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Old 03-31-2007, 03:57 PM
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Why Lead?

I have heard so many things on why lead was used in engines. Sounds like it was just because the valve seats in early engines were soft. I understand that the valve seats would recede from errosion with non lead gasoline.

I have an old flathead 6 from the stoneage that I am building and I'm replacing the valve seats. Do all I need to do to avoid this leaded mess is just get harder materials valve seats?

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Old 03-31-2007, 04:18 PM
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You are right with keeping the valve seats hardened. That was one of the two reasons for ethyl-gas. The second on is that the tetra-ethyl lead is a excellent octane booster.

I cant tell you if the valve seats are soft on your flattie, but the leaded gas will be good for it!

Some race gas and Av (Aviation) fuel still has lead in it.

You can use still use it on any carvureted vehicle, as long as it does not have a catalytic converter. It will clog up the cat in short order!! Your will also have to clean the plugs every once in a while, but other than that, it should be problem-free.
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Old 03-31-2007, 05:33 PM
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So you think in the long run I would be better using the existing seats or just swaping them out for hardened?
If I cant find hardened I'll run lead, i have before on my 53 buick just this is my first total engine flathead tear down.
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Old 03-31-2007, 07:13 PM
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You do not have to buy pre-added ethyl gas. You can buy a can of lead substitute to throw in your regular "white" (unleaded) pump gas. I dont know is it really does anything to your octane rating, but it will save your seats!
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Old 03-31-2007, 07:59 PM
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Yeah I know , i used the additive in my old buick cuse it original 322 nailhead and i was under the impression it have soft seats.
I think with the flathead I will just change out the seats, was just wondering if the seats were the only reason for leaded gas other than antiknock
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Old 03-31-2007, 08:00 PM
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People, The lead in the gasoline served two functions. First and for most it slows the burning rate of the gasoline. So Octane ratings were higher but very poor gasoline could be made "better" by adding more lead. The second is the cushining effect of the lead between the valve face and the valve seat. So as the valve closed it would trap a very small amount of fuel in the mating surfaces. The valve would keep closing but the lead would get squeezed which would slow the valve down. When the lead was no longer added to the gasoline the valves would HIT the seat very fast and hard. This resulted in the valve spring pulling the valve into the seat over a period of time.

Scholman
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Old 03-31-2007, 08:03 PM
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Thanks for explaning what EXACTLY happend. Now I now. I knew what could happen, just didn't know the technical aspect.
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Old 04-01-2007, 01:29 AM
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Lead is an excellent high temperature lubricant.
Without unhardened exaust valveseats and running unleaded gas will cause teh valve seat to erode.

peace
Hog
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Old 04-01-2007, 06:27 AM
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leaded gas revisited

Leaded gas didn't exisit before WWII. Everyone ran unleaded. Even into the mid 50s unleaded was common. Unless you are flogging it leaded gas is not necessary in even a 10.5 comp engine. Note that I did not say that you are going to get by with 87 octane unleaded although under easy driving conditions you could. There are many preunleaded cars driving around today on unleaded. I have a couple myself. While I do use an octane booster, I don't use lead replacers. The only thing I can see they do is foul plugs quicker. The "fact" that lead cushions the valves is a bunch of bullswaggie. Its sole purpose was combustion control. So, if you aren't beating it forget leaded gas and hardened seats. Even if you do, as long as your octane ratings are there, the valve recession rate is so low you'll probably blow it up before recession becomes a problem.
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Old 04-02-2007, 07:40 PM
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valve recession happens , ive had/seen some real bad shape ones- older ones before early 70s, very badly sunken valve heads,

happens

cant say if it was due mostly to not running lead or not, but,,,

good luck
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Old 04-02-2007, 09:45 PM
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61Bone,
Leaded gasoline did in fact exist before WWII. I remember my father buying it. It was called ethyl. Texaco sold "Fire Cheif" unleaded and "Sky Chief" leaded. In the late '50's the big winner was "Golden Esso" 105 octane and I guess really leaded. It must have been special because regular leaded cost 17 cents a gallon and the "Golden Esso" was 21 cents. What a deal. My father owned a garage and we put hard seats, called stellite seats in flat head Fords. Flat heads were prone to cracking at the seat from over heating and the stellite seat was the standard fix.
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Old 04-03-2007, 12:29 PM
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Quote:
Originally Posted by 61bone
Leaded gas didn't exisit before WWII. Everyone ran unleaded. Even into the mid 50s unleaded was common. Unless you are flogging it leaded gas is not necessary in even a 10.5 comp engine. Note that I did not say that you are going to get by with 87 octane unleaded although under easy driving conditions you could. There are many preunleaded cars driving around today on unleaded. I have a couple myself. While I do use an octane booster, I don't use lead replacers. The only thing I can see they do is foul plugs quicker. The "fact" that lead cushions the valves is a bunch of bullswaggie. Its sole purpose was combustion control. So, if you aren't beating it forget leaded gas and hardened seats. Even if you do, as long as your octane ratings are there, the valve recession rate is so low you'll probably blow it up before recession becomes a problem.
Obviously you have never seen valve recession due to absence of lead. I have. Many times.

Leaded gas was around far earlier than WWII.

Interesting read on the whole issue:

http://www.runet.edu/~wkovarik/papers/kettering.html

tom
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Old 04-03-2007, 02:51 PM
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can TEL still be obtained in the USA for "Off Road Purposes" ofcorse
Shane
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Old 04-03-2007, 04:21 PM
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As I understand the story, lead also kicked up the octane level and acted as a lubricant for the valve train assembly. ...One thing, you do know you only have to replace the seats under the exhaust valve ONLY!???
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Old 04-03-2007, 05:01 PM
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Technically, leaded gas was available in the 20s. It is still available today for off road and in avgas. Even these are only using a very small (like a few parts per million) amounts. It was banned in 1995, I believe, for any other use. Running it (tetraethyl lead) in your streetcar puts you in the position of facing a 10 grand fine if caught. Back to the original question. Does valve recession happen? Yes it does in cases of hard usage. For those that have stated they have seen a lot of it, this question. What was the normal usage of the engine? In about 1973 or 4 possibly 5, Hot Rod magazine did a comparison test of leaded versus unleaded and reached the conclusion that there was very little difference between the two as far as recession was concerned. Even the originators of it said originally that it was for antiknock and only at later date added it was good for valve life. Note that it was into the 50s before it came into common usage. Note the post where it was still available as a choice then. The millions of cars built till then must have had a recession heyday but I don't remember hearing about it. Note also that flatty valves were being replaced with hard seats because of overheating not recession My father ran white gas in his 49 Buick till we moved to town in 54. The same gas he ran in his tractors. No lead.
If memory serves, lead vaporizes at about 660 dg. So this lead vapor must be doing the cushioning.
And one more point. The lead replacers you buy to prevent recession today contain no lead.
So If you want to spend the money, go ahead and put in hard seats, add lead replacers, put in a tornado or whatever else floats you boat. Myself? I'm going to continue on using unleaded in the ol studerod T and the 340 hp 327 and when and if recession happens I'll address it with my usual aplomb. Fix it and get going.
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