Hardened Vave Seats

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Mar 7, 2002 | 11:23 AM

bungoo2u

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Hardened Vave Seats

I have a set of cast iron camel hump heads. Why is it reccommended to install hardened valve seats on the exhaust valves? What will happen if I don't use hardened valve seats?
Thanks

Mar 7, 2002 | 11:53 AM

CFI-EFI

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From: The Top of Utah

Re: Hardened Vave Seats (bungoo2u)

In the olden days gasoline contained lead as an additive to increase the octane levels. Lead acted as a "cushion" between the valves and the valve seats. With today's, low lead/unleaded fuels, hardened valve seats are necessary in order for then to live. Most, if not all, production engines built after about 1970 have hardened seals and better valves.

Mar 7, 2002 | 12:02 PM

bungoo2u

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Re: Hardened Vave Seats (CFI-EFI)

thanks for your reply,
what will happen if I don't use the hardened seats. What if I use a lead additive every so often, would it help. Reason, the machine shop quoted me around $500 to install the seats. Not worth putting in the money in an ancient head.

Mar 7, 2002 | 06:20 PM

clem zahrobsky

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Re: Hardened Vave Seats (bungoo2u)

save your money,because unless you race or pull a trailer with the car the seats will last a lifetime. amoco(white) gas has been lead free since the 30s and it caused no problems even back then.

Mar 7, 2002 | 07:05 PM

CFI-EFI

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Re: Hardened Vave Seats (bungoo2u)

I disagree with Clem, But I have no hard facts. My information comes mostly by word of mouth and "lore". I can't claim to be an authority on the subject. I would call the manufacturers of the lead additive, and question the machine shop in more detail. $500.00 seems like more than enough to have to spend. My information, is that the valve job and/or seats would have a significantly shortened life. But, I remind you that my imformation is largely anecdotal and not PROVEN, even to me. Keep asking, and good luck.

PS. Even though I can't back up my statements with fact, I am NOT just shooting from the hip, here. I have read articles on the subject, and seen pictures in trade magazines showing the damage caused by insufficent lead in the fuel. And to clarify further, I'm not saying that there would be any kind of catistropic failure, just a shorter life. If I can be proven wrong...so be it. I doubt that Detroit hardened seats and changed valves because they had some extra cash laying around.

[Modified by CFI-EFI, 5:16 PM 3/7/2002]

Mar 7, 2002 | 11:57 PM

DON M

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Re: Hardened Vave Seats (bungoo2u)

Some of the later cast iron heads had induction hardened seats from the factory. GM saw this comming many years ago. This explains why many older cars survived the change to unleaded. The first valve job will remove the hardened metal. New seats are in order with todays gas.

Mar 8, 2002 | 09:56 AM

norvalwilhelm

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From: Waterloo ontario Canada

Re: Hardened Vave Seats (clem zahrobsky)

I agree with Clem. Unless you are pulling a trailer you will not have problems with normal valve seats. I have a 69 LS6 motor without the hardened valve seats. I have done at least 2 valve jobs but not because of a problem. The last time I wanted to go with the hardened seats. Money did not matter and the machine shop asked WHY? My seats were in no way sunk after all those years. I wouldn't waste the money or worry about it. I did install larger 2.25 valves and 1.90 exhausts but not because of a problem.