Engine Maintenance and Modification Bradley Artigue

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FIAT 124 Spider Engine Maintenance + Modification 11. Improvements* * Ask yourself if things need improving. Performance is a relative term. You need to define how you want your engine to perform so that it suits your needs. A high performance engine is not necessarily fast and a poorly performing engine is not always slow. Lots of car companies state that their engines are “high performance” just because they produce more than “x” horsepower or “y” torque. But look at what these companies do to produce this power - enormous V6 and V8 engines that barely produce ¾ of a horsepower per inch of engine displacement. These can be 350 and 400 cu. in engines producing less than 300 HP. Alfa Romeo and FIAT were producing 1HP per cubic inch of displacement in the 1960’s. Sure, the engines produced around 100 to 120HP, but which one is higher performance? It's up to you to define performance in terms of what you want your car to do. Performance is relative to your needs. Do you want to build a 200HP Spider? It can be done, with a standard FIAT engine block, cylinder head modifications, high compression pistons, lightened flywheel and connecting rods, supercharging, etc. Guy Croft has been building race-prep FIAT twincam motors from his shop in the United Kingdom for many years. He wrote a book on the subject (which is now quite hard to find) in case you want to do it all yourself, or you can pay upwards of $8,000.00 to get it done right by Guy personally. Alternatively, there are numerous things you can do with a relatively stock FIAT Spider and really improve your driving experience. The interchangeability of parts between model years allows you to use off-the-shelf FIAT parts to truly transform your Spider. The good news is that many Spider parts can be interchanged between engine series or upgraded with new parts. These interchanges can be done to improve things such as acceleration, horsepower, and torque. Parts availability and installation ease are both very good; in other words, you may be able to mix and match parts at a minimal expense and create an improved driving experience. This section deals with some improvements that have been proven to be successful in delivering improved performance and reliability. You should approach performance improvements with some caution. There is a financial trap you can easily fall into, with your improvements quickly reaching the point of diminishing returns. A set of new carburetors, head work, pistons, camshafts seals, rings, and all of the other parts can easily set you back three or four thousand dollars. It is very easy to say “since I’m pulling the motor anyway, I’ll go ahead and install new, high compression pistons and those lightened connecting rods.” Consider that your tired engine may improve dramatically by rebuilding to stock (or near stock). There are exceptions, such as the Spider 2000 fuel system, but for the most part these cars were very nice performers in stock form, and some relatively inexpensive changes may meet all of your needs. 80
FIAT 124 Spider Engine Maintenance + Modification 11.1 Cylinder Head Improvements We’ve discussed how the head works in previous sections. Let’s talk about the things that impede the efficiency of your cylinder head and how to overcome these performance-robbing issues. We will start by discussing some cylinder head nomenclature then working backwards, from the late model smog heads down to the early Spider heads. 11.1.1 Nomenclature You may have heard the expressions “porting,” “polishing,” “matching,” and “blueprinting.” These are all methods of optimizing the airflow through the cylinder head. Keep in mind that the head is the top of a big air pump (the engine) and the more efficiently air can pass through the pump the more performance you will get from the vehicle. A head that is ported, matched, or blueprinted has the port sizes on the intake and exhaust manifolds match those on the cylinder head. In other words, the pipes leading out of the cylinder head and the pipes leading into the head do not reduce or have interference in between. The gasket mating the two engine parts has been cut, if necessary, so that it does not baffle the airflow in between. The ports on the exhaust side are matched as well. FIAT heads typically have no resistance between the ports and the gaskets do not protrude into the airflow. A polished head is one that has had the combustion chambers and ports polished so that nothing in the aluminum may disturb airflow. Polishing to an extreme can be counterproductive as it may eliminate some of the “swirl” that is good for combustion. The good news is that the FIAT heads are usually very smooth and require little or no polishing. 11.1.2 Head Specifics We’ll work backwards from the late model heads to the early types, since the most popular and effective swaps occur more frequently with the late model Spiders. The Spider 2000 fuel injected head is very “clean.” The fuel injection system did not require the myriad of pollution control devices found on the carbureted 2000 head. It is essentially a straight head with good combustion chamber size and shape, and good port sizes. If you are curious about the hoses and pipes all over the top of the head they are all related to the fuel injection system and are not actually interfering with the combustion chambers, ports or valves. Fuel injected heads have the same camshaft profile as every other FIAT Spider. The Spider 2000 carbureted head is an example of what FIAT did to meet EPA regulations. Depending on where your car was sold (California, for example, had different regulations than other states) it may have an EGR bypass that squishes the #1 combustion chamber, reed valves that run into the head and to an air pump, vacuum ports on the intake manifold for various emissions control devices, and, as mentioned earlier, a restrictive exhaust system mated to it. The head, intake, exhaust, and 81
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