unleaded Fuel
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As long as you have hardened valve seats you'll be fine.
I'd read this information and make your own conclusion. Only you know how often and hard you drive your car.
http://www.chevron.com/products/prodserv/fuels/bulletin/unld-gas/
http://www.chevron.com/products/prodserv/fuels/bulletin/unld-gas/
The engine had a rebuild in 2001 but i dont know if they hardened the valve seats.I was adding a Lead substitute that you can get at any auto center then was told dont bother with it so i stop it.I guess it cant harm by adding it just in case or can it?
Thanks thats a good read..
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I've been jacking with these old Chevys for 45+yrs, and here is the conclusion from my personal observations.
On OLDER engines, which have heads that DO NOT have hardened exhaust seats (intake seats are a non-issue), valve seat recession and valve head wear CAN occur with the use of UNleaded gasoline.
When the introduction of unleaded gas began, and leaded gas started going away, there was a BIG DEAL made of excessive valve/valve seat deterioration. EVERYONE jumped on the band wagon to sell lead additives and/or machine shops heavily promoted installing hardened valve seats in older heads. I have had hardened exhaust seats installed in MANY heads since.
Should this have been done????????????? Good question! The answer is DIRECTLY related to the use and severity of loading placed on each individual engine. If, in the case of special interest, classic, low usage and antique cars, as a result of my experience with engines in many of these types of cars, these cars are not typically used as extended use and high loading on the engines, it is not prudent to have hardened exhaust seats added to older heads (Whew, that was a long sentence!). Neither is it of significant benefit to add a lead additive to the fuel system.
I believe that in the beginning, it was genuinely thought that unleaded gas in the older engines would eventually become detrimental to the valves/valve seats. But, over many years------------------ESPECIALLY IN THE OLDER, LOW USEAGE CARS-----------------this just hasn't been a significant, if any at all, problem. I have one car, with a 350 engine that I built 31yrs ago and have NEVER pulled a head, which I drive EVERYDAY to work, 45mi roundtrip, that is still running great with zero indication of significant valve leakage (the heads are 66 versions and no hard seats)! Because of the initial concern about valve recession in the early 70s, which convinced most people that some kind of remedy (installing hard seats or adding a lead substitute) was needed, this concern has been unnecessarly propogated by those who profit from the original concerns (lead additive sellers and machine shops). What I am doing now when rebuilding an engine is simply buying/installing stainless valves for the heads along with a good rebuild of the heads.
Sooooooooooooooooo, bottom line, on low useage engines, such as in MOST of our Chevelles, when you do an engine rebuild, just have a good rebuild of the heads done and install stainless valves and go on down the road.
Below, I have copied and pasted a portion of the link posted above. I think it is 100% on the money!
Passenger Cars and Light-Duty Trucks:
Based on an extensive survey of the published literature, fleet operators, engine rebuilders, and manufacturers, we conclude that all typical passenger car and light-duty truck engines (representing 94% of U.S. gasoline consumption) are safe from valve recession when operated on unleaded gasoline. They are either equipped with induction hardened valve seats or subjected to service too mild to cause problems. The problem can only occur in older engines when operating under sustained high speeds and loads.
Vintage Vehicles:
Antique cars are typically exposed to such light service that they are not expected to have any valve seat problems. In fact, they stand to benefit overall from a reduction in exhaust system corrosion and oil contamination.
On OLDER engines, which have heads that DO NOT have hardened exhaust seats (intake seats are a non-issue), valve seat recession and valve head wear CAN occur with the use of UNleaded gasoline.
When the introduction of unleaded gas began, and leaded gas started going away, there was a BIG DEAL made of excessive valve/valve seat deterioration. EVERYONE jumped on the band wagon to sell lead additives and/or machine shops heavily promoted installing hardened valve seats in older heads. I have had hardened exhaust seats installed in MANY heads since.
Should this have been done????????????? Good question! The answer is DIRECTLY related to the use and severity of loading placed on each individual engine. If, in the case of special interest, classic, low usage and antique cars, as a result of my experience with engines in many of these types of cars, these cars are not typically used as extended use and high loading on the engines, it is not prudent to have hardened exhaust seats added to older heads (Whew, that was a long sentence!). Neither is it of significant benefit to add a lead additive to the fuel system. I believe that in the beginning, it was genuinely thought that unleaded gas in the older engines would eventually become detrimental to the valves/valve seats. But, over many years------------------ESPECIALLY IN THE OLDER, LOW USEAGE CARS-----------------this just hasn't been a significant, if any at all, problem. I have one car, with a 350 engine that I built 31yrs ago and have NEVER pulled a head, which I drive EVERYDAY to work, 45mi roundtrip, that is still running great with zero indication of significant valve leakage (the heads are 66 versions and no hard seats)! Because of the initial concern about valve recession in the early 70s, which convinced most people that some kind of remedy (installing hard seats or adding a lead substitute) was needed, this concern has been unnecessarly propogated by those who profit from the original concerns (lead additive sellers and machine shops). What I am doing now when rebuilding an engine is simply buying/installing stainless valves for the heads along with a good rebuild of the heads.
Sooooooooooooooooo, bottom line, on low useage engines, such as in MOST of our Chevelles, when you do an engine rebuild, just have a good rebuild of the heads done and install stainless valves and go on down the road.
Below, I have copied and pasted a portion of the link posted above. I think it is 100% on the money!
Passenger Cars and Light-Duty Trucks:
Based on an extensive survey of the published literature, fleet operators, engine rebuilders, and manufacturers, we conclude that all typical passenger car and light-duty truck engines (representing 94% of U.S. gasoline consumption) are safe from valve recession when operated on unleaded gasoline. They are either equipped with induction hardened valve seats or subjected to service too mild to cause problems. The problem can only occur in older engines when operating under sustained high speeds and loads.
Vintage Vehicles:
Antique cars are typically exposed to such light service that they are not expected to have any valve seat problems. In fact, they stand to benefit overall from a reduction in exhaust system corrosion and oil contamination.
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22,931 Posts
There's a GM Tech Service bulletin copied in the latest issue of Chevelle World on this subject...
When referring to pre 1971, it all depends on the casting. Some were made of harder materials.
The Cadillac 472/500 cyl heads were made of a harder metal composition. I think they may have more nickel or something. You hardly ever see the exhaust seats worn down on these heads. And the guides usually show minimal wear at 100,000+ miles also.
I've torn down hundreds of virgin cylinder heads. And I've rebuilt hundreds. 95% of the cast iron heads needing a rebuild today should have hardened exhaust seats installed. It doesn't matter what kind of driving you do. And for those of you that don't know about seats, there are different qualities of seats, meant for different applications. Some are softer than others. Some are very hard. Us guys in the machine shop business know this first hand as we grind them, day in and day out.
Most cast iron heads 1972 and newer will have induction hardened exhaust seats. I've seen these go away regularly. One set of heads comes to mind. This guy has these 70 Blazer 350 heads rebuilt some 10-12 years ago and rarely drove it, and within 20,000 miles the engine was running so badly, he tore it down again. He brought me the heads and the seats were so far gone that I wasn't sure if I could save them. The only way to know is to bore for the seat and see if you get a clean bore. You can go slightly oversized, but you run the risk of hitting water if you go too big. All castings are different and some have thin casting.
In summary, if cast iron heads didn't need hardened seats, then GM would not have begun putting them in their heads around 2000.
My guess would be that all of the HD trucks GM sells today with cast iron heads will have hardened seats installed. I haven't seen any past about 2002, so I can't say from experience on those. But I began to see the false seats around 2000.
It should also be noted that ANY valve you buy today will be made of stainless steel. What's important is a good chrome stem, and a hardened tip.
The Cadillac 472/500 cyl heads were made of a harder metal composition. I think they may have more nickel or something. You hardly ever see the exhaust seats worn down on these heads. And the guides usually show minimal wear at 100,000+ miles also.
I've torn down hundreds of virgin cylinder heads. And I've rebuilt hundreds. 95% of the cast iron heads needing a rebuild today should have hardened exhaust seats installed. It doesn't matter what kind of driving you do. And for those of you that don't know about seats, there are different qualities of seats, meant for different applications. Some are softer than others. Some are very hard. Us guys in the machine shop business know this first hand as we grind them, day in and day out.
Most cast iron heads 1972 and newer will have induction hardened exhaust seats. I've seen these go away regularly. One set of heads comes to mind. This guy has these 70 Blazer 350 heads rebuilt some 10-12 years ago and rarely drove it, and within 20,000 miles the engine was running so badly, he tore it down again. He brought me the heads and the seats were so far gone that I wasn't sure if I could save them. The only way to know is to bore for the seat and see if you get a clean bore. You can go slightly oversized, but you run the risk of hitting water if you go too big. All castings are different and some have thin casting.
In summary, if cast iron heads didn't need hardened seats, then GM would not have begun putting them in their heads around 2000.
My guess would be that all of the HD trucks GM sells today with cast iron heads will have hardened seats installed. I haven't seen any past about 2002, so I can't say from experience on those. But I began to see the false seats around 2000.
It should also be noted that ANY valve you buy today will be made of stainless steel. What's important is a good chrome stem, and a hardened tip.
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