In the years of studying these cars I have learned something: power comes with a cost. Not just the obvious price of upgrade parts but gas mileage and long term reliability. Getting more power boils down to three things… 1. getting air into and out of the engine faster and 2. cutting down on the weight (both inside the engine and the car itself, it takes energy to move weight). 3. and improving the “bang” (higher compression, ignition, etc.).
There are very few “bolt on” items that don’t need other items to work best. For example, if you bolt on a larger carb like a Weber, the car will not have much of an improvement without a low-restriction exhaust system. Yes, you can open the air flow INTO the engine, but you have to give it a way to get OUT better or it negates the flow.
Here is where it starts getting complicated. If you do put on a header, the Weber will need to be adjusted to keep the mixture of gas/air optimal. You are now have much more air running through the engine with the same amount of fuel. You will need to increase the fuel or the mixture will be too lean.
Keeping this in mind, bolt-on items like K&N air filters, larger valved heads, a cam, etc. only help with air flow into/out of the engine.
What readers/surfers have done to increase the power of their Spitfire 1/1-3/14 QuikQuiz
17% Engine Swap
8% Hot Cam
6% High Compression Pistons
6% Electronic Ignition/Hot Coil
4% K&N Air Filter
4% Other (Added Overdrive, Supercharger, Disconnected Intake Manifold Heating)
3% Tune Up
3% Mill (skim) the heads to increase compression
1% Electric Fan
Headers/Exhaust allow “air” to move out of the engine faster.
Carbs allow air to move into the engine faster
Engine Swaps: going to larger engines that already have more horsepower
Hot cams help the valves bring in and expell more air
High compression pistons increase the size of the “bang”
Electronic Ignition/Hot Coils help the spark (that causes the bang) happen more cleanly and larger
K&N Air Filter allow air to move into of the engine faster.
Other (Added Overdrive, Supercharger, Disconnected Intake Manifold Heating)
Tune Up helps the engine do what it is supposed to do, how it was designed to do it
Mill (skim) the heads to increase compression
Electric Fan reduces the load that the belt driven fan creates on the engine
Headers & Exhaust Information related to headers and exhaust systems
Carbs Stories about engine swaps and upgrades in reader’s cars
Engine Swaps Stories about engine swaps and upgrades in reader’s cars
Electronic Ignitions Items I have found about ignition systems
Tune-up Data It is amazing how much better you car will perform when running at peak tune
Head Info Information about Spitfire heads and swapping between 1300 and 1500cc engines
Building a reliable Spitfire engine for Performance The title says it all.