lead additive

[Jack H.]

Re: lead additive

What was recited above (higher octane beyond what a particular engine requires to run smoothly, without pre-ignition) is true. You're simply thowing $$$ out the exhuast pipes.

When the US converted to lead-free, a number of auto mfgrs were concerned. What would the effects be on earlier car engines built presuming lead was an active fuel additive?

Daimler Benz wrote a white paper for their mechanics and dealers on this with the focus being warranty impact. Among other things, the paper said according to their analysis, once a lead based engine had logged +5K miles on the clock, it'd received ALL of the lead necessary to harden valves/seats for the life of the engine....

[Stuart F.]

Re: lead additive

Joe;

I'm not certain your questions were directed at me or my good friend Stewy down under, but then you did reference my post.

First; I am not able to get to the Mobil station today where I fill the Vette up with premium after "doping" it with Max Lead 2000. Therefore, I can not say what the exact pump "PON" or "RON" figures are.

As to my compression pressures, it's been years since I felt the need or desire to test the engine, but I do have the last test data in my files and I will look for it. My engine has never been apart and has about 44k on the odometer. I did try Duke's feeler gauge check for double head gaskets and could not get a reading that would confirm having them (don't know why, just can't), so I have had to assume mine is a freak with only one gasket.

I used to use about 12oz Max Lead/ tank fill which translates into about 99 Octane (normal load). Lately I have tipped in a bit more, say 18oz which is supposed to provide about 100 to 101 Octane (heavy load).

When I state that it seems to run better, let me preface that my noting that I had been trying to overcome a severe fuel percolation problem during the summer months here in Florida. My efforts began due to the significant amount of gas smell in my attached garage (which the wife complained about alot). I overcame most of that problem with many minor modifications developed using two different AFB's in experiments, and testing primarily with road tests and IR temperature readings taken at specific points, i.e. Carb, intake manifold and exhaust manifolds, thermostat housing, etc.

The main thing I did was to isolate the carb from as much heat as possible, and still remain close to stock in appearance. This resulted in a drop in hot idle temps at the carb of from 35 to 40 degrees. In addition, I experimented with different amounts of the Max Lead additive and found that the more I used, the lower my exhaust manifold temps were at the junctures of the manifold to the heads (each port), some 10 to 20 degrees.

In driveability, I was able to iliminate hesitation and stumble, as well as noticeable engine heat up while idling in traffic. Yes, under these circumstances, I did see temperature rise in the area of + 10 or +20 degrees, but gone was the usual hesitation, stumble or stalling of days past under these conditions. The response was right there. In all honesty, my 63 has never run better in the 46+ years that I have owned it. Some day I may gather up all my test notes and put together an article - before I forget everthing.

Stu Fox

[Michael M.]

Re: lead additive

The newer engines of today do not need much lead because of their lower compression. The engines from the 60's with 11:1 compression need lead in the gas if you want to keep your timing advanced. I do not use a lead additive but I do use 100 octane low lead aviation gas mixed with Marvel Mystery Oil for a top engine lubricant.

[Dale S.]

Re: lead additive

If you really want you Corvette to run hard, get rid of all the snake oils and buy some VP C-25. I used to save the C-25 VP Pro Stock gas in separate 5 gallon containers and hauled them home. I used to put it in my base engine 1967 and you could hear the difference in the exhaust note at idle. The exhaust gasses would make your eyes water. Rocket Fuels (Old Union 76) also make a equivalent called "Pro Stock". Sunoco make a "Sunoco Maxi". All are very good. Just my opinion. Dale

[Michael W.]

Re: lead additive

The newer engines of today do not need much lead because of their lower compression. The engines from the 60's with 11:1 compression need lead in the gas if you want to keep your timing advanced. I do not use a lead additive but I do use 100 octane low lead aviation gas mixed with Marvel Mystery Oil for a top engine lubricant.

Must disagree. My 2003 vintage daily driver has an 11:1 compression ratio and runs just fine at full factory advance on 91 octane.

'Lead' was a cheap but very nasty way of increasing octane ratings of gasoline back in the bad old days. Modern gasolines achieve the same ratings without the use of lead. There's a good reason that all the snake oil additives being promoted here and elsewhere are not legal for street use.

Offered purely as a counterpoint.

[John H.]

Re: lead additive

I thought that the lead was necessary in older (pre-unleaded gas) engines for valve lubrication and wear purposes.

Only if it's in a boat or if you're towing a trailer at 100 mph all day long (constant high power settings); valve seat recession in our classics in normal driving is a myth, although the marketers of all the "miracle elixirs" would have you believe your engine will surely disintegrate in a ball of flame and a hail of shrapnel unless you use their product religiously.

[Joe C.]

Re: lead additive

Must disagree. My 2003 vintage daily driver has an 11:1 compression ratio and runs just fine at full factory advance on 91 octane.

'Lead' was a cheap but very nasty way of increasing octane ratings of gasoline back in the bad old days. Modern gasolines achieve the same ratings without the use of lead. There's a good reason that all the snake oil additives being promoted here and elsewhere are not legal for street use.

Offered purely as a counterpoint.

Additives using MML or Toluene as the active ingredient do not work well to thwart detonation.
TEL is much more effective.

[Duke W.]

Re: lead additive

The newer engines of today do not need much lead because of their lower compression. The engines from the 60's with 11:1 compression need lead in the gas if you want to keep your timing advanced. I do not use a lead additive but I do use 100 octane low lead aviation gas mixed with Marvel Mystery Oil for a top engine lubricant.

Uh... do you know what the compression ratios are of current Corvette engines?

Duke

[Michael W.]

Re: lead additive

Additives using MML or Toluene as the active ingredient do not work well to thwart detonation.
TEL is much more effective.

True- but the point still remains that if an engine does not suffer from pre-ignition on pump gas, there's no need to add lead or any other miracle potion.

[Michael W.]

Re: lead additive

your engine will surely disintegrate in a ball of flame and a hail of shrapnel unless you use their product religiously.

Well, I've learned something. I always thought it was one or the other. Never thought it was both.

[Joe C.]

Re: lead additive

Joe;

I'm not certain your questions were directed at me or my good friend Stewy down under, but then you did reference my post.

First; I am not able to get to the Mobil station today where I fill the Vette up with premium after "doping" it with Max Lead 2000. Therefore, I can not say what the exact pump "PON" or "RON" figures are.

As to my compression pressures, it's been years since I felt the need or desire to test the engine, but I do have the last test data in my files and I will look for it. My engine has never been apart and has about 44k on the odometer. I did try Duke's feeler gauge check for double head gaskets and could not get a reading that would confirm having them (don't know why, just can't), so I have had to assume mine is a freak with only one gasket.

I used to use about 12oz Max Lead/ tank fill which translates into about 99 Octane (normal load). Lately I have tipped in a bit more, say 18oz which is supposed to provide about 100 to 101 Octane (heavy load).

When I state that it seems to run better, let me preface that my noting that I had been trying to overcome a severe fuel percolation problem during the summer months here in Florida. My efforts began due to the significant amount of gas smell in my attached garage (which the wife complained about alot). I overcame most of that problem with many minor modifications developed using two different AFB's in experiments, and testing primarily with road tests and IR temperature readings taken at specific points, i.e. Carb, intake manifold and exhaust manifolds, thermostat housing, etc.

The main thing I did was to isolate the carb from as much heat as possible, and still remain close to stock in appearance. This resulted in a drop in hot idle temps at the carb of from 35 to 40 degrees. In addition, I experimented with different amounts of the Max Lead additive and found that the more I used, the lower my exhaust manifold temps were at the junctures of the manifold to the heads (each port), some 10 to 20 degrees.

In driveability, I was able to iliminate hesitation and stumble, as well as noticeable engine heat up while idling in traffic. Yes, under these circumstances, I did see temperature rise in the area of + 10 or +20 degrees, but gone was the usual hesitation, stumble or stalling of days past under these conditions. The response was right there. In all honesty, my 63 has never run better in the 46+ years that I have owned it. Some day I may gather up all my test notes and put together an article - before I forget everthing.

Stu Fox

Stu,

I see that you live in Florida, so your local fuel octane levels (PON rating) is the same as mine in NJ: 93.

Joe

[Joe C.]

Re: lead additive

True- but the point still remains that if an engine does not suffer from pre-ignition on pump gas, there's no need to add lead or any other miracle potion.

Of course!
An engine produces the most torque when it is running with its highest cylinder pressure. This means that an engine produces peak torque when it is running at the point just prior to "incipient" detonation, and only a variable and truly optimized spark advance "map" can provide this.
It is virtually impossible to set up a spark advance "map" which can provide this using mechanical controls. ECM/PCM management is the only way.............
Peak cylinder pressure, and at what point in the cycle it occurs, is determined principally by combustion chamber design (which determines burn rate), spark timing (which initiates the burn, if octane rating is sufficient), and fuel octane rating (which determines ignition temperature).

[Joe L.]

Re: lead additive

Where can I get a lead additive for my 62 327? I use to get it at discount auto but they no longer carry it in my area. Joe

Joe-----


As everyone else has mentioned, you do not need any more octane than it takes to keep you out of significant pre-ignition. If pump premium (91, 92, or 93 octane, depending where you live) accomplishes this, that's all you need as far as octane goes. Period. In fact, if the car runs ok without significant pre-ignition on premium, then try mid-grade. That may be enough and, if it is, you're throwing away money by buying a higher octane. Period.

As far as exhaust valve seat problems go, you don't need any lead unless you operate under severe conditions (and you won't be). In fact, for many other reasons, you're better off WITHOUT lead in the fuel. By adding lead, you're potentially creating more problems than you're solving, especially since you really aren't solving any real problem, at all. However, if you want to use something to make you feel better, use Alemite CD-2 lead substitute. This product contains "Powershield", manufactured by the Lubrizol Corporation. It's quite concentrated so you only need to use 1 ounce per 10 gallons. This makes it quite convenient to carry with you and use when you fill up. As I say, you don't really need this but if it makes you feel better, it's relative cheap, easy to use, and it won't cause any other problems.

John Lingenfelter once said that unleaded gas was the best thing that ever happened for performance engines. He was right.

[Joseph P.]

Re: lead additive

Thanks again for all the additional info. I have learned a lot today. I have always believed the myth about lead. It's always good to get the correct information from independent people. I am new to this forum and to this hobby. I can tell it's going to be fun.

[Duke W.]

Re: lead additive

Most in this thread seem to lost track of the fact than detonation and preignition are NOT the same thing, but one can lead to the other.

"Octane number" is a measure of a fuel's resistance to DETONATION.

Duke