© 2026 by CTR ESB President and Webmaster J. W. Howland
CAPITAL TRIUMPH REGISTER
MIDATLANTIC CHAPTER
OF THE
Vintage Triumph Register
CAPITAL REGION LOCAL CHAPTER
OF THE
TRIUMPH REGISTER OF AMERICA
copyright protected
CTR EVENTS
Heading 4
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Jun 1 - Deadline for the June issue of The Standard
Jun 6 - CTR Spring Rally *CTR*
Jun 13 (New date) - Coffee and Donuts in the Park *CTR*
Jun 15-19 - All Triumph Drive In & TRA National Meet, Madras, OR *CTR*
Jun 21 - Sully Antique Car Show, Chantilly, VA *CTR*
Jun 28 - Original British Car Day, Mount Airy, MD *CTR*
Jun 27 - Get Your Hands Dirty: Art Fournier’s Spitfire *CTR*
Jun 28 - Original British Car Day, Mount Airy, MD *CTR*
Jul 11 - CTR Breakfast, Jukebox Diner, Annandale, VA *CTR*
First and Third Saturdays, 7:00-9:00 a.m., Clifton Classic, Clifton, VA
First and Third Sundays - 8:00-10:00 a.m., Hollin Hall Cars and Coffee, Alexandria, VA
First Wednesdays Jun-Oct - 5:00-7:00 p.m., Cars & Cigars, Brookeville, MD
Fridays, 4:00-7:00 p.m., Laytonsville, MD, Cruise In at Julianos Pizza
Saturdays, 8:00-10:00, Corner Bakery Cars and Coffee, Bethesda, MD
Saturdays, 6:00-9:00 a.m., Katie’s Cars and Coffee, Great Falls, VA
Saturdays, 9:00-11:00 a.m., Coffee in the Barn, Classic Motor Museum, St. Michaels, MD, $5.00
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Basic Tuning Manual for
Triumph 4- and 6-Cylinder Engines
​
Baby-Step Procedures for TR2–TR6 Owners
1. Philosophy of Tuning
A Triumph engine should always be tuned in this order:
1. Mechanical condition
2. Valve adjustment
3. Ignition system
4. Carburetors
5. Final road tuning
Do NOT start by adjusting carburetors first.
Most poor-running Triumphs are actually ignition problems, vacuum leaks, incorrect valve lash, or timing issues.
2. Basic Tools Needed
Essential Beginner Tools:
• Timing light
• Feeler gauges
• Compression tester
• Dwell meter (optional)
• Vacuum gauge
• Carb synchronizer
• Flat screwdrivers
• Tachometer
• Spark plug wrench
3. Step 1 — Mechanical Health Check
Before tuning, perform a compression test.
Typical healthy compression:
• 4-cylinder TR engines: 140–180 psi
• 6-cylinder TR engines: 130–170 psi
Cylinders should be within about 10% of each other.
4. Step 2 — Adjust Valves (Baby Steps)
Typical cold valve lash:
4-Cylinder Triumphs:
• Intake: 0.010"
• Exhaust: 0.012"
6-Cylinder Triumphs:
• Usually 0.010"
Always verify your camshaft specifications.
5. Rule of 9 (4-Cylinder Engines)
When one valve is fully open, adjust the valve whose number adds to 9.
Example:
• Valve 1 open → adjust valve 8
• Valve 2 open → adjust valve 7
6. Rule of 13 (TR250/TR6)
When one valve is fully open, adjust the valve whose number adds to 13.
Example:
• Valve 1 open → adjust valve 12
• Valve 2 open → adjust valve 11
7. Step 3 — Ignition System Tuning
Inspect:
• Spark plugs
• Plug wires
• Distributor cap
• Rotor
• Coil
• Points (if equipped)
8. Spark Plug Basics
Typical spark plug gaps:
• Points ignition: 0.025"
• Electronic ignition: 0.030–0.035"
Plug color meanings:
• Light tan = Good
• White = Lean
• Black soot = Rich
• Oily = Oil burning
9. Setting Ignition Timing
Typical initial timing:
• TR2/TR3: 4–8° BTDC
• TR4/TR4A: 8–12° BTDC
• TR250/TR6: 10–14° BTDC
Modified engines often prefer more advance.
10. Timing Procedure (Baby Steps)
1. Warm engine
2. Connect timing light
3. Loosen distributor clamp slightly
4. Aim light at timing marks
5. Rotate distributor slowly
6. Tighten clamp
7. Recheck idle speed
11. Mechanical Advance Check
Timing should smoothly advance with RPM.
If timing jumps:
• Distributor weights may stick
• Springs may be worn
• Shaft bushings may be loose
12. Step 4 — Carburetor Basics
Goals:
• Smooth idle
• Clean acceleration
• No hesitation
• Light tan spark plugs
13. SU Carburetor Tuning
Baby-Step SU Setup:
1. Set idle screws equally
2. Synchronize airflow
3. Adjust mixture nuts equally
4. Lift piston slightly to check mixture response
14. Stromberg Carburetors
Common issues:
• Vacuum leaks
• Torn diaphragms
• Warped bodies
Always inspect diaphragms first.
15. Weber DCOE Tuning Basics
Popular Weber sizes:
• DCOE38
• DCOE40
• DCOE45
16. Typical Weber Starting Points
TR4 (DCOE38):
• Choke: 30 mm
• Main jet: 115–125
• Idle jet: 50F9
TR250/TR6 (DCOE40):
• Choke: 32–34 mm
• Main jet: 125–135
• Idle jet: 50F9
17. Synchronizing Weber Carburetors
1. Disconnect linkage
2. Set idle screws equally
3. Measure airflow barrel-to-barrel
4. Adjust each carb slowly
5. Reconnect linkage carefully
18. Idle Mixture Tuning
Turn each mixture screw slowly inward and outward.
Find highest smooth idle, then slightly lean the mixture.
19. Vacuum Leak Checks
Check:
• Manifold gaskets
• Throttle shafts
• Brake booster lines
• Carb mounting flanges
Spray carb cleaner carefully near joints to locate leaks.
20. Typical Triumph Idle Speeds
• TR2/TR3: 700–800 RPM
• TR4/TR4A: 800–900 RPM
• TR250/TR6: 850–950 RPM
Performance cams may require higher idle speeds.
21. Road Test Tuning
Test under:
• Light throttle
• Cruise
• Acceleration
• Uphill loads
Listen for pinging, popping, or hesitation.
22. Reading Engine Symptoms
• Backfire through carbs = Lean
• Black smoke = Rich
• Hesitation = Lean transition
• Pinging = Too much timing
• Hard hot start = Too much advance
23. Performance Camshaft Notes
Common cams:
• 260°
• 270°
These often require:
• Richer idle
• More ignition advance
• Higher idle RPM
24. Header and Exhaust Tuning
Headers improve:
• Breathing
• Midrange torque
• High RPM power
Common designs:
• 4:1
• 6:3:1
• 4-2-1
25. Fuel Recommendations
Older Triumphs generally prefer ethanol-free fuel when possible.
Higher compression engines may require premium fuel.
26. Final Beginner Advice
Change only ONE thing at a time.
Do not change jets, timing, plugs, and linkage simultaneously.
27. Recommended Beginner Sequence
1. Compression test
2. Valve adjustment
3. Ignition tune-up
4. Timing adjustment
5. Carb synchronization
6. Mixture tuning
7. Road test
8. Spark plug reading
28. Most Common Triumph Problems
4-Cylinder Cars:
• Throttle shaft wear
• Distributor wear
• Vacuum leaks
6-Cylinder Cars:
• Stromberg diaphragm leaks
• Distributor advance wear
• Carb synchronization issues
29. Best Beginner Upgrades
Reliability Upgrades:
• Electronic ignition
• Modern fuel hose
• Aluminum radiator
Performance Upgrades:
• Mild 260 cam
• Header
• Weber DCOEs
• Overdrive transmission
30. Final Thoughts
Triumph engines are simple, durable, and very tuneable.
A properly tuned Triumph should:
• Idle smoothly
• Pull strongly
• Run cool
• Sound excellent
Take tuning slowly — small adjustments make a big difference.
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