Octane and coolant questions...

[excelguru]

1. My car has about 10:1 compression, so I can run 92/93 octane all day long. I filled it with 100 octane and ran it without making any changes (such as timing, etc.). Did I cause any harm to the engine? Flames came from the pipes at WOT (which, I must admit, looked cool as hell - they caught it on video). But the cool video got me to thinking that maybe I was harming something. This occurred at night. The flames are invisible in the daylight.

2. Additionally, should I expect any performance increase from 100 octane since my engine isn't 12:1 or whatever? It seemed stronger, but I could have imagined it.

3. Okay... I open the valve at the bottom of my radiator to drain it. I wait for all the coolant to exit. Then if I remove the temperature sender unit at the top of the engine, I can still see a liquid level right there almost within touching distance inside the block. I can't get it to drain out any more fluid. Is this normal? Is all the coolant really drained? Did I miss a step?

[ToyCollector]

Keith,

You should have done no harm at all. You can always run a notch higher octane. In aviation, we are even taught that if your plane takes 80, and they are out of 80, ask for the next grade up. But obviously never trade down octane ratings.

I run 100 octance in my race car, which is a stock motor, as it actually burns cooler than 93 octane, and results in about 10-20 degrees fahrenheit lower engine temps. That is the #1 reason we run it when we race. (Isn't the smell great ??) If you were to tweak timing, etc, you would have more play without risk of detonation and then maybe more power with the higher octane. Without a change of engine settings, I would not expect any HP gains without an electronic computer, but there are others who likely know more. But as it was, you should have done no harm.

Without seeing the coolant thing, I don't know what to say other than I am sure you would have some pooling in certain horizontal areas within the block of coolant.

[excelguru]

If I use 100 octane, which way would that allow me to adjust the timing? Advance or retard? And how far in either direction? Is there something that I should listen for (or watch for) when adjusting it? Or do I simply have to make an adjustment & take a drive, adjust & drive, adjust & drive, etc. and just use my butt-o-meter to determine power gains/losses.

Glad to hear I caused no harm except to my wallet.

I didn't consider that the coolant could have pooled somewhere (duh). I'll check that.

[dalola]

Higher octane allows you to advance the timing. Just go a couple degrees at a time, and be careful! It's hard to hear detonation in a Cobra, as they are usually pretty loud. Keep an eye on your total timing as well, usually having everything in around 3000 rpm.

Usually, just draining the radiator leaves quite a bit of coolant behind. If you really want to remove all the old coolant, try flushing or vacuuming, via a coolant machine. Also, when refilling, if possible, vent something high up in the coolant path to purge air as the new coolant fills up. Watch the level for a couple heat/cool cycles, as it will usually require topping off.

Now, go drive!
~Dave

[auto10x]

Simply remove the coolant plugs from each side of the bottom of the block to drain "all" the coolant.
auto10x
Bill