Leaded fuel additive

[jlobenberg]

Does anyone know how often I should run a leaded fuel additive in a 1969 350?

 

[Vettehead Mikey]

Does anyone know how often I should run a leaded fuel additive in a 1969 350?

That's simple. Never. There's absolutely no need not to mention that additives that actually contain lead (TEL) are illegal for street use..

In the 40+ years that unleaded has been used in Corvettes of all vintages, not one engine has been damaged as a result. The myths just won't die though.

 

[kpic]

Mikey is spot on.
I helped a bud rebuild his 69. It has run unleaded for decades and its valve seats look about the same as any valve seat with over 100K on them.

If you really want to use an additive that replaces lead:
http://www.classicrallyclub.com.au/docs/Tips_lead_and_substitutes_facts.pdf

 

[Vettehead Mikey]

I've read that article before and wonder if some of the points it tries to make do more harm that good by just adding to the myths and misinformation.

It stresses that valve seat recession (VSR) is a certainty and that damage is inevitable. The article was written in the UK before lead was removed from their fuel. Much like in North America, and using our Corvettes as a good example, the wild doom and gloom predictions were proven to be grossly exaggerated.

The article goes on to mix VSR with the subject of detonation/fuel octane rating- as though one is directly related with the other. They're not of course.

 

[stevolwevol]

That's simple. Never. There's absolutely no need not to mention that additives that actually contain lead (TEL) are illegal for street use..

In the 40+ years that unleaded has been used in Corvettes of all vintages, not one engine has been damaged as a result. The myths just won't die though.

Well Vettehead, I would just wait till there aren't any cops looking if I needed it.

A few years back I owned a 69 pickup, and i added a lead substitute concentrate. It said it was for "off street use only", but I made sure I didn't add it in front of the police. I still don't actually know if it did any good, I just used it. I believe it was "CD 2" or something like that.

 

[Vettehead Mikey]

Well Vettehead, I would just wait till there aren't any cops looking if I needed it.

A few years back I owned a 69 pickup, and i added a lead substitute concentrate. It said it was for "off street use only", but I made sure I didn't add it in front of the police. I still don't actually know if it did any good, I just used it. I believe it was "CD 2" or something like that.

So why would you use it, legal or not?

 

[stevolwevol]

So why would you use it, legal or not?

This was over 10 years ago, but I was told that unleaded gas was hard on the valves/seats, and a lead substitute would help this. It was a 360 ford engine, and I didn't have a engine ping problem, but I was still concerned about the valve issue, so I used it. It was running well when I sold it, but I don't know if ever helped. Maybe it was just aftermarket snake oil, but it was cheap and easy to use.

 

[kpic]

I've read that article before and wonder if some of the points it tries to make do more harm that good by just adding to the myths and misinformation.

It stresses that valve seat recession (VSR) is a certainty and that damage is inevitable. The article was written in the UK before lead was removed from their fuel. Much like in North America, and using our Corvettes as a good example, the wild doom and gloom predictions were proven to be grossly exaggerated.

The article goes on to mix VSR with the subject of detonation/fuel octane rating- as though one is directly related with the other. They're not of course.

Ditto on some of the recommendations have a potential risk of doing more harm than good. Using the correct chemicals, anyone can "dope" the oil in a manual transmission. Engines are quite a different subject.

Lead was added to gasoline in the 1920s to raise octane. Lead was also a lubricant.

One thing I don't buy:

Before the development and introduction of lead to fuel, engines were successfully run without lead, albeit at low compression ratios which gave low power and low fuel economy. As engines of the period were not
highly stressed valve seat recession did not appear to be a major problem

http://www.classicrallyclub.com.au/docs/Tips_lead_and_substitutes_facts.pdf

Lead was added to gasoline in the 1920s to reduce engine knock and enable engineers to design cars with higher compression in the cylinders, permitting greater power and efficiency.

Hidden History of Leaded Gasoline Reveals Industry Conspiracy to Conceal Dangers - Lethal Product Still Marketed Throughout World

So as lead was first added to gasoline in the 1920s. Where did the first article find the low power, low compression engines? There weren't high compression engines for quite a few decades after the 1920s. It seems they need to pay some attention to the CR of engines of the 20s, 30s, 40s and 50s.

I've rebuilt cars and motorcycles and not just mine. To date, I haven't seen anything. In all fairness, lead was a combustion chamber lubricant in an IC engine. Same as anyone, I've seen lead deposits on the valve seats. Nor have I heard of anyone who had to replace exhaust valve seats for a reason.

To be quite honest, I haven't seen VSR myself. There are a lot of decent mechanics on this board. Maybe some have seen it and I'd believe them.

 

[Vettehead Mikey]

To be quite honest, I haven't seen VSR myself. There are a lot of decent mechanics on this board. Maybe some have seen it and I'd believe them.

It is a factor on some vehicles. I know that it gives my buddies with old Triumph/MG/Sunbeam types a hard time. I had a Norton Commando that suffered greatly with unleaded fuel.

The key is understanding that, aside from poor quality materials, VSR is tied directly to 'time at temperature', meaning that if the valve seat is run hot enough for long enough, the specific conditions for VSR may be present. The process of microwelding reference is your article is spot on in that respect.

A Corvette accelerating through the gears might produce the required temperatures, but not for a long enough period of time. A Corvette running at obscene speeds might satisfy the time requirement, but the engine is just loafing in terms of power output and therefore heat produced.

A 70's vintage station wagon packed with the family and pulling a travel trailer up long mountain grades is a different animal.

 

[kpic]

It is a factor on some vehicles. I know that it gives my buddies with old Triumph/MG/Sunbeam types a hard time. I had a Norton Commando that suffered greatly with unleaded fuel.

The key is understanding that, aside from poor quality materials, VSR is tied directly to 'time at temperature', meaning that if the valve seat is run hot enough for long enough, the specific conditions for VSR may be present. The process of microwelding reference is your article is spot on in that respect.

A Corvette accelerating through the gears might produce the required temperatures, but not for a long enough period of time. A Corvette running at obscene speeds might satisfy the time requirement, but the engine is just loafing in terms of power output and therefore heat produced.

A 70's vintage station wagon packed with the family and pulling a travel trailer up long mountain grades is a different animal.

Micro welding to those hot spots on valve seats is a fact. Using a high powered microscope shows them. With old time leaded gas, a spectrum analyzer would identify the material deposits on the exhaust seat as lead. The eyes could see the deposits because the color was different.

The factor in some vehicles would be based on the materials the OEM chose to make the exhaust seats. A bit greater percentage of this or that can make all the difference.
The problem, us everyday people have no clue what those differences are unless we worked in the design group and remembered what was in that little material rectangle on the drawing.
As one who worked in design engineering for 45 years, I can promise there is no chance of that happening.

Everything is tied to time at temperature and duration of the load. That station wagon towing a wet weight camper up a grade is in a bad spot.
I lack the knowledge of heat and duration for a Corvette running wide open to have an opinion. Who runs an older Corvette at obscene speeds for a long time? Yes I can; however as I want to keep my license, I sure don't.
The problem with engineers is if you ask a question, they answer it. What they don't do is answer it completely because the average person isn't interested in all the details the real answer entails.

Kudos on the Norton Commando, it is one of the motorcycles I always liked a lot and never owned. With a Norton, it's time to swap the seats.
My current ride is a 1980 Harley Super Glide. S&S 4-5/8 stroke and Axtel big bore barrels. I haven't seen any issues with exhaust valve seats. As all I do is cruise, there is the reason why I don't see it.

 

[Hib Halverson]

That's simple. Never. There's absolutely no need not to mention that additives that actually contain lead (TEL) are illegal for street use..

In the 40+ years that unleaded has been used in Corvettes of all vintages, not one engine has been damaged as a result. The myths just won't die though.

Can you post some evidence to support that last statement?

 

[Vettehead Mikey]

Can you post some evidence to support that last statement?

Since I've not personally seen every Corvette engine that was built, there is no absolute proof. Given that unleaded fuel has been around for over 40 years I suppose that this might be a long enough time period for some sort of evidence or trend to emerge given the millions of SBC and BBC built. I can find no trace other than on heavy duty applications where the time at temperature requirement is met. The boating guys can give you all the sordid details.

Most responsible engine shops now refrain from installing hardened seats primarily because they're not needed but also from the unacceptable failure rate where a perfectly good head is ruined by accidentally machining into a cooling passage.

 

[jlobenberg]

Thanks All

Thanks to everyone for the valuable info. I won't waist my time on lead additive.

 

[Hib Halverson]

Since I've not personally seen every Corvette engine that was built, there is no absolute proof. Given that unleaded fuel has been around for over 40 years I suppose that this might be a long enough time period for some sort of evidence or trend to emerge given the millions of SBC and BBC built. I can find no trace other than on heavy duty applications where the time at temperature requirement is met. The boating guys can give you all the sordid details.

I'm not intersted in anecdotal accounts from "boating guys".

Can you supply any test data or other credible information supporting your statement which imples that valve seat recession is a myth. Come on "Vettehead Mikey", you can't make blanket statements like that without some evidence.

Most responsible engine shops now refrain from installing hardened seats primarily because they're not needed but also from the unacceptable failure rate where a perfectly good head is ruined by accidentally machining into a cooling passage.

Of course you are ignoring the fact that every Corvette engine since 1987 has hard valve seats.

 

[Vettehead Mikey]

I'm not intersted in anecdotal accounts from "boating guys".

Can you supply any test data or other credible information supporting your statement which imples that valve seat recession is a myth. Come on "Vettehead Mikey", you can't make blanket statements like that without some evidence.

The boating guys and RV owners will supply all sorts of data showing that VSR doesexist in their world. Again- time at temperature. The Corvette community does not appear to be able to follow suit.

Of course you are ignoring the fact that every Corvette engine since 1987 has hard valve seats.

Ummm no I'm not, and it was late 1970/early 1971, not 1987. GM adopted induction hardened valve seats in that time frame in preparation for the advent of unleaded fuels. It was deemed to be more cost effective to do all heads irrespective of end purpose (heavy duty vs regular duty application swhere VSR woud not be seen) rather then create separate part numbers.

 

[stevolwevol]

The boating guys and RV owners will supply all sorts of data showing that VSR doesexist in their world. Again- time at temperature. The Corvette community does not appear to be able to follow suit.



Ummm no I'm not, and it was late 1970/early 1971, not 1987. GM adopted induction hardened valve seats in that time frame in preparation for the advent of unleaded fuels. It was deemed to be more cost effective to do all heads irrespective of end purpose (heavy duty vs regular duty application swhere VSR woud not be seen) rather then create separate part numbers.

Vettehead, you are saying that back in 70-71 GM hardened valve seats because they were anticipating the use of unleaded fuel in the near future, so these engines would be compatible with unleaded fuel?

 

[Vettehead Mikey]

Vettehead, you are saying that back in 70-71 GM hardened valve seats because they were anticipating the use of unleaded fuel in the near future, so these engines would be compatible with unleaded fuel?

Exactly. VSR (or lack thereof) was not an unexpected consequence.

 

[kpic]

Induction hardened process is heating the base material to about 1200F, then quenched. Although it is an expensive process.
Older seats were flame hardened.

The depth of induction hardening can be from ,5 to 6mm or .02 to .24".
http://image.slidesharecdn.com/heat...eatment-of-steels-ii-29-638.jpg?cb=1447132878

How come my stock heads never had this issue?

The valve seats on stock heads as they come from the factory are induction hardened. This is a process where the valve seat surface is case hardened by applying a heated coil to the seat for some time. The result is a hardened surface in the seat area that is resistant to VSR. Most experts believe that typically, the depth of the induction hardened material runs approximately 0.030" deep. Fortunately for us, we've recently discovered that the General has done a little better on our heads. When one decides that they will fit oversized exhaust valves in their heads, one must be careful because some this hardened area will have to be cut. If the valve is large enough and the cut is deep enough, this hardened material may be completely removed.
http://www.intense-racing.com/VSR/VSR.html

According to the above the case depth is .03" or ,76mm. Why so little when the process is capable of more? I don't know.

The answer to why so many cylinder heads do not show any sign of VSR could easily be they are stock. Or better said, they never had enough valve jobs to remove the ~.03"/,76mm of induction hardening.

It appears potentially everyone is correct.