dumb question of the day...

Leaded

YES

leaded gas

The lead was a lubricant for the valves. If you have modern heads or have replaced the valves/seats with modern parts you are o.k. If you have original valves/seats they will wear out faster. There may still be lead additives for gas but I doubt they are legal in Germany.

No it will not hurt to run Unleaded gas.

This is seemingly a continual myth.

Lead in gas was designed to boost the octane ignition...the lead had a favorable side effect as a lubrication. The engine does benefit from this, however it is not nessasary unless you are running your engine at very very high RPM's for very long periods...ya know Daytona 500 type run.

Google with the angle I gave you and you will see. It is very easy to keep carrying this myth unless you are told otherwise. I learned this from an advanced Engineer in the Engine industry.

lead

Very interesting! I'm all for busting myths. I just did some research and found plenty of info to back up MarksFastBack. Among the many discussions I found this was the best (although I can't vouch for the accuracy of the author):

Ahhhh...........mythology vs reality!


Now the lead thing. (abreviated version, I'm short on time this morning) These myths just don't want to go away, I guess because folklore is so comforting. The ONLY reason tetraethyl lead was introduced into gasoline was that it was the most economical chemical compound that contributed to higher octane ratings of fuel. All the BS about lubrication is just that..........BS. In fact, when all the science guys were searching for the "magic potion" to increase octane rating during the early part of the twentieth century, tetraethyl lead wasn't their first choice. As often happens there was significant difference of opinion in the community. Lead, even then was know to be hazardous (though not hysterically so). And it contributed to significant depositing in the engine and exhaust system. Since it was so inexpensive it won out anyway. The science guys figured out a way to put another additive in the additive to help keep deposits to a minimum. They're called scavengers, because they scavenge the unwanted deposits out of the combustion chamber. The main reason for bringing this up is that this whole fairy tale thing about the magic lubrication qualities of lead is bunk. The formulators of gasoline did as much as they could to get that stuff out of the engine. Since they weren't 100% successful, there were some deposits left behind. Those deposits, consider them contaminants, dirtied the exhaust valve seat and face which kept the two hot surfaces from "welding" together. It's that welding and subsequent tearing that caused exhaust valves and seats to errode. Dirty surfaces don't weld well, that's all lead contributed. I suppose if you're really stubborn you could twist that into a lubrication scenario of you wanted to. Note too that lead oxide(the result of the burned lead compound) doesn't have any contact with a correctly functioning intake valve.

In order to get the lead out two primary chemical compounds were used. Ethylene dibromide or ehtylene dichromide. The kept most of the lead in a gaseous state for a while so that the exhaust flow would carry it away. Of course these halogenated compounds became corrosive in the presence of water...........which the combustion process is loaded with. Wonder why spark plugs and exhaust systems last longer now a days (probably a question more meaningful to geezers). Sure there's an element of better materials (platinum plugs and aluminized or stainless exhaust) but it's also due to less corrosive elements in the combustion/exhaust stream because of the abscense of those lead scavengers.

Excellent! .... good info .... thanks ....

You've both made a good arguement for not using a lead substitute, but my having actually seen heads with non-hardened seats with the valves sunk into the heads from extended running on unleaded gas tells me otherwise. The appearance of induction hardened seats and seat inserts went hand in hand with the disappearance of lead additives in gasoline. Wonder why? The octane boost qualities of tetra-ethyl lead was a favorable by product, not the primary use for it.

hotrodredneck said:

dangit...how can I run unleaded in it?...being in Germany?...anyone know?...will it hurt it to run unleaded?

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Your engine will be fine with unleaded, but you should occasionally add some lead or lead substitute to protect the valves and seats. Extended use of only unleaded fuel will eventually cause the valves to pound themselves into the seats.

D.Hearne said:

You've both made a good arguement for not using a lead substitute, but my having actually seen heads with non-hardened seats with the valves sunk into the heads from extended running on unleaded gas tells me otherwise. The appearance of induction hardened seats and seat inserts went hand in hand with the disappearance of lead additives in gasoline. Wonder why? The octane boost qualities of tetra-ethyl lead was a favorable by product, not the primary use for it.

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I'd also like to attest to this. If lead additives aren't necessary, why in the world have the old cast heads I've seen sunk their exhaust valves in the head without hardened seats?

As was said, you'll be fine. I'd suggest running a leaded race gas in it every so often, replacing the seats with the hardened variety, or putting aftermarket heads on it

Oh and I'm an engineer too.... Sometimes our studies teach us things that aren't 100 percent applicable in the real world. I will research this in my books and get back to you with a more educated answer.

I am very careful here being a very happy new member.

May I suggest a possible answer to the hands on and real observations.

If I may...It is possible that you have witnessed what you have seen because that engine had a problem (what about the mass of others that have not). This going to be hard to describe what I want to get at,

Ok...lets say 1,000,000 engines were made (and they were) out of all the engines out there from the lead gas days how many actually had this problem. It would seem that all engines would be damaged to truly convict unleaded gas.
Can the problem as described be cuased by race fuel,extreme RPM's with a hot plug gap?

I respectfully wish to bring up these posibilities becuase I am a person that recognizes the curses of assumptions.

So how do I ask a question in type and not sound argumentative...because I am not. I truly believe that anything is possible and if a senario needs cause, focus can sometimes meet be misdirected to meet an explaination much like a survey.

What I mean is this, I am not a Master Mechanic...I am , however an extreemly logical thinker and love problem solving.

D.Hearne said:

... but my having actually seen heads with non-hardened seats with the valves sunk into the heads from extended running on unleaded gas tells me otherwise.

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...does this mean that until unleaded gas this had never ever happened to an engine before. I do not know the answer...but I would like to know because it certainly would "be an interesting answer"

I am a very respectful person and wish to know why this may be a myth...

Why do valves sink into heads...I believe in Murphy's Law...if there is more than one way this can happen then we may have to consider and share these causes in the very least.

Sometimes conviction is misplaced...I wish only to make an appeal on the behalf of unleaded gas.

I'm not talkng about race engines or modified ones. I've seen dozens of stock O.E. heads sitting in machine shops with sunken valves. Race engines really wouldn't have this problem as most are not run long enough for it to become a problem. It's not something that's going to happen overnight, hence the reason I suggest that he occasionally run some additive, the problems take quite some time to have an effect. Running unleaded without hardened seats doesn't kill every head or valve/seat, but it DOES damage over time. I've also heard that too much additive causes plug fouling, I ran an additive in my 68 Merc's 390, just as a precaution, but didn't add some with every tank. I can't tell you for certain it helped, I've recently sold the car and had no reason to pull the heads again after a few thousand miles just to check for seat wear. From personal observations and believing in the old saying "better safe than sorry" I'd run at least some additive.

D.Hearne said:

You've both made a good arguement for not using a lead substitute, but my having actually seen heads with non-hardened seats with the valves sunk into the heads from extended running on unleaded gas tells me otherwise. The appearance of induction hardened seats and seat inserts went hand in hand with the disappearance of lead additives in gasoline. Wonder why?

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I have a set of original 289 heads in the garage that came off my old '65 Mustang. Being original, they have plain iron seats and at least two sunken exhaust valves in each head. I agree about hardened seats showing up as leaded gas disappeared. Car manufacturers would save one cent per car if they can, so they certainly wouldn't go to the extra work of putting seats in the heads if they didn't have to.

I agree with Hearne. I have a set of heads on my workbench to prove it. This isn't the first time.

While the damage and wear characteristics may be a bit overhyped. it really happnes, and car manufacturers took expensive steps to correct it. No way they spend the money unless they have to.

So if you have an older engine and it has sunken valves

...it is because of unleaded gas? No other reason?

How about
..hardened seats prevent sunken heads...because the seats are hardened, regardless of gas

How about
...soft seats get sunken valves... because the seats are soft and not because of gas.

I guess I do not go with assumptions.
Perhaps around the time unleaded came out the engines were getting alot of miles on them and that was the reason.

Antique boats do not have the market cornered on the lead gas issue either.
However they do not have the same amount of run time.

Unless I see an actual test from a new soft seat motor and the test shows it had immediate problems leading to sunken valves, then I must contend observations that state examples of sunken heads and point a finger to the gas is presumptuous and hind site with out "actually" knowing.

How about pointing to soft seats and high hard miles? With this scenario it lends a hand towards
"How" the miles were put on, and not
"That" they were put on
...and this seams more logical bases as to why only "Some" engines have this problem.

Because...it would seem logical that if it were the gas "All" would have sunken valves if all were now using the damaging "unleaded" gas.

Ok, how about this: If sunken valves were a problem that was solved by hardened seats and not fuel, why were they never used until unleaded gas appeared?

The 289 heads with sunken valves that I have came off the seemingly good running engine that was in the car. I suspect there are many other low performance engines out there are are running fine while the valves keep sinking. No one can really say how long it takes and I have no idea how long it took my 289. It could have been 10,000 miles or 50,000.