CD-2 Lead Substitute use okay???

How old is "old"? Since 1972, all motor vehicle engines sold in the US have been required to be mechanically tolerant of no-lead gasoline.

And, largely, to no consequence for old vehicles.

With an unhardened (pre-1972) exhaust valve and seat, the valve and seat can micro-weld to each other if they get hot enough. Lead acts as a buffer to prevent this happening. The important thing is that exhaust valve and seat recession ONLY takes place when the valve gets hot enough to undergo localised welding. Then, when the valve opens next, the metal pulls apart like taffy. This roughens the meeting surfaces, and they become quite abrasive. The pounding/turning of a valve with such "pulled" metal on it creates a nice grinding wheel effect on the seat. In addition, the roughened surfaces no longer seal against each other properly, which eventually allows still-burning combustion gases to flow through the "closed" valve, causing a blowtorch effect on the poor valve and depriving it of any prayer of a chance to cool while it's on the seat. The blowtorch effect rapidly deteriorates the seal further, snowballing the seat recession.

The main thing to remember is that this bad stuff *cannot* happen If the valve never reaches the crucial temperature. Whether the valve reaches the crucial temperature depends mainly on how the car is driven and used (Towing, drag racing or pedal-on-the-floor hauling WILL heat the valves--driving down the highway at a constant 70 won't, and neither will hopping from traffic light to traffic light in the city or running down to the local grocery for a carton of ice cream.) Other factors in the margin of safety include the size of the exhaust valve, its material, and the efficiency of valve seat cooling in that particular engine design.

Very *VERY* little lead is required to prevent the localised welding and "taffy pull apart" effect that leads to the abrasive surface which, through incidental or positive rotation of the valve, eventually grinds-down an unhardened seat. I'll emphasize that again: VERY LITTLE LEAD. The remainder was in the fuel as an octane booster, that's all. It was widely used because it was a very cheap and very effective octane booster. When unleaded fuels were first widely introduced (which introduction was brought about by legislation) , there was generally only one grade of unleaded available, and the octane was *quite* low--less than that of leaded regular.

We all know that when you use a fuel of insufficient octane, your engine pings (detonation, pinking, pinging, spark knock--call it what you will.) This phenomenon creates *tremendous* heat in the combustion chamber--certainly enough heat to push the exhaust valves to the crucial temperature. Because for quite a while only unleaded fuel of subregular octane was available, plenty of people experienced these effects from using unleaded. While a fraction of those engines that suffered under this low-octane unleaded really *DID* need the lead (high load and/or high-RPM engines), the vast majority of the failures were due to the low octane increasing combustion chamber temperatures (see above). And so the myth was born that old cars' engines "WILL DIE" if run on unleaded.

These days we have universal availability of high-octane unleaded fuels, which obviate the insufficient-octane cause of valve heating and subsequent localized welding.

if you have an old car that is a low-stress application , used in daily-driver service, then you need have no qualms about using whichever octane grade of lead-free fuel your car runs well on and drive it for a Loooooooonnnnnng time with nary a valve or seat problem. Many domestic 6 and 8 cylinder engines fall into this category in normal daily driving service. The way to eliminate even the *possibility* of valve heating causing localized welding and subsequent seat recession is to install hardened exhaust valve seat inserts and exhaust valves of upgraded material (typically 21-4N stainless instead of 21-2N). This is utterly standard practice in the rebuilding of cylinder heads, and has been for years.

Hard seats and valves are readily available for just about anything you want to put them in. It's a very common operation and a competent machine shop can handle it. But the main thing here is that there's absolutely no reason to tear into the engine solely to install hard seats. There is no collateral damage from seat recession. Drive and enjoy! You likely won't experience any problems for a LONG time, if ever. If you ever do, have a head job done.

The additives available on shelves vary widely in what they do. Some of them use a sodium salt and claim to duplicate the buffer effect of lead. Some of them use "MMT" (methylcyclopentadienyl manganese tricarbonyl), which is not a very nice substance at all and is of questionable benefit in buffering exhaust valves. Regardless of whether or not any human-health or environmental risk is posed by MMT, the stuff causes hard red deposits on your spark plugs that will cause you to need to replace them more often. Other additives are simply octane boosters of varying effectiveness and varying side effects.

It's worth noting that on the East Coast of the US, Amoco marketed unleaded high-octane gasoline for *decades* before the EPA decided to "unlead" the country's fuel by regulation. That Amoco high-test unleaded was widely regarded as quite a fine fuel indeed.

Another poster in this thread claimed that lead-substitute additives will "give you peace of mind". That's about all the good they'll do. They're expensive, messy to work with, often hazardous to store in your trunk, are a hassle, and--in the vast majority of cars driven on the street--just aren't necessary.

Of greater concern to you should be the growing use of "reformulated" and "oxygenated" fuels in many areas of the country, either year round or seasonally. These fuels can attack and degrade some parts of your fuel system and can cause driveability problems. There's a lot you can do for very little money and effort to proof your old car against these new fuel formulations.

DS

substitutes are fine, but i think you should find out if you need the lead at all...

if the lead substitute was added for an octane boost to avoid pinging, you just need to use high enough octane unleaded to stop it from pinging and/or use a less agressive timing advance. pinging (preignition) can break ring lands and rings. that would be bad...

if it was used to provide lubrication for non-hardened valve seats, using unleaded will cause increased wear on the valve seats, but this will only show up over a long period of time. if it's just a weekend cruiser, you won't run up enough miles to tell the difference. if it's your daily driver and you plan on keeping it for a while, you should a) run the substitute, or b) install hardened valve seats.

mstrhappygolucky wrote:

I use a lead substitute all the time in my old cars. Buy it by the gallon, its cheaper.

mike hunt

mstrhappygolucky wrote:

We use it in our old V-8 Ford powered inboard boat. Still screams better than new.

1/2 oz. to 10 gallons... it goes a long way in a boat only used 45-50 hrs. per year.

Rob

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The problem with this kind of "I use it and my engine runs great" report is that...well, forgive me stepping on your feelings, Rob, but they're meaningless. If you said "We have two old V8 Ford powered inboard boats...we use this additive on one of them and not on the other, and the one without additives has had to have two valve jobs that haven't been needed on the one with the additive", that would mean something. But your "I use it and my engine runs great" is exactly the same as if I were to say "I swing my left arm in a circle for fifteen minutes every day -- it works, I've *NEVER* been bitten by a black widow spider!"

Correlation does not imply causation.

DS

It is a 1973 Ford Industrial engine, built on the "cusp", and I don't know if it has the hardened seats or not. The service manual specifies leaded fuel, though. My point was, the CD-2 Lead Substitute treats 200 gallons for about $12.00, and after 31 summers(actually, leaded fuel became unavailable after about 1982 around here) (200-300 gallons per year), the investment was low. It has never been apart, I hope it never comes to that, but it still runs wide open at 220+ HP & 4700-4800 RPM for extended periods and has never complained for a lack of performance. We've been using Mobil 1 oil since

1998 too. With the price of a 5 qt. jug only $18.88 at WalMart and only one oil change per year, why go cheap...

I know how "double blind" test are supposed to be run, but the OP only asked "Anyone else using a CD-2 Lead Substitute or any similar product?"

Also, as you know, eating carrots causes automobile accidents... over 90% of people in the US involved in crashes had consumed carrots in the prior 15 days...

Rob

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Thanks for the enlightening reply. I'm using the lead substitute in a

1964 Chevy Impala w/ V-8 283 cubic inch motor and in a 1981 Honda CB750 DOHC. Not sure if either have hardened seats. The Impala engine was rebuilt three years ago and has 120,000 miles on her. The Honda has 35,500 miles.

Not that it's part of the discussion or matters, but I somewhat miss the smell of regular leaded fuel exhaust. Reminds me of summers waterskiing, probably getting poisoned by the exhaust of the ski boat. ;)

Its funny to go to an airshow where WW-2 warbirds are flying, stand downwind on the ramp, and watch everyone turn their noses up and breathe deeply whenever a big radial cranks up and belches out a puff of sweet-smelling leaded avgas smoke.

YA but alas avgas must go away in a few years, as well. 2008 I heard.

mike hunt

Steve wrote: