The Stovebolt Site Forums The Shop Area Engine Shop Premium gas in the Blue Funk

The Blue Funk (see my signature) had been a little difficult to start now and again since it's been back on the road last May.

There was nothing was really consistent (that I could tell) about the trouble starting, whether cold or warmed-up. The engine always started- it was just a combination of choking, pumping the pedal, pedal to the floor, encouragement, pleading, whatever. Once it started, the engine ran fine.

I stopped by the Gas station, and due to repairs (I guess) premium was the only gas available. I thought, what the heck? a few gallons won't hurt it.

What a change! The engine fires up first time, every time and runs like a champ!

Tell me what you think.

Thanks!

High octane gas shouldn't be necessary with the compression ratio your engine has. It might be coincidence, but if it helps, the only downside to running high test gas occasionally will be a few more bucks out of pocket when you gas up.
Jerry

Thanks, Jerry!


Are there any other downsides to regularly running high octane gas than the money?

I found running a better grade of gas gave me a slight boost in fuel mileage. Maybe not enough to justify the cost difference, but it did run a bit better. Don't know of any downside.

There might be a slight increase in exhaust manifold temperature, as premium gas burns slower than regular and some of it might still be burning as it leaves the cylinder. You can advance the timing a few degrees if you run premium all the time and get the burning process started a little sooner. Just be careful not to advance it so far that the engine pings when running regular gas.
Jerry

I have always run regular gas (87/89) octane but.....one day I was at friends and did a quick carb adjustment on his car and he threw a bit of aviation gas in my truck ..54 with a 235. Now that woke it up.at that time it was runnig oem points and condenser it started quick and pulled nice.ran the av gas that one time only. The only time since that my truck started that nice was when I put a hei dist.in....edit...av gas was mixed in with a half tank of reg gas not straight av gas.that would not be good

Thanks, Guys!

Before ethanol:

A gallon of 87 octane regular contained 117,600 Btu/gallon
A gallon of 89 octane contained 117,600 Btu/gallon
A gallon of 91 octane contained 117,600 Btu/gallon
A gallon of 93 octane contained 117,600 Btu/gallon
A gallon of 100 octane avgas contained 117,600 Btu/gallon

Ethanol (according to the scientists, not the government) contains 67,000 Btu/gallon.

Ethanol is often used as an octane booster as the AKI octane of ethanol is 116.5.

Mixing gasoline and ethanol will ALWAYS result in less Btu/gallon than any grade of unadulterated gasoline.

As Jerry mentioned, the higher the octane, the SLOWER the fuel burns. Often, higher octane fuels will NOT completely burn in a low-compression engine, resulting in both a loss of power and fuel economy. This is certainly true of avgas.

If one does find the higher octane fuel (or avgas) is working better than one's current fuel in these lower compression engines, then one should try the same octane fuel as before FROM A DIFFERENT STATION! Possibly the current station's tank has some contaminents or???

Now if one has a 13.5~15:1 compression race engine, then the avgas should work well.

My shop truck (not a stovebolt) runs 10.28:1 (measured when we built the engine, NOT advertised) compression. Under normal conditions, I run 87 octane fuel with NO issues. When I pull the 16 foot trailer, I put 89 octane fuel in the tank.

Seriously guys (and gals), the lower compression engines should run WORSE on the higher octane fuel PLUS it is more costly.

Jon.

Practical experience leads me to say other wise. The old 261 would run a bit smoother and do a little better on fuel mileage using the higher grade fuel.

I'm not a scientist so can't explain the why, and perhaps my results aren't typical.

But I also know the old engine would run better on gasoline before the ethanol was added.

Huh! Go figure!

Thanks for the info, Jon.

Could it be, that since the Blue Funk ran well on regular fuel and the difficulty starting was the only issue, the higher octane fuel is merely a shot in the arm; a kind of boost, to get it going?

Okay- What IF the timing had already been too far advanced- would THAT have caused the difficulty starting and the subsequent easy starting on Premium gasoline?

The difference is just phenomenal! I mean, the Blue Funk starts first time every time!

How old was the fuel with which you were having difficulty starting?

Modern fuel goes bad within 3~6 weeks. Hard starting and sluggish until engine is hot, and then will run OK.

Perhaps your issue was simply old fuel.

With my collector vehicles that are started infrequently, I don't even attempt to start on the fuel in the tank. Start with starting fluid and save the battery and starter.

Jon.

I also use starting fluid if the vehicle has sat longer than 2 weeks, works great.

After my '50 has sat for some time, a month or even over the
winter, I just pull the choke out, pump the peddle a couple
of times, when I get fuel up to the carb and it starts right
up. In the 10 years that I've had her I've never had a problem
with it starting, even after setting for a long spell. You
guys must be getting some real bum petrol where you're from.
Haven't had trouble with the generators, blowers, chainsaws,
mowers or any of the motors that have sat with fuel in them
over the winter or even in some cases for years.
Denny Graham
Sandwich, IL

Like they say everyone has an opinion, like ahh, well you know what I mean
I avoid starting fluid (ether) like the plague. It's always the last choice I have when all else fails.

I know it's an old mechanics tale that engines get addicted to that stuff but I've seen diesels that wouldn't start without it once it was used regularly on them. Even in 90 degree weather.

I'm sure the fuel was fresh: I ran out of gas not too long back and a Good Samaritan got me home. I put a few gallons of gas (also fresh)I keep for my lawn mowers in the Blue Funk and drove it into Town for more gas. It wasn't long after that the Premium gas was added.

As I said, the change has been phenomenal: starts easily and runs great!

I've heard that if starting fluid is needed, regularly, the engine is in need of other things, like a Tune Up. Initially, last Spring, when I was atempting to get the engine going after sitting for nearly three years, I did a couple of squirts of starting fluid, but no more.

Anyway, thanks for the discussion, Guys!