How to Fine Tune Timing on a Triumph TR6

I tend to be the kind that would assume that simply setting timing to the factory specification will give optimum performance and economy.  I have learned that octane levels have changed since the 70s, carb settings, engine wear, distributor wear or unique characteristics of a rebuilt distributor, all impact where optimal timing should be set.  If timing is set too retarded, the engine won’t pull enough vacuum, resulting in an overly rich burn.  If timing is too far advanced, the engine will experience pre-detonation and possible valve damage and power loss.

Before you can fine tune timing, some basic fundamentals must be right:

  1. The crank and cam are correctly in sync, chain not overly worn, tensioner in good shape.
  2. Had distributor rebuilt by including adding the adjusting wheel, specifications at 12-15° before TDC with vacuum disconnected and plugged.
  3. Ignition components are good  – I installed top quality new coil/points/condenser/rotor/cap/wires/plugs from
  4. Vacuum leaks – I changed all vacuum hoses including the brake booster vacuum line.
  5. Compression is good – 160 on all cylinders
  6. Carbs are in good condition:  Verify no leak in piston diaphragms, healthy air bypass diaphragms.  I had to put new air bypass diaphragms and gaskets in both carbs, screw turned counterclockwise all the way to block off air bypass per Joe Curto.
  7. Decide what gas you will burn most often, and fill the tank.  I decided on Premium.

Steps to Fine Tune Timing

  1. Set valves to .010 with engine cold assuming a stock cam.
  2. Set Dwell to 35° ± 3°
  3. Set timing adjuster wheel on distributor to middle position
  4. Set timing to 15° before TDC with Timing Light, vacuum disconnected and plugged at 900 RPM for a baseline, keep the adjuster bolt loose for further tuning.
  5. Connect vacuum gauge to intake manifold where brake booster vacuum line normally goes.
  6. With engine warmed up and idling, turn the distributor clockwise and counterclockwise until the maximum vacuum is achieved.  For my car with a stock cam this was 21. This will be lower if you have a performance cam.   If the needle jumps a lot, or you have low vacuum, fix those problems first.
  7. Retard the timing (counterclockwise) until the vacuum is 1.5 to 2.0 lower than the maximum.  For my car this would be 19.5.  Tighten Distributor clamp.
  8. Check timing again with the timing light, distributor vacuum hose disconnected and plugged.  Record results.  Reconnect distributor vacuum hose.
  9. Check balance with Unisyn, adjust as needed.
  10. Check air/fuel mixture with Colortune for both carbs:   one cylinder (1-3) for the front carb, one cylinder (4-6) for the rear carb.  Yellow means you are too rich, or timing is still too retarded. Should be yellow on acceleration, blue at any steady speed.  Red means too lean.  Idle may be slightly yellow.  Record results and settings..  Adjust mixture as needed for the front and rear carb (clockwise richer, counter clockwise leaner).  To start, turn all the way clockwise, counting exactly to the quarter turn how many turns in.  Then turn counter clockwise with the engine at about 1500 RPM until it turns blue.  Turn no more than 3 full turns or the needle will fall out of its carrier and you will have to take it apart.  If you turn 3 full turns counter clockwise and you are still rich timing may still be too retarded. Record new settings.
  11. Verify vacuum is still within the range of maximum – 1.5 to 2.0.
    1. If yes, proceed to next step
    2. If no, repeat steps 6-10
  12.  Remove Colortune and Vacuum Gauge.   Test drive.  Car should ping very slightly under light acceleration, not at all under heavy acceleration.  Keep adjusting wheel on distributor until this is the case.
  13. Check air/fuel mixture again with Colortune.  Adjust as needed, record new settings.
  14.  Test drive again if you had to change carb settings.  Car should ping very slightly under light acceleration, not at all under heavy acceleration.  Keep adjusting wheel on distributor until this is the case.
  15. Repeat steps 11-14 until the engine pings very slightly upon acceleration, and the Colortune verifies the mixture is correct, and the vacuum level is maximum – 1.5 to 2.0.
  16. Using the timing light, observe and record the optimal timing for your car.
  17. Set the adjustment wheel on the distributor to the middle of its adjustment range.
  18. Loosen the distributor clamp, and using the timing light set the timing to the optimal timing for your car as recorded in step 16.  Now you can advance and retard equally from the optimum timing setting.
  19. Verify that nothing “slipped” one more time with Colortune that the mixture is correct (blue), with the vacuum gauge (max – 1.5 to 2.0 at idle), and a test drive that pings slighty with mild acceleration, not at all with heavy acceleration.
  20. Record all the appropriate settings:  max vacuum, vacuum when timing is proper, timing, air mixture (turns from fully closed), octane, colortune notes.

5 thoughts on “How to Fine Tune Timing on a Triumph TR6

    • no sorry. But if you ask someone in your local triumph club, or ping one of the forums like the british car forum or the triumph experience, there may be someone local to you.

    • Hi Yannick, thanks for commenting. After I did this, I had my distributor rebuilt by Advance Distributors, who used a Lucas as a core. They recommended 15-17 degrees BTDC. I set it at 16, and have not played with the vacuum since. I do not remember exactly what it was set to before, but it was a little more advance than the manual specified setting, by a couple of degrees.

      • Bruce Thanks, I found your vacuum method well explained and used too for my TR6 and always end up around 16 to 17 BTDC but I get my distributor rebuild to at distributor doctor UK who set the exact advance to match your camshaft if out of standard Thanks again for your explanation and reply, good ride.

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