Triumph Repair: Spitfire ignition timing, weber dgv, vacuum unit

Question
Hi Jim,
I have a 1980 Triumph Spitfire. (California model)
The car has ALL of it's pollution control devices removed, including catalytic converter, air rail, air pump, PCV valve, etc.

I just removed the ZS carb, and replaced it with a Weber DGV carb.
The instructions with the Weber said to NOT connect the distributor vacuum unit.

My question is: What should the ignition timing be set at. (Since the vacuum retard unit is no longer connected)

Here are the way I see my options, and I would appreciate your opinion on which you feel is correct.

Option 1) Set it at what the under hood decal says.
The decal under the hood says "2 degrees ATDC at 800 RPM (with vacuum unit hooked up)". If my understanding is correct the retard unit ONLY has an effect at idle, and they used the unit to retard the timing, to keep the pollutants at a minimum at idle. (Because at idle is when the testing was done.)
Therefore without the retard unit connected, the timing should be at a more advanced setting.
So this option does not seem correct to me.

Option 2)Set the timing at 10 Degrees BTDC.
This is the setting in the manual for the Spitfire that is sold outside the USA.

Option 3) Set the timing adjustment so that the highest RPM is achieved at idle, then advance 5 degrees.
I have read that this is the best way to set it on an engine that the timing is unknown.

Option 4) Yet another option suggested by Jim.

I personally am leaning toward option #2 (outside the USA setting)
or option #4 (The Jim suggestion)

What do you think?
Your help is greatly appreciated.

Sincerely,
Ed

Answer
Ed,

It's going to be a question of how well the carb is setup.  Hopefully the jets in the DGV are fairly close to what you need in the car long term.

With the vacuum retard disconnected then yes, you're essentially running at the non-California spec for a mid-70s Spitfire.

For any of the cars, for best performance you're looking for between 30 and 35 degrees total advance (BTDC) at full advance (above about 2k rpm).

Keep in mind the original distributor is about 30 years old (assuming it's the original) and the bushings in the distributor may be worn.  Might not be a bad idea to consider one of the aftermarket distributors too.


Cheers,

Jim