65hihp

I know the topic has no doubt been covered, probably many times.
But I am a newbie, with my "new" 1965 327/365 hp roadster. My car is running original drive train, with its 11.0:1 compression ratio, and I assume original valve seats. There is a dealer near me that sells 111, 113 or 118 octane leaded fuel, so I can obtain this with no trouble, and I can safely store small quantites of it.
What is the concensus of opinion regarding the value or detriment of mixing in a dose of this when I fill up, with normal 91 grade unleaded gas. Is there any down side for my engine? I am willing to accept the extra cost of the racing gas, and mild inconvenience of getting it, considering the car is a Sunday driver.
Thanking all in advance for your advice.

rayvaflav

I recently (last fall) filled the tank on my '66 300hp with 103 octane from a local Shell station really expecting a boost. I guess with the temperature in the air a little lower and a little more dense I was probably benefitting from that more than the higher octane. I will try it again in the summer and will be expecting a difference. One thing that I did notice were the headaches (seriously, not a pain in the *** but an actual pain in my head) from the higher octane fuel. I mean, all I had to do was get near the car and I could feel it. Starting the car in the garage with the side exhuast (yes, the door was open) was a real nightmare. But hey, I'll do it again in a couple of months !

wmf62

my FI car ran great when i added about 20% unleaded racing fuel (and not worth a darn without it..); but for as many miles as i drive, i couldn't afford it....
Bill

MikeM

I think you need to forget about it. You're wasting your time/money if you have an engine built to stock specs.

My 327/360 hp engine runs fine on 89 octane. If I wanted to keep my foot in it, I'd use pump 93 which I know you don't have but yours should run fine on the 91 which I think you have.

steve58

will only run right with 110 in it, whether mixed or straight, but I think on a stock engine you probably don't need it. Best to do is run a tank without it and then with and decide if there is a difference.

steve

62Jeff

If I remember correctly (standard "I may be an idiot" disclaimer) octane is a measure of a fuel's ability to resist spontaneous ignition resulting from high temps and cylinder pressures.

Running a really high octane fuel just means that your car may have to work harder to get the fuel mixture to ignite - in other words you could see a performance decrease.

My 62 327/340 horse car only runs without pinging if I mix 93 octane and other additives, but I've been told that's because I'm a moron who can't tune a car and has no business being seen driving it. In reality it seems I must have other issues (with the car) than I've discovered yet.

Your experience may be different.

435er

Most of our corvettes with high compression engines will run on pump
premium as stated.However there are some cirumstances where Aviation or race fuel may cure an ill,such as perculation or significant pinging or detonation.This is not a fix but more than likley a masking
of a tuning spec.concern which has been explained.In some cases this
works,and very well i might add.Hands up i am a Lepper,in my case the
car is not driven much but runs excellent on 100 octain unleaded available at the pump not far from home.I am not condoning this method
however it works for me.Do not post many threads,just felt like responding on this one.Great Forum with good guys on board.
435er

Mike Ward

Your statement is correct (about resisting spontaneous ignition ).

If an engine does not 'ping' on a given grade of fuel, raising the octane rating will not yield any benefits whatsoever other than possibly helping with percolation issues.

The myth that 'racing gas' will generate more power just won't die.

Tintin

I was once sponsored in Canadian pro racing by Texaco-Havoline and their opinion was that it was better to boost low octane and thus get high heat fuel that didn't ping rather than to use high octane. It only matters that the car does not ping, after that you are wasting money..

If you use leaded fuel in L.A. in a road car and get caught (and it isn't that hard to get caught, have you smelled 110 exhaust?) you will lose a ton of money, possibly your freedom and maybe your car. There are some nasty Federal laws and of course the CARB/California EPA laws that will really be unpleasant.. It is a super big health hazzard as well, try not to get any on you...

65hihp

To all who took time to answer my query,,,,,,,
thanks for the input.
I think I will ditch the idea of mixing in racing leaded fuel.
Three cheers for the corvette forum!

Jims66

For what it's worth....., I have a stock '66 L79 with the following differences...... Bigger valves (2.02 I / ??? E) in the stock iron heads and a Holley 750cfm vacume secondary carb vice the stock 600. The car has a 4 speed and 336:1 gears. I've never had a problem with 93 octane unleaded pump gas since I had the motor rebuilt in 1989-90 timeframe. The only gas related issues I've had was last summer with I think might have been caused by Ethanol at the pumps....... It leaned out a tad which made it backfire "twice" which blew the power valve. I replaced the power valve (and accelerator pump too because I had one in the drawer anyway) then richened the idle mixture a little. I left the jets the same (#70s). Plugs burning clean and no stumbling or pinging. So far so good.

GDD

You need to keep in mind that where you live the outside temp can reach 95+ all summer long. For your car adding leaded fuel will probably not make a difference but for a Fuelie it can make all the difference in the world. I run approximately 1 gallon of leaded racing fuel to 2.5 gallons of pump 91 and my fuelie runs cooler and more tollerant of the hot weather.

ErminewhiteC2

In our part of the country--Wisconsin--the Kwik Trip stations have NO ethenol in the premium grade gas. They are marketing it for recreational vehicles and boats. My 2-stroke 4-wheelers and chainsaws sure run better on it. Although some of it might just be the higher octane.

clarkakirby

I own a '65 with the L76(327/365) engine option. It runs fine on unleaded premium (93 octane). My engine is tuned to factory specs and has the Pertronix ignition conversion. When I first bought it, I was scared into adding octane booster and lead substitute, all later found to be snake oil. I have since put 4,000 miles on the car in ten months. -Clark

Mike Ward

The other day I stood and watched a guy fill his Tercelish econobox with 93 octane- having no choice but to do so as this was the only high octane pump at that particular station- and he got there first. He then pulled two 5 gal jerry cans out of the trunk and filled those with 93 also, ostensibly for his yard toys.

Fearing the worst, I couldn't help but ask why he was using 93 instead of 87 and got the usual babel of 'starts better, runs smoother, idles better, gets better mileage, runs cooler, cleans the engine better', basically every myth we've been hearing for decades.

For the very first time in my life, I resisted the temptation to help the guy out and to save some money. I just said 'that's nice' and smiled. I must be getting mellow. Or have just given up.

Formula Outlaw

A few years ago I filled up with 115 octane race fuel in my then stock 65 L-76. Ran like crap. Was later told that the higher the octane, the slower the gas actually burns, and that all of the gas was not burning. (Hmmm, maybe that was the wierd smell???...).

After running about ten gallons out of it, I refilled with the pump 93 and it ran better, ran that through it, refilled with pump 93 and the car was back to normal.

I, like many others, thought, the higher the octane the more horsepower, but it doesn't work that way...

wmf62

by my recollection, the slower burning high octane fuel allows the timing to be bumped up (fast uncontrolled burning is the source of spark knock...) and therefore bumping the timing up can increase HP and performance...
Bill

yesfam

But it's for racin', how can it not be true

Donny Brass

tune for racing gas, and it will help you make more power, put it in your stock vehicle at factory recommended settings, and you just get better smelling exhaust......

mrruffhouser

First, let me say, There is no such thing as storing gasoline safely at your home. I see that you list LA as home. I'd hate to think of your liabitity if that stored gasoline went up. We wouldn't hear from you for a long time.
Secondly, you can only take short drives if you use hi-octang gas that you can't buy at normal gas stations. Please don't think of carrying around a jerry can of gas in you trunk, especially in LA.

Swap out those heads for lower compression and you will be able to drive anywere on pump gas. Cheers.