You would never think of taking...
You would never think of taking a hammer to your engine's pistons, but during detonation, pressure spikes are acting in the same manner.
The demon of engine knock is something an owner of a traditional high-performance Pontiac knows all too well. An engine designed when 102-octane high test was at almost every fuel station in the country being forced to run on today's gas means that ping has become an all too common companion, and what if your engine was rebuilt by a previous owner? You may not even know the compression ratio. If octane boost or race gas is not in the budget, the typical frustrated hobbyist's response is a twist of the distributor to retard the ignition timing.
With today's pump-gasoline prices, the thought of filling up a big Pontiac fuel tank is enough to wreck the budget, even without the expense of high-octane supplements. The problem with retarding the ignition timing to eliminate detonation is power, throttle response, and fuel economy also go away with the knock. Less ignition lead, though necessary in some circumstances, isn't the cure for every engine with an appetite for octane--Pontiac, corporate, what have you.
Engines such as GM's TPI are...
Engines such as GM's TPI are prone to detonation due to the heating of the charge air as it travels through the long runner intake manifold.
When fighting ping, retarding the timing should be the last resort, not the first approach. There are, of course, instances when even retarding the ignition timing and adding octane doesn't eradicate pinging. This is not often the case with a properly built, tuned, and maintained Pontiac engine unless you're trying to run a very high compression ratio on the street. It proves there is more going on to create detonation than just fuel quality and ignition lead. The battle must be fought systematically as opposed to randomly.
What is Octane?
Tuning a Pontiac engine begins with an understanding of gas octane ratings. The calibration of the fuel and ignition system should be set for the octane level of the car. Thus, if you want to burn 87-octane fuel, the tune-up is calculated for that grade of gasoline.
By definition, octane is a fuel's ability to resist auto ignition from pressure and heat. Thus, the fuel doesn't ignite, instead waiting for the arcing of the spark plug. The higher the octane rating of the gasoline, the more pressure and heat it can withstand before self-igniting. Conversely, lower octane fuel ignites independently of the arcing of the spark plug through either pressure or heat or a combination.
Coolant flow is critical to...
Coolant flow is critical to controlling cylinder head-metal surface temperatures. This radiator core is an example of what happens when someone doesn't believe in routine antifreeze service. The plugged tubes could cause detonation.
The chemical isooctane is considered a hydrocarbon 2, 2, 4 (a trimethylpentane), which has eight carbon atoms. It's used as a primary reference fuel with an assigned octane rating of 100 for both RON and MON, and n-heptane has an assigned value of zero. The octane number of a fuel is the percentage of isooctane in a blend with n-heptane that gives the same knock intensity as the fuel when evaluated under test conditions in a standard engine. Oil companies use what is called a CFR (Cooperative Fuel Research) engine to determine octane. It's a single-cylinder, overhead valve, variable compression-ratio engine designed for the purpose of testing gasoline.
During the past few years, the octane rating of street gasoline that is posted on the pump is an average of the RON and MON. That is why you see the octane listed as R+M/2. Many years back, there was only one octane rating on the pump, and it was not an average of the two test methods.
RON stands for Research Octane Number and measures the antiknock quality of a gasoline as determined by the ASTM D 2699 method (ASTM stands for the American Society of Test Methods). It is a reference to the antiknock performance of a fuel when the vehicle is operated under mild conditions such as low speeds and light loads.