The Stovebolt Site Forums The Shop Area Engine Shop 100LL Fuel

Can I run 100LL Aviation fuel in my 216 without any problems?

Is the engine stock? Are you wanting the leaded gas for the valve seats? The only place I could get 100LL is at the local airport and it's a little pricey.

Your engine is designed to run properly on regular 87 octane. If it doesn't, your engine or ignition system needs attention. No need to spend $6.50 to $8.00 per gallon when $2.69 regular gas will work just fine.

Get ready to burn out exhaust valves and have a red hot exhaust manifold on a regular basis. That stuff burns so slow most of it will still be burning as it goes into the manifold.
Jerry

I get the gas for free. I have 500 Gallons of it every 6 months. I sell it to Boat racers and the military vehicle clubs. My WWII jeep loves it. It makes it run cooler. The gas never really goes bad. I mean it can sit in my tank for 7 to 8 months and still is good. It is pure gasoline no additives but lead. My Harley's love it as long as it goes into a carbureted engine that is.No computer engines. It will make the O2 sensors go bad. So no to the 216 ????

Wow, I didn't know it was still possible to buy gasoline with TEL in it at all! Although it seems that a lot of old engines with low compression ratio were designed to run on corn squeezin's if need be, so it seems like that extra octane would be a waste. But hey, if it's free.. :-)

Tronman, 100LL is aviation fuel. It's not legal for street use. It has lower volatility and may result in hard starting in a car. It's designed for engines operating at high altitude, i.e. piston engine airplanes.

The octane rating for Avgas is derived using a different formula than automobile gasoline.

The 100 rating is based on the Motors Octane Number (MON), whereas automobile gasoline uses the AKI rating, which is an average of MON + RON (Research Octane NUMBER).

That works out to an AKI octane rating for 100LL of about 108.

100LL is also known as 100/130 octane. The 100 is the octane rating based on lean mixture conditions for cruising and 130 octane at rich mixture conditions at full power.

I spent years driving a tanker and delivering av gas to assorted general aviation airports (FBOs) in the PNW. It's blue; it's clean and the consignee will have done a white-bucket test and a gravity test on it. After every load British Petroleum, whom we hauled for, required that every compartment be bucket-drained and tested for water before the next load. I kept a 5-gallon can in my trunk and netted that much every day that I hauled av gas. I had a BMW 78 320i and a Norton Commando motorcycle at the time and both were very happy when I came home with a can of av gas. I also ran it in my 51 Chev pickup with a 235 and 8:1 compression. Never a problem. During one fire season I had a daily run from Seattle to Redmond OR to fuel a 4-engine DC6 outfitted as an air tanker that used about 10,000 gallons a day. This went on for over a month. Log books were exempted by the state on orders from the Governor. We ran as many hours as we could stay awake. The Norton and Beemer were happy.

I also hauled jet-A for B-P to all sorts of locations, mostly helicopter applications: logging shows, fire fighting and some FBOs. Same story as av gas on quality; same bucket-drain requirement after every load. The difference was that the drained jet fuel ended up in my old Mercedes diesel car. It was quite happy and I would lube the injection pump with a qt. of ATF that I got the same way as jet fuel; that is until I realized that the state fuel-tax authority could sample diesel in cars and trucks, checking for un-taxed, red-dyed diesel. By that time we were hauling bio-diesel and I used that as a pump lube.

I'd suggest adding a pretty good quantity of non-alcohol 87 octane regular gas to increase the burn speed a little to avoid overheating the exhaust. When I was running an autocross course with a Sunbeam Tiger as a member of the Okinawa Sports Car Club back in the early 1970s, a friend on the flight line at Kadena AFB kept us supplied with 115/145 avgas for that car. We mixed it 50/50 with 87 octane regular and had very good performance.
Jerry

Would changing the timing via the octane selector on the distributor aid in dialing in how the engine runs with that high octane fuel?
That is specifically what the octane selector was designed for. Back when these engines were new, the consistency of the octane which you filled up with varied widely. The octane selector was there to make a simple timing change with nothing but a half inch wrench, and you could simply dial right make to the zero mark without a timing light.

Not going to argue about using the avgas in your engine, rather just stating a fact:

Use of the "octane selector" has already been mentioned.

Stromberg (one of the better carburetor manufacturers) stated that when using street premium fuel in low compression engines, the carburetor needed recalibration. Street premium is nowhere close to avgas in octane.

With 60 plus years experience of working on carburetors, I have found listening to the engineers often solves issues.

The only engines I have found where really high octane fuel works close to as well as the correct fuel are engines that have been HIGHLY MODIFIED. (Race gas works very well in my 350 / 450 with 10.38:1 compression, and 20 degrees BTDC timing.

EDIT: In the "for what its worth" category:

In 1950 "regular" gas would have been an octane of about 80 (RON) which is roughly equivilent to 77 (AKI); premium was approximately 85 (RON) which is about 82 (AKI). Stromberg stated the carburetor needed recalibration for premium (then AKI of 82). Avgas has an average AKI of 108.

Jon.

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