Triumph Repair: carb, screw head, spec cars

Question
QUESTION: I own a 74' spitfire, what would be the best carb? Also i am a novice mechanic- i bought the car with the intent to gain mechanical knowledge. What are some problems that may occur when upgrading to a better carb(s). I have absolutely no knowledge in timing. I have cleaned and polished ports, corrected valve clearances, changed all oils. The car sounds great now( i bought the car for 800$ and very pleased with the changes i have made on it costing me nothing and look forward to enhancing performance.) Currently i am on a tight budget but i would appreciate your wisdom on best performance carb(s) and maintenance
issues. btw Is timing maintenance difficult? thank you for your previous answers!!!

ANSWER: Earl,

The stock Stromberg in good condition and properly tuned is capable of decent performance.  The typical problem is that after 30 years they're not typically in good condition.

A simple upgrade is to a 1.5" SU, typically a HS4 although some like the more complex HIF44.

Twin HS2 were used on the Spitfire from 1962 through 1969.  You'd need to find a set from a Mk III as the manifolds are different and the early set will not fit the 1500 head.

European spec cars had twin 1.5" SUs and they're the "popular" upgrade these days.

The ultimage carb is the Weber.  For the Spitfire the sidedraft is a better setup as there do not seem to be any decent manifolds for the downdraft.

As to timing, again the problem with you car will be age.  There are bushings in the distributor tower that do wear with age and when worn they allow the timing to wobble.


Cheers,

Jim



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

QUESTION: 1.When you change carbs do you have to alter timing?2.my tires in the back sway inward- is it the shock or the independent leaf spring? 3. there is a bolt on the bottom of the shock that connects it to the tire assembly this bolt moves freely and there is no sign of the screw head what do i do?

Answer
Earl,

In an perfect world the timing should be independent of the carb used.  In reality the factory timing is based on assumptions of how the carb operates... different fuel and different operating conditions (temperature, altitude, speed) require some tweaks to the timing.  

Pick a lightly travelled road and run it several times.  Then try tweaking the timing a bit and see how it runs.  Eventually you should feel performance fall off or hear pinging.. you're too far advanced.  

Are you saying the tires sway inward while driving or the tires are "leaning" when the car is at rest?  With a swing axle car the wheels have a tendency to acquire negative camber (tops inward) as the rear leaf spring sags.  

The rear shock on the Spitfire is mounted on a welded post on the vertical link with a washer/nut combo to hold it in place.  It's possible the stud has broken loose of the vertical link.  If so, it requires immediate attention.