100LL vs ??no lead

N

nvracer

New member
I have a 14-13-2 with a 150 Franklin. I use 100 octane low lead fuel. Lead & carbon seems to build up quickly on the plugs & valves. I know that the Franklin calls for 80 octane unleaded fuel, but it seems very hard to find. Do any of you have similar problems? How about solutions?

Thanks,

Ray 33GM
 
hey ray!
i operated a 165 franklin in my 108-3 stinson for over 12 years. although we can still get 80oct here in california, i chose to use mogas for most of that time. i had virtually no plug fouling or valve sticking problems in all that time and the engine seemed to run a good deal smoother on the car gas. plus the $.50 to $1.00/gal savings was nice.
the caveats here are 1) you are now your own quality control inspector (check thoroughly for water, dirt, etc.) and 2) most of the STC's require NO ALCOHOL. this may become increasingly difficult to find as time goes on as most of the refiners have found ethanol/methanol to be the most expiditious oxigenate to use since MTBE has been found to be so problematic.
so, if you can find mogas without the alcohol, i say USE IT! otherwise, see if you can find a supply of TCP and use it regularly although i understand even this has become hard to find lately.
eventually i think the lead will be removed from all motor fuels, but this may take another 5 to 10 years. then the question is: will you be able to operate a franklin at all given the lack of parts and support?
just my $.02 worth.
blue skies,
vic steelhammer & N522A
 
I worked in an overhaul facility for 2 1/2 years as a tech rep and field service tech...... I also filled in wherever I was needed in the shop when I wasn't on the road.
I don't want to go into the big "mogas debate", but I can tell you this...... regardless of what people say, I saw alot of engines that came in from running on car gas, and they had a much higher rate of rejected parts than the engines that were running av-gas. Lead fouling and buildup, while not very convienient is still better in my eyes than no lead for lubrication in an engine that was designed with that lead lubrication in mind.
It's your call..... and I've heard all the answers from all the owners, but I'm just telling you what I saw...... I saw more overhauls in a week than these owners see in a lifetime, but if you want to use the car gas, by all means, go for it.
Just my opinion.......
John H.
 
I found a great article on the use of Marvel Mystery Oil in the military. I know it isn't legal for use in aircraft, but it makes for fascinating reading!
E-mail me if you'd like to read it for yourself.

Dangerous Dave
 
hi john!
i certainly cannot dispute your experience in the engine overhaul business. but one thing to keep in mind is that the franklin 150/165 were originally certified for "...80/87 octane unleaded aviation fuel". that's a direct quote from the original TCDS.
i'm not sure i agree that the franklin requires lead for "lubrication" of the valve stems. tetraethyl lead is an additive used to delay the onset of detonation. that is what "octane" is actually a measure of in motor fuels. i have not found any technical literature which explains the lubrication properties of TEL. can anyone fill me in?
blue skies,
vic steelhammer & N522A
 
Thanks for the input Guys,

The Franklin calls for 80 octane unleaded. I have not tried auto gas yet. I would like to try the Mystery oil as an additive so Dangerous Dave, I would like to see the article on that subject. You can email me at classichunters@charter.net

Thanks,

Ray N33GM
 
Hi guys,
Sorry it's taken me so long to respond to this, but summer is a terrible busy time here, with hay to put up and everybody wanting to fly at once as well.
First of all..... 80-87 was not unleaded fuel until the mid 1990's. There was 1/3 (approximately) of the lead that is found in 100LL, but it still DEFINATELY DID contain lead!! That is something very important to consider here. I just looked at the Type Certificate and it does not say "unleaded" ANYWHERE on it!
The lead wasn't primarily used for a lubrication as you would normally consider it. It was more for the lubrication and cushion, if you will of the valve seats than it was for the lube of the valve stems. This is why you need to have the seats changed and quite often the valves changed in an engine that was originally designed to burn a leaded fuel, when you start to burn unleaded.
We had a brand new R-985 on one of our Ag-Cats in the mid 90's and had always run them on 80-87 fuel, but unkown to me, they had removed the lead from 80-87 since we had run any brand new engines. The engine lasted about 125 hours before it smashed out the valve seats on 5 of the 9 cylinders. When I started trying to figure out what had happened, I ran into Gordy, from Kenmore Air Harbor (they run a whole slug of Beavers and other float planes) and he told me they had the same thing happening. He finally switched to 100LL for at least the first 300 hours from an overhaul and then things seemed to be fine. We just decided that cleaning plugs was a small price to pay for reliability....
But that's just what I've found.. I've had alot of people argue with me, and they're welcome to their opinions, but I've been on the working end of this problem and have seen the results, and know what I do to make ME feel better.
John
 
hi john!
my reference to 80/87 unleaded aviation fuel comes from the original franklin and stinson operations/overhaul manuals. the current TCDS are being "revised" to delete any references to 80/87 oct fuel. i know this from looking at the lycoming O-540 TCDS. it used to say 80/87 but now says 100LL.
i cannot dispute your experience with the leaded fuels in radial engines. but i ran my 165 franklin for over 12 years on primarily autogas (no alchohol and before MTBE) and never had any problems. no lead fouling, no cylinder or valve distress, and much smoother operations. of course it would get an occasional taste of 100LL when we were out on "the road" but mostly it was unleaded mogas. of course now it's mostly a moot point as the alchohol is almost impossible to avoid and so we're back to the 100LL. sure wish the feds would approve the 91/96 unleaded stuff like they use in sweden. would solve alot of problems.
can't say why i had such good experiences, but that's my story...and i'm stickin' to it :lol: !
blue skies!
vic steelhammer & N522A
 
While working as an apprentice A&P, the AI told me that leaning the mixture right after takeoff (when using 100LL) helped keep the plugs clean.
A Cessna Ag Truck (forget which engine) who had the chunky black stuff between the spark plug electrodes tried this leaning technique. He had noticeably less fouling.
I guess the thing to remember is to be careful leaning at low altitude so you don't end up in a bean field somewhere with fuel starvation.
I won't mention names, but the AI was a great advocate of MMO.

DD
 
Hi Vic,
Well, it seems to me that you missed the point of my letter. The manuals, and type certificate data sheets all mention 80-87 octane fuel..... but I can't find the word "UNLEADED" anywhere in any of them. Also, we used to use "LEADED" regular car-gas as well with great success in lots of different airplane engines. But, you said it yourself.... "before alcohol and MTBE".... the fuels that we get today have very very little in common with the fuels that we got even 10 years ago! I'm not going to argue that lots of people have gotten years out of an engine while burning car gas in them... I've heard lots and lots of people's stories... but when you really dig into them, usually it's with the older fuels, and man, do I ever wish they'd come back again!! I'd love to have REAL 80-87 (or even REAL "regular" car gas!) to run in my Franklin, Pratts, and Wrights..... but that's not going to happen.. so in the meantime, with the experiences that I've personally had, I'm headed to the 100LL pump.. I agree with you totally about the 91-96 fuel....that would help all of us that are trying to keep these old engines running! Oh well... I guess we can just wish and wait.....
John H.
 
hey john!
i don't mean to sound argumentative but actually, i did not miss what you had said. the ORIGINAL stinson/franklin documentation says "...80/87 Octane Unleaded Aviation fuel." (i'm holding it in my hands as we speak). what has happened over the years since 1946 is that the FAA has "revised" the TCDS to have the fuel requirements reflect the fuels that are currently available, not neccessarily what was certified. for example, the franklin 150/165 was NEVER certified to run on 100LL! we may run it in our franklins only because of the "...next higher octane available..." clause contained in the FARs.
your observations about valve seat distress are interesting and worth noting. but based on my experience i still think that the franklin (and most low compression aircraft engines) would be better off running on unleaded mogas (alchohol FREE) than on the relatively high lead content of 100LL.
please know that i value all the discussion presented here and feel that everyone's experience is worth considering and taking note of.
blue skies,
vic & N522A
 
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