Vettegeezer

So, this got me into thinking: what is so special about aircraft gasoline engines that they require 100LL (low lead), fuel? Constant high load similar to a race car engine or towing? Are newer aircraft engines still built to require LL, or do they have the capability of running no-lead fuel? Just curious.
Phil

Frankie the Fink

I just don't know why you wouldn't buy commonly available oil with sufficient ZDDP levels already in it ?

And, I didn't even look at the "cases" where lack of lead caused problems... I know dozens and dozens of classic car owners and none of them run lead additive and have used their cars regularly for decades with no issues... I'll take first-hand info over internet stories every time....

Seriously, run with it if you think its helping.....your money, your car....

SWCDuke

There used to be four grades of avgas, but as demand dropped, all were consolidated to 100LL. Some smaller engines don't need that much octane, and I believe the FAA allows the use of 87 PON mogas in some small engines. Getting type approval for changes to these engines is a long and costly process, and most general aviation aircraft engines were designed in the forties.

100 percent power is required for takeoff and cruise is usually 65-75 percent, so aircraft engines operate at much higher average load than a typical automobile engine. That's why the aviation octane rating method yields numbers very close to the MON method, which is a more severe test than the RON method.

Duke

dplotkin

I'm sorry for last evenings wise guy response. The problem with additives is the voluminous opinions as to their efficacy. Some say the danger of valve seat recession lurks in the shadows, others say only if you are towing a loaded Airstream up steep grades weekly. Some say use ZDDP or your cam lobes will resemble old fashioned roller skate wheels by evening, and others say that is true only when using steep ramped cams or high pressure springs. We have folks here who swear they have encountered no difficulty with today's alcohol infused gasoline and there are others who insist the stuff is poison to all manner of fuel system rubber parts. Guys here say 134A won't cool as well as R12 and I have both and either one cools to 38 degrees. So the problem is too much information. Opinions are not unlike the posterior vent on the humanoid. They are everywhere and on average they don't smell very good.

So I read a lot, mostly shop manuals and engineering journals, and I synthesize what I learn into my automotive way of life. The condensed version is this; I use a zinc fortified oil (Brad Penn) 10W40, and I change it when it begins to darken on the stick, usually once a year, sometimes once every two. I never start a car unless driving it to operating temperature. I never put them away dirty, never. I burn high octane pump gas and the one year I skipped using Stable in the fall I had carb issues on 3 of my 8 cars. I don't use other additives except for one time I put Barrs Stop Leak in my 63 Impala for a weeping freeze plug. Fixed that in a Jiffy.

I take a hand full of vitamins along with my Lipitor & Flowmax (not the muffler) every morning and I feel pretty good and the cars run well, so I keep on keeping on.

Happy 4th!

Dan

SDVette

Well, the forum would be boring if we all had the same opinions... I appreciate the more thoughtful reply!
Frankie -- love you.. but if you won't even look at the evidence I post, I guess we just have to agree to disagree.

Duke is right about light aircraft engines and leaded fuel. That industry has been declining for decades.. and it's highly regulated for safety. None of the remaining few manufacturers have a business case to go through a complete certification to get an engine approved for unleaded gas.

One interesting tid-bit I'll mention (from one of the cases I posted) is this: IF the seats are receding, a tell-tale sign is that valve lash on the exhaust side requires constant "loosening". As the seat deteriorates, the valve moves lower in the head. So keep your eyes out for that!

Happy and safe 4th to everyone!

boxster99t

Perhaps I missed it in all of this thread, and if so, I apologize. When the engine was brand new or rebuilt, yes the valve seats benefited from the lead in the gas for lubrication. After some miles, all the lead that ever needed to deposit itself on the valves is there, and you no longer need the lead even if your engine has not had hardened valve seats installed.

Unleaded pump gas works just fine in my 327/300 HP--I run 93 octane. Unleaded gas is the best thing that happened to engines--don't know about you, but I like not having to change spark plugs frequently. Back in leaded gas days, we had some cars that you either had to replace or remove and clean spark plugs every 8,000 miles or so. Don't miss that at all. Probably why Champion which was a big company headquartered in Toledo Ohio (I'm originally from there) is a shell of its former self and was bought out--replacement spark plugs are not the big business it once was, now that there's no lead in gas to prematurely foul up spark plugs.

Tonio

Exactly! I've opened up my engines and I see there is no damage. First hand indeed. I'll trust my own eyes before I trust internet stories about classic car owners. ;-)

domenic tallarita

I agree with what you said about the lead. I am friends with the local engine shop owner and he was at a seminar that said the use of lead for a few hundred miles will impregnate what is needed, after that it doesn't matter. I am about the only one that needs 100LL mixed with my high compression engines tuned to factory spech. If I don't they ping!

Dom

MikeM

Your potential valve seat recession is but a tiny part of a much bigger world. A few excerpts taken from here:

http://www.meca.org/galleries/files/111698_lead.pdf

Leaded gasoline presents a serious inherited public health problem thrust upon the leaders of this generation. This paper makes the health, technical, economical, and moral case for those leaders to act to ban leaded gasoline. The paper focuses on the following points: ß Airborne lead is a cumulative neurotoxin ingested by humans, adversely affecting the mental and physical health of children, and causing elevated blood pressure, hypertension, and other cardiovascular conditions in adults. ß Unleaded gasoline, known as a clean fuel, makes economic sense as it improves engine and component durability alike and reduces maintenance costs. ß Those supplying lead for gasoline argue that unleaded gasoline contributes to valve wear and higher benzene emissions and, therefore, justifies the continued use of leaded gasoline. Countries that have eliminated lead in gasoline have considered and rejected these arguments. ß There is economic justification to switching immediately to 100% unleaded gasoline. China and India are doing this now

Subsequently, in the early 1970s, engines were redesigned again for unleaded gasoline. Hardened valve seat inserts were introduced. Older engines were thought to be susceptible to valve seat wear if operated on unleaded gasoline. Actually, valve wear has been found in several studies of older engines but only at high engine speeds and loads in engine dynamometer studies. However, in actual use, older vehicles in the United States valve wear did not turn out to be a problem in this respect. Many older vehicles used the clean burning unleaded gasoline (a brand of AMOCO premium unleaded gasoline had been on the market since the 1940s). Also, many vehicles were converted successfully to LPG fuel (an unleaded fuel).
2.4 The Benefits of Unleaded Gasoline to Vehicle Maintenance Unleaded gasoline considerably reduces the vehicle maintenance costs incurred with leaded fuel use. Unleaded gasoline is a clean fuel with less corrosive products of combustion than leaded gasoline. Consumers benefit from maintenance savings and fewer engine and exhaust system repairs due to corrosion. The additives EDC and EDB, needed in leaded gasoline, form corrosive acids upon combustion. They cause corrosion to engine parts, more frequent oil changes, and the replacement of spark plugs, mufflers and exhaust pipes. As a result of switching to unleaded fuel, several nations, including Australia, Canada, and the U.S., have reported maintenance savings in the range of US $0.189 per gallon (US $0.05 per liter) of gasoline [23]. The economic benefit in terms of savings in vehicle maintenance costs alone justifies the removal of lead from gasoline [18]; along with health benefits, the arguments become even more compelling

domenic tallarita

Duke,
Yes, your right, the smaller engines that can't reach higher altitudes can use auto fuel. The requirement was premium and no ethanol. Not to many around here got the approval and buy what ever they can at the pump and pour it in. One problem I saw was high EGT (exhaust gas temp) on one. You can always lean the mixture in flight, but can never make it richer than the main jet. I know you are familiar with all that, but for some history benefit for the other readers was that the 4 blends of av-gas used a 3 letter code for the lowest and increased the letters as the octane got higher. RED-- blue-- green--purple. That was the color of the fuel so you could tell what you had in your tank. Mix any 2 together and the fuel lost all color. A valve angle change from 30 to 45 degrees was require to use 100LL when the red 80/87 red was discontinued.
Not sure those rules are being followed.
The beauty is that av-gas doesn't turn to varnish. It was posted here to have a shelf life of 1 year, but I have some vintage motorcycles that are rode every few years and av-gas in them over 10 years old and have no problems.

Dom

SDVette

I have heard the "lead seasons the valve seat" theory.. I don't dismiss it. Maybe it explains why there aren't more problems..? Especially in classic cars that would be less likely to 'scrub' the TEL since they typically don't rev high, under load, for long periods...

However, that theory has also been applied to the ZDDP/flat tappet problem.. The theory is that once the cam/lifter surfaces have been hardened, you don't need the zinc/ZDDP any longer????
We will probably never know with 100% certainty.

Also, just want to be clear that I agree with EVERYTHING MikeM said about lead.. It's nasty.. It was a costly decision to introduce it into motor fuel in the first place. I only run a few ounces with a full tank; a bottle usually lasts me 6 months. I watch the plugs carefully and see no fouling.

Frankie the Fink

I'm '67 and in damn good health generally....my Dad and I used regular leaded gas to wash the grime off our hands almost daily when working at his used car lot in the 60s....

I know its dangerous stuff but as with most of these things its prob hyped....
I just looked in the mirror and I haven't grown a second head yet....

SDVette

My dad and I used regular leaded for everything too.. from cleaning oil stains, motorcycle chains, killing ants... you name it!
I recall seeing my father cleaning parts in a tray of gasoline... lit cigarette hanging from his lips!

Ah, the good 'ol days!

BTW: There is a blood test to check for hydrocarbons in your system. I heard Edd China (from Wheeler Dealers) tell the story that he got a positive result on that test a few years ago, and that's why he always wears the orange gloves.

MikeM

My link didn't address absorbing lead through the skin, it talked abour BRAIN damage from breathing the lead, Check for symptoms other than what you see in the mirror. .

domenic tallarita

Mike,
Enjoyed your research, unfortunally it was 65 years late for me. I had my arms in gas up to the elbows cleaning parts. Did it effect me? I would have to say yes! My body has absorbed so much crap that I get a nasty taste in my mouth when I touch gas (pump) or jet fuel! But personally I like the taste of leaded fuel over unleaded!

Dom

Vettrocious

Here's the deal: every fill up, don't put in the additive. Send me a check for two thirds the cost of the additive. When you've put 100,000 miles on the engine, tear it down and take pics of the valve seats. Send them to me also. If they are receded, I'll send you new heads. You'll never have to worry about additive again. Any questions?

cv67

most these cars never see anymiles, the topic is almost irrelevant.

phil2302

Of course! And yet this same topic will be back again in 3-4 months.
Happy 4th!
I am going to take my 66 out this morning and continue the 32 year process of ruining my cylinder heads.

juanvaldez

Aircraft engines are air cooled, low compression and slow turning. The compression on my Lycoming 0-320 is 7:1. It was designed to run on 80/87. I can burn Mogas by just adding a placard. Aircraft engine operate at a much higher percentage of power, 100% to climb and 75% to cruise. Imagine running the 1/4 a few times a day and then cruising at around 130. Also, since aircraft operate at lower atmospheric pressure at higher altitude, volatility comes into play. Aircraft fuel was also color coded by octane, 80/87 (red), 90/97 (blue Blue Goose), 100/107 and the newer 100 LL (green). Mix 'em and they go clear.

Vettegeezer

Haven't seen anyone mention it, but the raw, unburned leaded gas also smelled better than the newer stuff!