quantity: 1
   • Price: $1,200-$1,800
   • Includes: Apex seals, side seals, corner seals, springs, O-rings, gaskets

2. Eccentric Shaft Bearings (if replacing)

   • Quantity: 1 set (4 bearings)
   • Price: $300-$500

3. Coolant Seal O-Rings (Viton high-temp)

   • Quantity: 1 set
   • Price: $50-$80

4. Engine Assembly Lube

   • Quantity: 1 tube
   • Price: $15-$25

5. Break-In Oil (10W-30 conventional + ZDDP additive)

   • Quantity: 6 quarts oil + 1 bottle ZDDP
   • Price: $40-$60

6. RTV Sealant (Permatex Ultra Grey)

   • Quantity: 2 tubes
   • Price: $20-$30

Tools Required

1. Engine Hoist with Load Leveler

   • Rental Cost: $75/day

2. Torque Wrench Set (10-150 lb-ft range)

   • Must have for tension bolt torque sequence

3. 54mm Socket (for eccentric shaft pulley bolt)

   • Deep-well impact socket recommended

4. Feeler Gauge Set (0.001-0.025")

   • For clearance checks

5. Plastigage Kit

   • For bearing clearance measurement

6. Digital Caliper (0.001" resolution)

   • For seal and rotor measurements

7. Compression Tester (rotary-specific)

   • Standard piston compression tester will NOT work

Common Issues and Warnings

Warning 1: Apex Seal Installation

• Apex seals are brittle and can chip if dropped or mishandled
• Always install with chamfered edge facing combustion chamber
• Check that seals move freely in grooves (no binding)

Warning 2: Carbon Seal (Oil Control Ring)

• Install carbon seal springs correctly (convex side up)
• Lube all O-rings before installation to prevent tearing

Warning 3: Housing Warpage

• Never overtighten tension bolts (max 35 lb-ft)
• Follow torque sequence exactly to prevent intermediate housing warpage

Warning 4: Coolant Seal Failure

• Most common cause of rotary failure after rebuild
• Use Viton O-rings (not standard rubber) for high-temp durability
• Inspect coolant passages for corrosion before reassembly

Expected Results

After a proper rebuild and break-in:

• Compression: 100-120 psi on all rotor faces
• Oil Consumption: 1 quart per 3,000-5,000 miles (normal for rotary)
• Power: Factory 255 hp (stock) or higher if modified
• Reliability: 80,000-120,000 miles before next rebuild (stock power)

Maintenance After Rebuild

• Oil Changes: Every 3,000 miles (rotaries are hard on oil)
• Coolant Flush: Every 30,000 miles (prevent corrosion)
• Spark Plugs: Every 20,000 miles (NGK BUR9EQ recommended)
• Air Filter: Every 15,000 miles
• Compression Test: Every 30,000 miles (early warning system)

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Disclaimer: This is a complex rebuild requiring mechanical expertise. If you are not comfortable with engine disassembly, consult a rotary specialist shop (Mazda dealer, Racing Beat, Defined Autoworks, etc.). Improper assembly can cause catastrophic engine failure.