Hello all,

Well, I met my neighbor tonight, turns out he's a mechanic. Don't know if that speaks well of him or not. We'll find out. At least he was able to guess what kind of engine my car had, although he does have a '71 Mustang in his garage right next to my Valiant. So one point for and one point against. Anywho...he said that I should be using a lead additive or that my "valves are gonna' burn out real quick." I've heard this before, and I've used it a few times in my '73 VW. Now the mechanic for that car said to simply use the premium every so often and not worry about it. So which is it, Additive, or stick to the expensive stuff?

Now I did do search for "lead additive" here and and i got 3 results. So any other searches I can do to lead to more info.

I eagerly await your insightful responses.

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The old white brick

Guess what? Your neighbor's full of $#!+

D/W

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If it ain't broke, fix it!

Don't listen to that joker anymore...


Run your slant on the cheapest gas you can find and forget about any additives.

Maybe his crappy ferd heads need the lead but your slant should be fine...

The lead additive is for cars that don't have hardened valve seats. The seats sink in to the head.

If you are really worried about it you can take off the rocker arm shaft and take a strait edge and put it across all the valves. See if some are higher than others.

The past few early 70's heads I've seen were fine.

Dennis' answer is correct and short.

Here's the long version:

Your daily-driver slant-6 will live a long and happy life on unleaded fuel of sufficient octane to prevent pinging.

The mechanism by which Lead prevented valve seat recession is commonly misunderstood. It's nothing to do with lubricating anything.

With an unhardened 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. The Slant-6 has ample exhaust valve seat cooling and stout valve material, and the valve itself is small enough relative to the combustion chamber area that you really have to abuse the engine before things heat up to the danger point.

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. The majority of the Lead 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 many of those engines that suffered under this low-octane unleaded really did need the lead (high load and/or high-RPM engines), the bulk 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 wide availability of high-octane unleaded fuels, which obviate the insufficient-octane cause of valve heating and subsequent localised 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 US-based 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 bottled 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 toxic, is known to crud-up combustion chambers, and is of highly 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, and many motorists used it on a regular basis with no ill result.

Smile and nod at your neighbour. When he's not around, take pity on him, for he drives a Ford.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Wow, my neighbor really is full of $#!+. Smile and nod. Sounds appropriate to me. Thank you all. And thank you SSD for the wonderfully informative post. Never knew exactly what was happening in those burnt out heads, now I do. Seeing as my car is a daily driver, and rarely if ever goes over 50 (for now) I'm not too worried.

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The old white brick

There are a lot of things that we all think we know that just aren't so, so cut your neighbor some slack. It might be useful to have a mechanic friend nearby ... they tend to have access to really useful tools!

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Yeah, but a lot of these crackpots think that just because they got a job changing oil down at Pep Boys, they are some kinda know-it-all and authority on cars. Usually, it was the only place that would hire a high-school dropout that couldn't read. There are still a few real mechanics out there, but they are very few and far between. ...and don't give me that "ASE certified" crap either, that is just a joke.

D/W

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If it ain't broke, fix it!

Didn't read all of Dans post but in a nutshell. Unless you continually hammer on it, do heavy towing and the like, etc. etc. you'll be fine with keeping the greenbacks in the pocket, [ok, maybe for gas!] than buying that stuff.

...and don't give me that "ASE certified" crap either, that is just a joke.

D/W[/quote]


amen

After I fried a valve using Amoco unleaded nearly 20 years ago, I started using CD2 lead substitute in my leaded fuel cars and never fried another valve since.

The redish deposit on the plugs doesn't seem to be a problem and I change the plugs at normal intervals. The substitute's cost is around $8/16oz, I use the recommended ratio 1oz/10gal,
so the operating cost is about $.05/gal.gas.

I view it as cheap insurance.

I also use the CD2 additive, only when I do a lot of long haul freeway driving. I view the stuff more as engine "top oil" but am not sure if it does any good.

The stuff is a concentrate so you get a lot of treatments per bottle.
Interesting that the manufacturer changed the labeling on the product a couple of years ago, now it says "For Off Road Use Only" but they sell it right off the shelf at all the chain Auto Parts stores...

I was more upset over the change in the bottle design, it use to have a real long neck that worked great with the "side fill" A-Body cars. The new bottle needs to be used with a funnel or you leak the stuff down the side of the quarter panel.
DD

I have a carton of those leaded stuff and I pop one in the tank only when I'm gonna really abuse my car. (I mean, lotsa wot, prolonged hi-speed drives, etc) so to say, when I drive alone and the wife ain't there otherwise, I keep it under 75 and everythign's fine. I got hardened seats last time I had a headjob done. I use the lead stuff just to boost up the gas. I also thing that your neighbour is full of $#!+. Tell him that you doubled or trippled te recommended amount of additive and see how he goes with the BS all over the other side on colateral effects. That'd be funny

By the way, lovely car. Looks pretty much like mine... what model is it? (I have earned the fool of the year award with this q.... don't slap me too bad, I'm from the third world.)

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Well, since I posted about my neighbor, I haven't heard a peep from him about anything. That might be because I haven't seen him since, but you never know. Seeing as I don't do all that much WOT or hard driving on the car I'm not too terribly worried about the lead additive.

Oh, and she's a 1971 Plymouth Valiant, if there's a seperate model number, I have no idea what it is.

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The old white brick

I'd say it's about 20 years too late on that lead additive. We took a look at the motor on Saturday morning. After installing the mopar factory electronic ignition, the motor was still missing and jumping all around under the hood.

Motor mounts look O.K., but they're sure working overtime. The idle was also set way higher than it should have been just to keep it running.

On a hunch, we pulled off the leaky valve cover and I noticed that it was mysteriously quiet valve tappets for a slant six.

Well, I've never encountered this kind of mass valve recession. All 6 exhaust valves had near 0 clearance. It took about a half a turn each on the adjusters before I could get the .020" feeler in. Intake valves were near perfect, so I don't think it was a case of a misinformed mechanic trying to quiet it down, but you never know.

Well, the idle smoothed out and I was able to set the idle speed way down. Readjusted the carb (a holley 1920) from 4.25 turns on the idle screw back to 1.5 turns. From the look on his face during the test drive, I think there was a noticable improvement.

The best comment was "the bog is completely gone" I should think so.

P.S. Did you see where I put the 1/2 inch wrench?

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1980 Aspen 225 super six

Yeah, I really have to thank Paul for all the help he gave me this past Saturday. Good God does the car run so much better now. Yeah, that pesky bog is 99% gone. I still get it right after she starts up and hasn't had any time to warm up.

The Mopar EI was crazy easy to install, and once it was in, very easy to learn how to set the timing on. You never really know how easy it is until you try or are shown in this case.

Same goes for learning how to adjust the valves. Once he showed me, yeah, felt pretty stupid for not giving it a try myself.

Amazingly it climbs the hills of Pittsburgh with an ease she didn't have before.

So I'll say it again: Thanks Paul

PS. As for your 1/2" wrench, I thought you only had the 1/4" and the 3/8" out. If not, it was last seen in the vicinity of your Aspen's left rear tire.

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The old white brick