Triumph Repair: Carb adjustment, best gas mileage, overdrive transmission

Question
QUESTION: Hi Jim,
  I bought a 1977 Spitfire and I am trying to get everything tuned to the best possible fuel and power settings.  The engine supposedly has 95,000 miles on it so it's not new.  It came with the Weber 32/36 DGEV carb and intake kit, some type of 4 in 1 exhaust header and I guess everything else is stock. I am getting a black soot on the back bumper after long drives and the exhaust smells rich to me.  Also when I run it at higher rpm's and then let the engine decelerate quickly it will smoke grey/white smoke for a while.  When tuning the carb I used a Colortune and on the 3000 rpm test it would not stabilize to blue but would run orange/blue.  The idle circuit adjusts out fine. The main jets are 140 or 1.40mm.  I am also still playing with the timing to get the correct setting.  One place I reads says 10 BTDC with no vacuum and another says 2 ATDC with no vacuum set with a timing light.  Can you help get me started tuning this engine correctly? I drive this long distances and need the best gas mileage.
Thanks,
Mark

ANSWER: Mark,

Gray/white smoke on the overrun is a lean condition.  Black soot on the bumper is either the idle jets too rich or the accelator pump pushing too much gas.

As to timing setting, which distributor, and what else is still hooked up emissions wise?

And what kind of gas mileage are you getting now?  Keep in mind that the Spitfire is a small car but it wasn't built to purely be a gas sipper.  

If you're serious about gas mileage you want either an overdrive transmission or to do a conversion to an aftermarket 5 speed setup.


Cheers,

Jim

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

QUESTION: Okay now were going in the right direction.  The tail pipe is black sooty as well.  The idle adjustment was set using the colortune and it is correct.

The distributor is a Lucas 45D4E distributor with the "Opus" electronic ignition module.  There are no emissions hooked up.

The spark plugs look good after a hard run.  The insulator is a tan color. The color change on the electrode is in the bend center but there is a black soot on the base threads.

As for the mileage, I get about 30 mpg which is good for me.  I would like to add an overdrive tranny soon to squeeze a bit more out of it.

But for now my biggest concern is just making sure the engine is tuned correctly.
Thanks again

Answer
Mark,

One thing I wonder is if the engine was ever rebuilt... if so it could have the high compression pistons.. or it could have had them from the factory as British Leyland was a bit quirky towards the end.

If it's not a "California" car then 10 BTDC (vacuum lines plugged) or 14 (+/-2) BTDC at 1100 rpm is the recommended timing.  One thing to try is to advance the timing gradually until you hear it pinging... then you're advanced as far as the engine will stand and should get about the best mileage possible.


Cheers,

Jim