Minimum octane for L84?

[Michael G.]

I recently discovered a gas station near my house that has 90 octane ethanol free gasoline. I've been running 110 racing fuel that I have to buy in cans, so using mostly pump gas would save me time and money. Can anyone tell me the minimum octane (at todays rating scale) that my two stock 63 L84's should need to run normally? I can still add some 110 to raise it a bit, if necessary.

Thanks,

[Donald T.]

Re: Minimum octane for L84?

Mike,

Have you tried running straight pump gas? The minimum octane would be the minimum necessary to prevent detonation. If your car runs on pump gas without indication of knocking/pinging, then you don't need more octane. It may run fine on the 90 and unlikely it would require much more unless the compression has been raised. You could also retard the timing a little.

[Stuart F.]

Re: Minimum octane for L84?

I too have found a station near my home (12 miles) that sells the 90 Octane non-ethanol gas. I'm on my first tank now so may have to run it out to purge the old 93 Octane ethanol laced fuel. I do use max lead 2000 in the mix to be safe anyway. I believe the 90 octane non-ethanol may be even more prone to detonation than the gas with ethanol and will require the boost (of some sort) even moreso. Mine runs much better with the good gas, is more responsive, far less stinky as it doesn't evaporate so quickly, and just in general better driveability. It is worth the drive. The station owner said they used to have 92 octane, but he is unable to get that anymore. For me, lowering compresion ratio or reducing my timing is not an option at this time. I like my redline runs too much.Stu Fox

[Michael G.]

Re: Minimum octane for L84?

Hi Don, On trips I've run both cars on mostly 90 octane (I added it to a tank that had about 1/4 tank of racing gas remaining). It always ran fine, no apparent pinging, but I haven't tried straight 90 octane, no alcohol, no lead. The compression on both cars is standard and timing is as recommended for a stock L84, so, I'd guess 90 would be adequate, but just thought someone might have a better feel for it. I'll empty one and re-fill it with 90; I can alway add some 110 or retard it if it pings.

Thanks,

[Doug L.]

Re: Minimum octane for L84?

I think Don has the right answer above. It is my understanding that when '63 / '64 L-84s were new, owners had a lot of complaints about knocking. This was back in the days of 100+ octaine being available at every gas station. As I recall Sunoco had pumps where you could dial the specific octaine you wanted. I read that the dealers during that period added an extra head gasket to give a total of ~.040 thickness, thus reducing the compression ratio. At disassembly I found 2 steel gaskets on each cylinder head, sort of confirming this practice. When I rebuilt my engine I installed 0.040" composition gaskets.

On my way to the gym I noticed a boat yard advertising "non-ethanol" gas. The sign didn't say what the octaine rating is but I will check. Maybe marine engines are affected negatively by ethanol. I know many avialtion piston engines are. Those engines are 50s and 60s technology which has caused high octane leaded fuel to remain available at airports. The initial startup of my engine after re-build was with 100 octaine low-lead aviation fuel. You can't usually get an airport manager to pump it into a car's gas tank so I drained some from the tanks of my plane. At some point I'll try pump gas and if the marina gas is high enough in octaine I'll try that too.
Doug

[Paul J.]

Re: Minimum octane for L84?

Mike, I would first be sure that the fuel actually has no ethanol. I would find out who the oil jobber is and call him. If there are no state or local programs requiring ethanol in your area, he should be able to tell you other stations that have non-ethanol fuels, perhaps in higher grades.

Obviously you can adjust your timing to where it will run fine, but with less performance. All of this is dicsussed in the archives. But it is a moot point if there is a misconception or misunderstanding by the station that they have non-ethanol fuel.

Paul

[Paul J.]

Re: Minimum octane for L84?

On my way to the gym I noticed a boat yard advertising "non-ethanol" gas. The sign didn't say what the octaine rating is but I will check. Maybe marine engines are affected negatively by ethanol. I know many avialtion piston engines are. Those engines are 50s and 60s technology which has caused high octane leaded fuel to remain available at airports.Doug

Doug, ethanol is hydroscopic. It absorbs water, so you will not see it at airports and marinas. It is not used in those applications, but it is "illegal" to put it into a car because there are no road taxes on it. Same with race fuel.

Psul

[Michael G.]

Re: Minimum octane for L84?

Actually, due to our proximity to many lakes, I've found that several gas stations in our area carry 89-90 unleaded, alcohol-free gas for boats, at their normal pumps. These are not restricted for automotive use, as is racing fuel or 100 LL aviation fuel from airports.

I'd rather not handle the racing gas, if possible, that stuff is pretty toxic. If I can get my cars to not ping on standard no-alcohol gas, even with more retardation, I'll try to do it.

[Michael W.]

Re: Minimum octane for L84?

Michael,

Not to start another battle royale, but many of us have been using E10 fuel for decades with absolutely no problems. If the 90 octane no-ethanol doesn't avoid detonation, try higher octane rating irrespective of the ethanol content and see if it cures the problem.

[Dan H.]

Re: Minimum octane for L84?

Michael. I only run 91 Octane pump gas here in Ca. 17000 miles and runs fine, plugs stay perfect also. Did find some non ethanol gas when in Oregon, raised my gas mileage 2 mpg, to about 21 mpg. Timing reads 10 degrees at 900 rpm. FI helps to control ping due to even air fuel ratio throughout all cylinders. If you like to travel, set your car to run on pump gas and forget it!
Dan

[Michael G.]

Re: Minimum octane for L84?

Michael, I'm not suggestng that alcohol causes detonation problems. The issue with alcohol on my cars is not detonation, but vaporization. These are fuelies, so with the slightest bit of alcohol, both cars become hard to start when hot, and the idle, normally about 700 RPM, cycles between 400 and 1400 RPM constantly. With 110 raciing fuel or 100LL (neither has ethanol) this is never a problem, even when very hot.

Thanks,

[Michael W.]

Re: Minimum octane for L84?

Michael, I'm not suggestng that alcohol causes detonation problems. The issue with alcohol on my cars is not detonation, but vaporization. These are fuelies, so with the slightest bit of alcohol, both cars become hard to start when hot, and the idle, normally about 700 RPM, cycles between 400 and 1400 RPM constantly. With 110 raciing fuel or 100LL (neither has ethanol) this is never a problem, even when very hot.

Thanks,

Thanks for the post. It's useful to see first-handed experience relating some pros and cons. There's been considerable discussion on the VH site regarding fuelies and E10. Some of the thinking is that more recent fuels have a higher vapour pressure rating that exacerbates the problem and that the presence of ethanol may or may not be directly related or to blame. There's other evidence that there may be some geographical differences with Florida being the most heavily affected.

[Michael G.]

Re: Minimum octane for L84?

Michael, I don't think its clear to anyone whether the problem is actually the vaporization of the ethanol itself, or, the fact that the gasoline mixture gets reformulated when mixed with the ethanol. It may just be that there is more or less of some other components in the mix, or, that another hydrocarbon (or a few) is added to the mix only when ethanol is present. Either of those possibilities could effect the vaporization of some portion of the mixture.

I just know when Michigan's gasoline/ethanol mix hits my fuel systems, the cars run like crapola; when its not there, they run great. As an interesting sidelight, I once filled up with some "Turbo Blue" 110 ethanol-free racing gas and the car immediately started acting like it had alcohol in it. I woulda bet a bunch of money that I just paid $7.00 a gallon for normal pump gas from a Turbo Blue pump! Buyer beware.

When I switch to the 90 octane ethanol-free mix, I may find that the ethanol itself is not to blame, that perhaps modern mixtures cause vapor problems, even without ethanol. I guess we'll see.

thanks,

[Chuck G.]

Re: Minimum octane for L84?

I moved to Florida about 3 years ago. Brought my 63 FI car with me, and immediately began to have problems with "Florida gas". I never had that problem with ethanol gas in Maryland. I also started to have pinging problems with my 69 BB when I "got on it".

Long story short, I found several stations in my area that now sell non ethanol fuel, and I have started to use it. I live in a maritime area, LOTS of boats, boat yards, etc., etc. Car runs great on the no ethanol fuel. I used to be able to buy 92 octane no ethanol, but now I can just buy the 90 octane.

You "nailed" the issue, and that is the "surging" at idle and the difficulty hot-starting. I hated to stop at a red light, as I had to keep blipping the throttle to keep it running smoothly.

I do not have that problem with non ethanol fuel. Let me also say that the old CAM 2, now called Sunoco race fuel, is available down here, but the price is pushing $8.00 per gallon.

AND, to set your mind at ease, I have bought 100 octane LL AvGas at the local airport several times without problems. They will not pump it into your car, but you can bring your 5 gallon jugs. Cost last time I bought it was about $4.30 per gallon.

The car runs like a scalded dog on AvGas.

Chuck

[Michael G.]

Re: Minimum octane for L84?

Chuck, I used to fill up on AvGas and the cars ran great, but now I don't have an airport close by.