and do i need one ? octane around here only gets up around 91 . My car has a 350 .30 over , aluminum heads ( 64cc) pro-flo fuelinjection.
Thanks,
Gary

Only if you need it. That depends on not only how the engine is built, but how it is adjusted, and driven. Octane boosters can improve performance and fuel mileage. They can also hurt both. Too much is as bad as too little.

It won't hurt you to try it once and see what happens. Most of the time they are a waste of money if you use good fuel. Sometimes they are worth their weight in gold.

Be sure to check and see if the one you choose has lead in it. Lead will kill Oxygen sensors (81 and up) and catalyic converters (75 and up). That gets expensive.

|UPDATED|4/21/2004 8:31:26 AM (AZT)|/UPDATED|

Thanks,
The reason I asked was sometimes when I stomp on the accelerator it kind of pings/rattles. So it could just be timing or something or the fact it has only been driven 500 miles in the past 2 years by the guy I bought it from. Gas probably isn't the best after that much time either I guess.
gary

no, and you have bad gas

Check your timing and see where it is set. If it is advanced too much it will cause your engine to ping. If you are running higher than 10 to 1 compression, you might have to run high octance gas or look into octane boosters. I run C 5 Octane Booster in my car. It is made by VP Racing and can be found at certain speed shops. This allows me to advance my timing where I want it without the ping. I have tried many of the other products carried by the parts houses and retail stores. They work a little, but always foul the spark plugs.

______________
sstanford '76 L48

Thanks for the replies ! I hope to have her cleaned up and some nice weather this weekend to empty the tank and blow out the cobwebs !

Be careful!!! Octane boosters that advertise their octane boost in points, mean that they will boost your octane by 10th's, not full points. If it says it will boost your octane by 7 points then it will increase by 0.7 not 7.0 . So if your running 91 octane you will only end up with 91.7 octane and a hole in your wallet.
I have been using toluene for octane boost with no problems so far. I mix about 5-10% toluene per tank. With 91 octane I end up with about 96-98 octane.

______________

NOTHIN' BETTER THAN THE RUMBLE OF POWER WITH THE TOPS OFF AND THE SMELL OF BURNT RUBBER!!|COLOR=SILVER| |/COLOR|

Trevor,
What is toluene ?

|UPDATED|4/26/2004 5:29:14 AM (AZT)|/UPDATED|

After a fair amount of time researching octane boosters I can tell you that from what I've learned, they only coat your combustion chamber to prevent detonation and they do nothing to actually boost octane. There is no substitute for high octane fuel. Try mixing 110 octane race fuel with premium and you will see for yourself.

This is based on personal experience with 11:1 compression and a 3/4 race cam in a '69 350/350.

Best of luck!


______________

'69 350/350 conv.

R1stVette said: Thanks, The reason I asked was sometimes when I stomp on the accelerator it kind of pings/rattles. So it could just be timing or something or the fact it has only been driven 500 miles in the past 2 years by the guy I bought it from. Gas probably isn't the best after that much time either I guess. gary

before you go looking for octane booster which just treats the symptom.. you need to look at the causes.

you need to do a thorough tune up on this vehicle.. that means replace the rotor and cap... REPLACE the rotor springs.. no body ever does this and it is one of the most common causes of timing problems on old cars.

replace the plugs.. and if the wires look or feel cheap, chunk em. it would also help if you could tell us what the timing setting is now..

a car that has only been driven 500 miles in two years sounds like it has what i like to call hibernation sickness.

there is another thread here where myself and ken and a few others discuss "steam cleaning" the engine by trickling water in the carb.. these are all important elements of a tune up when you get a vehicle from someone else... in addition to the standard filters and fluids.

just my $.02 but I would definitely go over all of this stuff regardless of what the last owner said he did..

I have bought cars with "fresh" tune-ups only to find point dwell wildly wrong, plug gap wildly wrong, vacuum leaks, worn rotors with a new cap, etc.

definitely drain your gas and use it in your lawnmower or something if you cant let 2$/gal go to waste. and use injector cleaner when you fill back up.

Ben is right. Look for the cause. The octane booster is just a poor bandage. Cleaning the carbon out is a good place to start, reference the steam cleaning.
You will be much happier fixing the problem instead of doctoring it forever.

Ping knock is a result of too high of a combustion chamber temp. It occours over 2500 deg F. It also creates NOX, more harmfull than CO. There can also be hot spots in the cylinders that cause fuel to light in the wrong place, and makes the flame front from the plug collide with the flame from the hot spot.

These can be caused by carbon, timing, improper EGR (The whole purpose of on EGR is to stop this but can make it worse in some conditions), and high temp in general. If the thermostat is operating too high, the fan is not moving enough air, etc, the engine will run hot and ping.

Ocatane is actually the resistance to burning. High octane fuel burns colder and slower than low octane. The cooler burn drops the cylinder temp.
But the slower, longer burn produces more heat. Don't confuse heat temp with volume. Higher temp does not necessarly produce more heat.

Try heating you house with a cutting torch, very high temp but not enough heat, won't happen. Try cutting steel with your furnace, a lot of heat but not enough temp, won't happen.

The greater quanity of heat warms the air in the cylinder more.

When the spark stops, and the fuel and oxygen are consumed the cylinder is only about 20 to 25 degrees after top dead center. At this point there is no more compustion pressure. So what pushes the piston down?

Not only did we put fuel and oxygen in the cylinder, there is a lot of air. Only 21% is O2. The other 79% has been super heated from the heat of combustion. The super heated air expandes and pushes the piston down.

By high octane burning for a longer period of time it super heats the air more, causing more expansion, causing more power. Heat is your friend, temp is not necessarly good.

Some engines won't run on high octane. The burn is too cold to completely light the fuel. They need the higher temp to do this. Many, not all, new computer cars at this way. High octane will make these cars run worse.

Long answer to a short question.

Look for the cause. Is something worn, set wrong, dirty, or is the engine built that way?

|UPDATED|5/28/2004 7:10:50 AM (AZT)|/UPDATED|

thanks for the detailed explanation ken..

one question I have on this subject that isnt really vette related..

I had an 88 t-bird turbo coupe (which was overall the best car I ever owned)...

it had a fuel octane switch on the dash... for 87 or 92

what exactly did this switch change...

ie did it just advance the timing or something more complex??

It was mostly a timing adjustment. But because the timing affects idle and emissions, the idle and fuel control was varied slightly. Selecting the lower octane did cut power, but should have helped fuel mileage, but only a very small amount. The biggest advantage was spending less on gas. The higher octane selection did make it run better.

Many computer cars, have a knock sensor. When knock is detected the computer retards the timing 2 degrees. If it still knocks, 2 more degrees retarted. When it quits knocking, it advanced 1 degree. Still no knock another 1 degree advance. Some of the newest ones have two knock sensors, and can retard timing per cylinder knocking, instead of all of them. When they have knock sensors they do not need the switch. But many of these use low octane normally, and often high octane won't help them.

The new Vette and several high end new ones have dual knock sensors, run on high octane, but can run low octane and adjust automatically without the switch.

|UPDATED|5/28/2004 6:15:32 PM (AZT)|/UPDATED|