This is the same as any car you might modify, you start off by deciding how far you want to go, what the car will be used for and how much money you can afford to spend. The following recommendations are given without guarantee or warranty and must be carried out by a competent mechanic or experienced DIYer. The guide is designed to give you the maximum enjoyment out of your car while keeping it safe and reliable. It is aimed at producing a track-ready car which should prove durable. The cost of modification is greatly reduced by your ability and time willing to spend working on the car as well as having a dependable and reasonable local garage to tackle larger jobs or technically more proficient jobs like welding and braising. Remember you don't get anything for nothing.
You generaly have two routes you can go. You can either use the original X19 engine which can give up to 140-150 hp or you can opt for the Turbo route by using a Fiat Uno Turbo engine, power can easily be increase to 150hp and up to 190hp. Dependant on the availability of the Uno Turbo in your country the cost can vary, but generally the fitting of the Uno engine is cheaper than a fully worked X19 engine to obtain the same power results. The following modifications are split up by budget.
Low budget $500
Change the air filter box and replace with a K&N, ensure you fit ducting from one of the side air scoops, some for of heating ducting can be used for a cheap alternative to expensive motor sport stuff.
Re-jet the carb - trying going up 2 sizes on the main jets and air correctors, you can remove these without removing the carb and can be done while testing on the road. To access them remove the air filter and the jet sit between the inlet chokes. Tip - If you don't have long nose pliers that fit try using a MacDonalds Straw (the only good thing they produce and exactly the right size for weber jets) with the ends cut in a cross shape. This way it will slide over the jet and grip it.
Ignition - Change the coil and plugs for some performance ones, this will help produce a strong spark creating a full and healthy burn. Change the ignition to an electronic type, this will ensure things remain crisp at higher revs.
Change the exhaust rear box for a CSC system, very competatively priced at 80 pounds or $135 online at gazzello racing in the uk.
Results - Power increase by 15hp from 85hp to about 100hp with more power higher up and a greater ability to rev. Brakes will cope with as much as you can throw at them. A much faster car.
Medium Budget $1500
Change to Uno Turbo discs and calipers with performance brake pads
Increase tyre size to 185 section
To keep within the budget you will be looking for secondhand alloys and you don't want to go bigger than 185 section tyres. If you want to retain 13" wheels the Lancia Montecarlo phase 1 alloys look very good and are 5.5" wide or even Uno Turbo phase 1 alloys will suit. Most other options will involve going for 14" alloys where a range from Croma Turbo to Strada Abarth will fit. Dependant on which model they come from you may need to use spacers to attain the correct offset.
As above exept
Change the exhaust as the standard exhaust is totally inadequate and restrictive. CSC do a performance manifold and system for about 200 pounds or $350 plus shipping. You can get this from gazzello racing in the uk.
Performance cam bought from guy croft or gazzello racing, although this is stretching the budget to the maxium.
Results - Another 15 hp taking power to 115hp, (carbs now totally restricting the power, if these were weber twin downdrafts power would increase by 25hp at least to 125hp)
High Budget - $3000>
New coil springs or Leda coil overs
Uno Turbo with ducting and motorsport pads ferrodo DS2500
Increase in size and rim width to 205 section tyres at least
Flared arches to cover the increased wheels size
N/A engine with Guy Croft Stage3 head, gas flowed, larger valves and very high compression. Tubular manifold and matching system, twin 40 downdraft webers and highlift long duration cam (Kent cam - Scott Development spec). 15 row oil cooler. Electronic ignition. Lightened flywheel and high performance clutch.
Power output should be 155hp. You can takes things further with this engine, dry sump, forged pistons and if you can find it from Italy the Ferraris 16V head. With fuel injection and an engine management system this would put out over 220hp but is extremely expensive and represents the absolute panicle of the engine.
Take one Uno Turbo engine, substitute the cam carrier from the X19 engine and modify the gearbox to accept the flywheel sensor for the uno turbo ignition. Fabricate piping for the intercooler and mount near the side are scoop. Install the wiring loom for the ignition and fuel ECU which are plug in and play only requiring power and an earth. It's that easy to do it the only problem comes with the temptation to raise the boost.
The turbo engine provides 105hp as standard at about .7bar boost. With the addition of an adjustable fuel regulator like an FSE type the fuel pressure can be raised and the boost can also be raised. A 'safe' limit of boost for the Uno engine is 1.1 bar which will give about 150hp although care should be used to edge up to this limit. I have run engines up to 1.5 bar of boost (200hp) which is the limit for the turbo and this has already surpassed the limits for what the standard engine mangement systems can deal with. If you want boost past 1.1 bar and are loooking for big power you should consider an engine management system like MOTEC, a larger turbo and different injectors. Professional set up is required I'm quite sure the engine will take up to 2 bar of boost without changing the standard pistons which would give over 280hp.