What are the best simple mods for HP boost?

[MIGHTY 8]

Mark, have you ever weighed a factory drive shaft assembly?

Are you referring to the weight of the drive shaft itself?
Have always wondered if it's worth the trouble for someone (MM) to fabricate "lightened" versions

[FiatMac]

au contraire, my 500 picked up 9hp upon installing the lightweight flywheel. Dyno comparisons were done before and after the swap

Actually, a lightweight flywheel will not add horsepower--it only frees up horsepower while you are accelerating(less horsepower is needed to accelerate the flywheel and is therefore seen at the wheel). Mark, I am guessing that the dyno you used was an inertial dyno which is always accelerating. If this had been on a load bearing dyno where the load is held at each speed (no acceleration at each point), no horsepower gain would be there.

However, that horsepower that is freed up during acceleration is a real performance gain as it allows for faster acceleration.

[RRoller123]

parasitic loss.

[bradartigue]

Things that will absolutely increase performance that you can do without pulling out the motor:

- Buy a Weber 34ADF Carburetor

- Use a Marelli electronic ignition or one of the aftermarket electronic types. Use the Marelli only if your carb has a vacuum fitting for it, or if you are brave enough to drill one yourself (not hard).

- Get rid of the catalytic converter. If you feel bad about this then know that your car can pass emissions without it, FIATs actually burn pretty clean when properly tuned

Increase performance by just pulling out the head and refitting it:

- Simply replacing the old valves, having the head cleaned and surfaced, and installing new valve seals, gaskets, etc.
- Mild performance cams
- Hotter cams and adjustable flywheels
- Larger valves
- Polishing of the chambers and ports

And then we can go on and on and on. You have some guys here with $8k engines and they love them, and some guys with $2k engines and they love them. Start with simple stuff, the carburetor is easy to replace, so is the ignition.