65tripleblack

It could very well have been. I might have been returning from the beach, or one of the beachfront "watering holes".
Weather permitting, I'll be at Brick Township Summer Fest this Thursday from 5PM to 9PM at Windward Beach. Hosted by Time Capsule Cruisers.
Hope to see you there. I'll be looking for you. If you see me, please introduce yourself.

http://www.twp.brick.nj.us/summerfest-2015

To those who are misinformed and not necessarily BD104X: Lower octane fuel doesn't burn slower, but it ignites later, producing the same net effect and therefore the confusion and myth. It burns at the same rate as higher octane fuel, and it has the same energy density (specific energy) as higher octane fuel. As stated previously, alcohol content WILL lower gasoline's energy density.

ElHombre

Does the 93 octane in your area have a high methanol content?
That could cause some pre ignition issues, as well as attracting water in the tank if the car is not driven often.

BD104X

[QUOTE=65tripleblack;1590140408]It could very well have been. I might have been returning from the beach, or one of the beachfront "watering holes".
Weather permitting, I'll be at Brick Township Summer Fest this Thursday from 5PM to 9PM at Windward Beach. Hosted by Time Capsule Cruisers.
Hope to see you there. I'll be looking for you. If you see me, please introduce yourself.

http://www.twp.brick.nj.us/summerfest-2015
LOL, you don't remember? How many silver C2 convertibles waved to you at intersections that day??? Just kidding - maybe I'll see you in Brick if I can talk my wife out of going to see Pt. Pleasant fireworks on Thursday.

Westlotorn

Was 93 in the car when purchased? It may have been a year old or more.
Fuel Degrades when parked for more than 3 months.

phil2302

You make a good point however we arent sure what was in the tank when we test drove it but within days of getting the car into his shop the tank was drained, cleaned and filled with 93. Plus all the obvious things you would want to do to optimize performance were done. 3-4 tanks of 93 were used up before he switched to 87.
It is weird. I run my car on the same Mobil 93 all the time and it runs terrific.

MikeM

Put some 87 in that plug of yours and see if it'll tear the tires off with that stuff in there.

427435

Thanks.

Here is the write-up.




Flame Speed, Octane Number & Horsepower
Faster Flame Speed Is Always Better For Maximizing Horsepower

There is a lot of misunderstanding about the relationship between flame speed, octane number, and horsepower. There are some connections between these items, but not as many as some people think.

FLAME (burn) SPEED:

THe speed at which the air fuel mixture in a combustion chamber is consumed becomes critical in a racing engine. At 6000 RPM, each spark plug fires 50 times per second. That's a lot of combustion processes happening in a very short time in the same combustion chamber. This is why racing gasoline need to be capable of burning fast. In your daily driver that may not see the top side of 3000 RPM, flame speed is not as critical. In a racing engine, everything is happening much faster, and in a bigger way because the throttle is wide open. The gasoline must burn as completely as possible to make the most possible horsepower. If the gasoline does not get burned in the time allowed, there will be unburned hydrocarbons coming out the exhaust pipe. Besides not making any horsepower for you, the unburned product contributed to air pollution. Flame speed is determined by the hydrocarbon components in the gasoline. It is critical to making max power, but not related to octane quality.

OCTANE NUMBER:

The octane number of a gasoline has little to do with how fast it burns or how much power the engine will make. Octane number is the resistance to detonation. If the octane number is high enough to prevent detonation, there is no need to use a higher octane gasoline since the engine will not make any additional power. Octane number is not related to flame (burn) speed either. Variations in octane quality are independent of flame speed. There are some high octane gasolines in the marketplace with fast flame speeds and some with slow flame speeds. It depends on how they are put together. We prefer fast flame speeds because we know that a properly tuned engine will make more power on this type of gasoline than one that has a slower flame speed.

POWER:

The ultimate goal in the racing gasoline business is to convert chemical energy from the gasoline hydrocarbons into mechanical energy or horsepower. The most efficient way to convert the gasoline into horsepower is to have the correct air-fuel ratio and the correct spark timing. A mixture that is too rich or too lean will not make maximum horsepower. The same is true of spark timing: to much or too little will compromise engine output.

OVERVIEW:

As indicated above, flame speed and octane number both impact the amount of power that an engine will develop, but they are independent of each other. To get maximum power from an engine, one must have a gasoline with adequate flame speed (faster is always better), and adequate octane quality to support the combustion process. Tied in with the optimized air-fuel ratio and the spark timing, we have a winner.

Powershift

I have experienced this with Shell 93 octane V-Tech (with ethanol) and Exxon Extra 93 octane (with ethanol).

However I have recently been using Exxon 91 octane non-ethanol gas mixed with VP 110 octane leaded racing gas. Fuel looks/appears and runs beautiful after 6-9 months sitting in the tank. No hint of degradation.

I know my 1967 car needs more road-time, but not everything goes as planned all the time. However, it still leads a pretty good life.

Larry

LouieM

There is obviously an unknown factor at work here.

Nicola

I have been running regular 87 fuel in my 66 300 hp car for years now.
Flat top Pistons, built to stock specs.
No problem, no pinging more money in my wallet too.

427435

Are you using fuel from the same station?

Are both the regular and premium fuels E10 fuels?

Frankie the Fink

Hence my post #4 test as a sanity check...but the horse has now left the barn on discussing what hi-test is, is not, and, how it burns....

This fella inadvertently fixed some problem with his car coincidental to changing gasoline grades and now has the cause and effect wrong....very simple...

phil2302

I dont see how anyone could disagree with your assessment. Myself included.The odd part however is that despite all the aforementioned fixes, nothing changed for the better till the fuel selection was changed followed by an immediate and dramatic improvement.
Plan is to run it down to 1/8 tank and put some 93 back in it. (for research purposes ☺) Report to follow.

Frankie the Fink

These are old cars with some finicky parts....trash in the carb, a temporarily bad acting float, a sticky distributor weight all can correct themselves at inauspicious times leading you to think the symptoms were related to something else. Several decades ago there was a big issue with older gas stations in ground tanks going bad and water in the gas (for some pumps) was fairly prevalent in the Tidewater area....now that could cause some weird problems that could be attributed to a dozen other things.

Your report should be interesting...

MikeM

None of your symptoms have anything to do with octane.

Yes, I have seen it before on several occasions. Once when I accidentally dumped diesel fuel in my garden tractor and more times than I can remember over the years when I had water in the gas. None lately though.