rcread

Not to mention that studies have shown that the additives we now put in gasoline are more dangerous than the lead that used to be in it.

zwede

Cite?

Vette5.5

Recall when car's were switching to unleaded fuel, regular leaded was still around for awhile. Was cheaper and a few point's higher, so many pulled the cat's and punched out the filler neck's to use it. With 93 unleaded common in my area now, really don't give it much thought. Some state's kept leaded regular around for year's. Was on a ski trip in Taos New Mexico in the mid 90's, and they still had it availible. Not sure what for, but maybe farm equipment.

Indiancreek

The lead was removed for emission reasons. Then the valve seat issue was discovered. Seat erosion was the result. Cure was the hardened seats. Small adhesions of the valve seat to the valve face took place and the valve upon lifting pulled the adhesions from the seat. In time the seat material removed will let the exhaust valve lower into the roof of the combustion chamber. I've seen them, under normal driving use, with the entire exhaust valve below the roof of the chamber.
Only takes place , for the most part, with the exhaust valve. Normally more pronounced with the two center exhaust valves do to the heat developed by the exhaust being next to each other.

forvicjr

my 76 ray

My memory may not be correct, but, I think I remember unleaded becoming popular in '75 because it was necessary for the catalytic converter. Prior to that the only unleaded I remember was Amoco Hi- Test. I can't imagine all the manufacturers putting in hardened seats in '71 because of one grade of one company's gasoline. Although, I do remember reading somewhere that Amoco unleaded users may have needed more valve jobs.

mrvette

Even though they did advertise No or Lo lead, they did have lead in their gas, but yes Amoco was first to make a big deal over this, almost 40 years ago....

25% more crude consumed for 40 years, that's a decades worth of totally un necessary crude consumed, then we wonder why prices went up.....

thanks green weenies, bunch of idiots....spring off from Ralph Nader....

zwede

Please explain. TEL was an additive. Now we have better additives that don't cause brain damage like TEL did. Why would adding additive B instead of additive A use 25% more crude?

Mike Ward

You're forgetting (or didn't know) that the rating system for gasoline also changed about the same time as the introduction of unleaded. Today's 93 is the same as 98 or 99 in the 'old days'. Europe still uses the old system which makes many believe that they have higher octane gas than us.

And once again, I'll ask for proof of any Corvette heads that have suffered valve recession due to lack of lead. The claim that 'they've all been modified' is false.

mrvette

Like posted above, the articles in the Wash Post paper around '73 or so, and them clearly saying it took 10% more crude/gallon of gas to make unleaded than leaded....their article, I would assume source was some oil company maybe the industry...at any rate that hot button will not be touched today....except by ME....

then me noting a solid 15% reduction in fuel economy.....I used to drive 20 miles one way to work, that reduction HURT, especially with all the price increases....cut into date money...

and it was not JUST ME that noted a similar reduction in economy, friends and even my father noted the same thing.....

so do the math....25% more crude consumed/mile traveled/gallon used.....

lovely thought, eh??

eff the weenies forever,

and what's all this ill health supposedly brought on my leaded gas..?? see pilots and old gas station mechanics falling over right and left ?? seen it back then?? or something fed a lab rat to abject overdose the the rat finally dies, so they claim it's harmful???

Mike Ward

Well, no post on the CF would be complete without a good conspiracy theory.

Indiancreek

I probably still have sbc heads from the early 70s era laying around the shop someplace that have eroded exhaust seats. Whether they were from an Impala or a Corvette is inconsequential. A casting number is a casting number. Valve sizes were different among the same cast number, but the heads themselves were the same. I've taken 461s and 461x's out of grocery getters in those days. Back then it wasn't uncommon to find a four bolt 300 hp sbc in a station wagon.
When you could order your car the way YOU wanted it then there were all kinds of possible combinations.
The last set of 461s I put seats in were so eroded that I was reluctant to cut it for inserts. Without sonic test results I would have probably passed on the job.
I have a publication from an engine builder organization I belong to that addressed this very issue. If I can find it I'll get some of the information from the article.

markids77

There's a reason they changed the size of the filler hole when catalytic convertors were introduced...a simple deterrent to leaded fuel usage. The lead coats the matrix in the convertor, keeping the catalyst from contact with the exhaust stream rendering it ineffective. If you run a convertor equipped car on leaded fuel for long enough, the matrix may plug solid and cause extreme back pressure, with predictable deleterious effect on your car's performance. Is no one else here aged enough to remember this transition?

Mike Ward

Uhh, ya it is and makes all the difference in the world. The ONLY SBC or BBC heads that were damaged came from heavily loaded applications running for long periods of time, like grannie's station wagon pulling a house trailer up the side of mountain. Or a dump truck, motor home, boat etc etc.

Corvette engines never ran hard enough for long enough to do such damage. But the myth lives on...........

zwede

Maybe that was true in 1973 when the refineries were still adapting to unleaded. Hardly true today after 40 years of improvements.

69 Chevy

There were 2 pumps in front of my local general store in the 50's and 60's...Flying A brand. One pump was labeled Ethyl...that was low octane but there was no sticker saying what number or how it was determined.

The other pump was labeled Hi-test. All the hot-rodders that didn't want (or need) to travel to the far off Sunoco station for 260 said, "Fill 'er up with Hi-test." I don't know how much octane that was either. But I can remember the last price before they tore them and the steel underground tanks out...32.9 cents!

Which makes me wonder why no other retail commodity is priced in tenths of a cent??

mrvette

I knew you were going to go there, so why I ask does AVIATION gas still have lead in it....or up to very recently, if not now exactly.....

81pilot

zwede

Dunno, never played around with planes. I guess it is a case of government bureaucracy. TEL is the only approved additive for octane in aviation fuel and it takes forever to get an alternative approved?

Maybe since the exhaust is up int the air (so to speak) it will have a greater chance of dispersing before people come in contact with it.

BTW, I did find info on that NASCAR banned leaded fuel in '08 after crew members tested positive for elevated levels of lead in their blood.

Mike Ward

Nothing to do with government bureaucracy. Most aircraft engines that require high octane leaded fuel were designed, certified and manufactured back in the 50s, 60s and 70s. The cost of redesigning and certifying affordable (key word affordable) engines that would run with the same power output on lower octane gas without damage is something no manufacturer wants to undertake.

The cost of modifying existing engines to run on low octane gas is horrendous, frequently exceeding the value of the aircraft itself never mind having to accept greatly reduced power output.

Since the market share of avgas is tiny (0.5%) as compared to cars, there's not much to be gained by forcing it out of production.