Triumph Repair: 1977 Spitfire Distributor and Timing, haynes manual, correct distributor

Question
QUESTION:   I have a 1977 Spitfire that I bought used and in really great condition. Just a quick rundown. It has the 1500 engine but has been converted to the Weber carb and manifold kit. The engine runs great but I want to make sure the timing is right.
 Now for the question. I am unsure if the distributor is original because the sticker under the hood has the timing to be set to 10 degrees BTDC but the manual states that the  timing should be set to 2 degrees ATDC.  The distributor has  a large block where the vacuum advance diaphragm is and it does not have points but a wheel under the rotor button. I believe this to be the electronic distributor which the manual says to set with a timing light, vacuum advance hooked up, to 2 degrees ATDC.  This is where the hood sticker and the manual disagree.
  Can you give me advice on the correct distributor and the correct timing for this engine?
Thanks
Mark

ANSWER: Mark,

You have the Lucas 45D4E distributor with the "Opus" electronic ignition module.

Which manual are you using?  The best source for timing the later Spitfires is the Bentley manual for the late 1500 (1975-1980).


Cheers,

Jim

---------- FOLLOW-UP ----------

QUESTION: Thanks Jim,
 I thought that it was a 45D4E but just wanted to make sure.  I am using the Haynes manual and Spitfire Owners Workshop Manual I ordered from England.  But say to set the timing to 2 degreed ATDC which is what I have but the hood sticker says 10 degreed BTDC.  It must be a replacement hood.  Last question...why would the different distributors cause the timing to be different on the same engine. Just wondering.
Thanks again,
Mark

Answer
Mark,

Keep in mind that during the '70s Triumph was constantly struggling to meet federal emissions rules.  

There's a good table to illustrate the changes in settings at http://www.triumphspitfire.com/Tuning.html which shows the changes that occurred.

One change that did happened is that instead of the traditional "vacuum advance" some cars were equipped with distributors that were set to vacuum retard... or had setups to both advance and retard based on rpm and vacuum.

For most of the distributors maximum mechanical advance is reached somewhere in the neighborhood of 2000 rpm.  Below that speed you're juggling carb mixture and timing settings to keep the car running acceptably.

Cheers,

Jim