Lead additive in low-mile, original SBC engine from 1966

[sodly]

Sorry if this has been discussed before (I know it has been).  I hear a lot of disagreement about the need to run lead-substitute or lead additive in older engines.  Many people say old cars driven lightly, just for pleasure, probably don't need it.  Others say a bit of Marvel Mystery oil in each tank is a good idea.  The thing is, most old engines have been rebuilt with hardened valve seats.  What about the ones that haven't?   

 

Here's my scenario.  I have a 1966 Chevy 327 in a low-mile, original pickup.  The mileage appears to be 34,000.  Not documented, but everything about the vehicle leads me to believe it's accurate.  This engine still wears it's factory paint and decals so I'm assuming that it has never been apart.  Therefore the heads are original and do not have hardened valve seats.  The pickup is driven sparingly, just a few hundred miles per year, if that. 

 

With an original, un-modified small block chevy engine like mine (with original heads) should I be worried about running lead additive/substitute?  

[Matt Harwood]

Lead was an octane booster. Period. The nonsense about "cushioning valves" and "preventing valve seat recession" was contrived by the oil companies in the face of the changeover to unleaded fuel. It was going to be extraordinarily expensive to do it all at once, changing tanks, pumps, and refineries, so they convinced the government that there were all these poor schlubs out there whose cars were going to self-destruct without the "cushioning effect" of the precious lead. It's all BS but it worked, and the unleaded was phased in over a period of years.

 

Gas was unleaded until compression ratios started going up in the '50s. Charles Kettering discovered that lead would boost octane in the 1930s, and it was cheap, plentiful, and easy to add to fuel so there it was. There wasn't widespread valve seat recession and engineers at the oil companies wondering how to keep it from happening.

 

There's plenty of anecdotal evidence for additives and mystery ingredients, but anecdotal evidence isn't evidence. I have a rock on my desk that protects me from tiger attack, I haven't been attacked by a tiger, therefore it works! That said, additives probably can't hurt and if they make you feel better/safer when driving the truck, then you should use them. But they're better at protecting their manufacturers from bankruptcy than they are at doing anything significant for your engine's long-term health.

 

Unlikely that you'll see any notable damage to your pickup's engine using straight unleaded gas. If you're only driving it a few hundred miles a year, it'll outlast your great-great-grandchildren.

[Bloo]

This was a hot topic in the late 80s and early 90s. It was thought that since the automakers were induction hardening valve seats in the unleaded era that it must be necessary. However, it turned out later on that the fears were overblown. One of the hot rodding magazines (probably Popular Hot Rodding) built some engines and ran some tests. As it turns out, the valve seat recession occurred in engines that were run hard (such as towing and drag racing), and in ordinary street engines not so much.

 

Hard seats are added to earlier heads by machining out the old seats and installing an insert. It is a rather critical machining process, and if you get it wrong, a seat can fall out and hold a valve open. That would most likely cause catastrophic engine failure. It happened quite a bit back in those days.

 

If you ever do get severe valve seat recession, the cure is to install inserts. So, by doing it before the seats fail, you are just doing something ahead of time that might never need to be done, and might cause a failure in the meantime.

 

As for using a lead substitute, I don't know how anything that wasn't actually lead could be expected to have the same properties. Also if it did help protect the valves, how would you know?

 

Yeah, anything can fail, but there is no way I would take that engine apart because of the valve seats.

[Frank DuVal]

55 minutes ago, Matt Harwood said:

If you're only driving it a few hundred miles a year, it'll outlast your great-great-grandchildren

 

This is right. Don't worry about it! Drive with unleaded and be happy. Use non-ethanol if it is available.

 

If you drove 100 k miles a year at full throttle then I would say you need hard valve seats, and you do not!

[padgett]

Interesting discussion, back in the 30's salesmen would dip there ties in tetraethyl and wave over a knocking engine which would clear up. They did not live very long.

 

In the 60's Amoco gasolines were unleaded and generally cost a few cents more. They recommended to run a tank of leaded every seventh fillup.

 

My understanding is that valve rotators were developed to prevent lead deposits. Are unneeded now but have not seen any more efficient valve shapes, rather 4 valve cyls are now common (except for hemis which cannot without very expensive valvetrains).

[Rusty_OToole]

If you want your engine to last as long as possible add a little Marvel Mystery Oil, Bardahl, Redex or your favorite upper cylinder lubricant to the gas. It will double the life of rings and valves. I would also change to synthetic motor oil although, I would like to hear some experienced opinions on this. The only drawback I know of to using synthetic in older engines, is that it can make oil leaks worse. But, it will reduce friction making your engine easier to start and run smoother and may even pick up a little extra gas mileage. And of course, reduce wear to a minimum.

[Pfeil]

12 hours ago, Bloo said:

This was a hot topic in the late 80s and early 90s. It was thought that since the automakers were induction hardening valve seats in the unleaded era that it must be necessary. However, it turned out later on that the fears were overblown. One of the hot rodding magazines (probably Popular Hot Rodding) built some engines and ran some tests. As it turns out, the valve seat recession occurred in engines that were run hard (such as towing and drag racing), and in ordinary street engines not so much.

 

Hard seats are added to earlier heads by machining out the old seats and installing an insert. It is a rather critical machining process, and if you get it wrong, a seat can fall out and hold a valve open. That would most likely cause catastrophic engine failure. It happened quite a bit back in those days.

 

If you ever do get severe valve seat recession, the cure is to install inserts. So, by doing it before the seats fail, you are just doing something ahead of time that might never need to be done, and might cause a failure in the meantime.

 

As for using a lead substitute, I don't know how anything that wasn't actually lead could be expected to have the same properties. Also if it did help protect the valves, how would you know?

 

Yeah, anything can fail, but there is no way I would take that engine apart because of the valve seats.

 

 

  Just a little correction here. Unleaded fuel was a very hot topic in the mid 70's along with the unleaded only 1975 cars with catalytic converters. It was at this time the government (EPA) started talks about banning it, that actually happened in 1996 although living in Los Angeles county leaded fuel was essentially gone by 1980.

 Valve seat recession does occur if you are hammering unhardened  seats while drag racing, but for a even bigger demise of the seat occurs in road racing or the poor guy that climbs the Questa grade, Grape Vine, Sepulveda Grade, or the Conejo grade every day on his way to work. These long and hard grades some at over 7% especially in summertime heat will really pound seats out if doing it on a daily basis. Low HP cars are doing these grades in low gears barely making 40MPH.

 

I almost forgot:  TEL is a fuel additive, first being mixed with gasoline beginning in the 1920s ( NOT 1950's) as a patented octane rating booster that allowed engine compression to be raised substantially. This in turn caused increased vehicle performance and fuel economy. TEL had been identified chemically in the mid-19th century, but its antiknock effectiveness was discovered in 1921 by the General Motors research laboratory, which had spent several years attempting to find an additive that was both highly effective and inexpensive.  

[padgett]

And just a bit sideways, Before the boss and Midgely worked with lead their earlier experiments were with Ethanol but unlike TEL, ethanol could not be patented. The rest is history.

[padgett]

and hardened valve seats became common after 72. Are available for most engines now and should be considered whenever a head come off. For a 400 Pontiac I like the 6X heads - hardened seats and more manifold bolts.

[sodly]

It's confusing.  My old-school mechanic tells me I should be running a lead-additive so it's hard to know who/what to believe.  Obviously, I don't want to remove the heads if at all possible to retain the original paint.  Puts me in a bit of a pickle!

Edited July 9, 2019 by sodly (see edit history)

[Matt Harwood]

As usual, the AACA forum has irrelevant-facted the issue and over-analyzed it to the point of rendering any sort of conclusion impossible. Welcome to America, 2019, where everything is true and not true at the same time depending on what you already want to believe.

 

Use additives if you want, it won't hurt the engine. You don't need it, but if you trust your mechanic then there's no harm. It's your money. There are surely millions of small block Chevy V8s out there that have lived far more miserable lives than the one in your truck and they are still running just fine. Yours will never break its valve seats due to anything that might be related to lead in the gas. Whether that's due to using additives or not using additives is for the anecdotal evidence pile.

 

 

Edited July 9, 2019 by Matt Harwood (see edit history)

[padgett]

I use an additive (CD-32) in my Judge with #12 heads. Not sure if still available but have a few years supply. As Matt said it may not be necessary but doesn't hurt. OTOH many years ago racers agreed that STP might save the engine if starved for a few seconds under high load.

Edited July 9, 2019 by padgett (see edit history)

[PFitz]

1 hour ago, Pfeil said:

 

 

  Just a little correction here. Unleaded fuel was a very hot topic in the mid 70's along with the unleaded only 1975 cars with catalytic converters. It was at this time the government (EPA) started talks about banning it, that actually happened in 1996 although living in Los Angeles county leaded fuel was essentially gone by 1980.

 Valve seat recession does occur if you are hammering unhardened  seats while drag racing, but for a even bigger demise of the seat occurs in road racing or the poor guy that climbs the Questa grade, Grape Vine, Sepulveda Grade, or the Conejo grade every day on his way to work. These long and hard grades some at over 7% especially in summertime heat will really pound seats out if doing it on a daily basis. Low HP cars are doing these grades in low gears barely making 40MPH.

 

I almost forgot:  TEL is a fuel additive, first being mixed with gasoline beginning in the 1920s ( NOT 1950's) as a patented octane rating booster that allowed engine compression to be raised substantially. This in turn caused increased vehicle performance and fuel economy. TEL had been identified chemically in the mid-19th century, but its antiknock effectiveness was discovered in 1921 by the General Motors research laboratory, which had spent several years attempting to find an additive that was both highly effective and inexpensive.  

 

 

That hot topic debate was even earlier in the 70's.

 

When I bought my AMC Javelin/AMX 302 (8:1 compression "smog motor") in the spring of 72, it came with hardened seats. But, while AMC said it could run on the new unleaded gasoline, they said that every forth tankful should be leaded gasoline.  

 

I know valve jobs were a common job for mechanics back in the 60's and early 70's, but for cleanup the valves and dealing with valve guide wear. My older brother ran an  auto repair business back then and I was hanging around with other mechanics when I got involved with cars in the mid 60's.  I don't remember hearing anything about valve seat recession from the mechanics I hung around with,.... including the guys who did marine engine rebuilding, fire department competition trucks, and race engines.

 

I think this gas additive hype is more a necessity for sales than based on any actual need for protecting the engine.   

 

Paul

[PFitz]

16 minutes ago, sodly said:

It's confusing.  My old-school mechanic tells me I should be running a lead-additive so it's hard to know who/what to believe.  Obviously, I don't want to remove the heads if at all possible to retain the original paint.  Puts me in a bit of a pickle!

 

Check the compression. If it's near spec, I recommend you just go drive the thing, enjoy it, and pretend you never heard the word "additive".

Edited July 9, 2019 by PFitz (see edit history)

[mike6024]

I wouldn't call Marvel Mystery oil a "lead additive." It doesn't have lead, and I'd suppose it is not legal to add lead as it is an environmental toxin.

 

Marvel Mystery oil has this:

 

Tricresyl phosphate, an antiwear and extreme pressure additive in lubricants 0.1-1.0%[2]

 

Rest of it -

 

According to the company's 2015 safety data sheet Marvel Mystery Oil is composed of:[2]

Petroleum Distillates (Hydrotreated Heavy Naphthenic) also known as mineral oil, 60-100%[2]
Petroleum Distillates (Stoddard Solvent) also known as white spirit, 10-30%[2]
Tricresyl phosphate, an antiwear and extreme pressure additive in lubricants 0.1-1.0%[2]
Ortho Dichlorobenzene, a softening and removing agent for carbon-based contamination on metal surfaces, 0.1-1.0%[2]
Para Dichlorobenzene, a precursor used in the production of chemically and thermally resistant polymers, <0.1%[2]

[sodly]

Ha ha!  Thanks, PFitz.  Perhaps there is no consensus on this topic.  Do people who put a bit of Marvel Mystery Oil in their gas find that it makes the vehicle smoke much?  Or any?  Or is it not really noticeable?  How much MMO do you use?  Sounds like MMO might be a cheap, simple compromise... if I decide to go that route.  

[Guest]

I don't see any pickle.  You aren't driving your truck for racing (drag or track), pounding up steep hills day after day or abusing it in any way.  Drive it as it is, put regular gas in it and stop worrying.  Change the oil and filter regularly, take it out on the highway a few times a year and blow the carbon out and when required in 75 or 100 thousand miles when you have to open the engine check for valve seat recession and report back.  OTH if snake oil makes you happy use it. 

The main thing is:  Drive your truck and enjoy it.

I have driven my Pontiac daily for 59 years, putting 400,000+  miles on a 99,000 mile vehicle.  Two engine overhauls, no valve grinds in between and no seat recession.  Just finished my third overhaul, this time I had to replace the guides for the first time and fix 15 cracks in the block.   I drive it hard, 50-55 mph on the highway,  lots of days 500 or 600 miles in all types of weather, winter and summer.  

[padgett]

Which brings up an interesting topic: yes most mass production engines under about 10:1 compression and 4" bore (see "flame propagation rates") are reasonably safe under light duty on 93 PON. It is the "interesting" engines that may need more protection but few of these are driven often and mostly use race/AV gas. My 10.25:1 400 is kinda marginal so I add something mainly for my peace of mind.

 

Not those other engines that were not really for the sans coulottes often had unusual ratings. Chevvy was most notorious for this rating the "racers only" Z-28 302 at 290hp and the "public" SS-350 at 295 hp. Also the single quad L88 at 430 hp and the pundits top tripower at 435. Right.

 

Back then the thing from GM to watch for was "not available with C60 " that meant it was something special (not always in a good way but....) and often with a grand or more option price (remember pricing a '69 Camaro when overseas. Three grand for the car and three grand for the engine. Never saw that before but was RPO ZL1.

 

[Bloo]

You guys are right of course about the lead debate dating much farther back. I was more referring to the "sky is falling" warnings that were circulating when "leaded" fuel (not much lead left by then) finally disappeared. Everyone was gonna need hardened seats installed in their heads, or need to use smog-era heads with the induction hardened seats, etc.

 

There was some discussion in those days about guides, but it wasn't the main thing. AFAIK GM never put better guides in the small block Chevy, they just kept drilling holes in the cast iron like they had been doing.

[Pfeil]

42 minutes ago, sodly said:

It's confusing.  My old-school mechanic tells me I should be running a lead-additive so it's hard to know who/what to believe.  Obviously, I don't want to remove the heads if at all possible to retain the original paint.  Puts me in a bit of a pickle!

 

 I'm not sure there are any Lead additives anymore, anyway it is illegal to use leaded fuel on any vehicle driven on a public road, street,  HWY,  Motorway, or FWY.

[Pfeil]

31 minutes ago, PFitz said:

 

 

That hot topic debate was even earlier in the 70's.

 

 

 

Paul 

 

Paul the reason I said the middle 70's was because we all got concerned that the gov. was going to eliminate lead completely. Before that is was all the hype about new cars being unleaded only. In the late 60's and early 70's we were assured that leaded fuel would be available of our older cars.

[Bloo]

49 minutes ago, sodly said:

It's confusing.  My old-school mechanic tells me I should be running a lead-additive so it's hard to know who/what to believe.  Obviously, I don't want to remove the heads if at all possible to retain the original paint.  Puts me in a bit of a pickle!

 

If in doubt, don't take it apart.

[PFitz]

37 minutes ago, sodly said:

Ha ha!  Thanks, PFitz.  Perhaps there is no consensus on this topic.  Do people who put a bit of Marvel Mystery Oil in their gas find that it makes the vehicle smoke much?  Or any?  Or is it not really noticeable?  How much MMO do you use?  Sounds like MMO might be a cheap, simple compromise... if I decide to go that route.  

 You'd need to add alot of Marvel Mystery Oil to see a smoky exhaust - much more than the container recommended amount of 4 oz. for every 10 gallons of gasoline. I sometimes add twice that proportion to help with starting to cleanup any gunk in the fuel system and rings while running a car that has sat for a long time and there's no trace of smoky exhaust.

 

MMO is no mystery. You can look up the MSDS sheet for what it's made of. It's more cleaner than oil. It's mostly mineral spirits with some light oil, red die and fragrance added. And the mineral spirits burns rather cleanly.  Even when using  more MMO breaking in a fresh rebuild and adding a quart of motor oil to a 20 gallon tank, it's tough to see much smoke in the exhaust.  

 

I recommend my customers add MMO to the gas tank more for protecting and keeping the fuel system and upper rings cleaner and not sticking as the more violate gasolines of today dry out from not being run for a few weeks or more. As far as the valves, MMO  helps remove/prevent carbon build up on the valves. 

 

Paul

Edited July 9, 2019 by PFitz (see edit history)

[JACK M]

Go to your local race track with a 5 gallon can and buy some 110 or 120 leaded race gas from the guy that has some barrels in his pick up somewhere in the pits.. $10 - $15 per gallon.

Put a gallon or so once in awhile.

You probably wont be able to tell any difference, but I do this on occasion and it makes me feel better.

DO NOT use it in vehicles equipped with catalytic converters.

[Pfeil]

22 minutes ago, JACK M said:

Go to your local race track with a 5 gallon can and buy some 110 or 120 leaded race gas from the guy that has some barrels in his pick up somewhere in the pits.. $10 - $15 per gallon.

Put a gallon or so once in awhile.

You probably wont be able to tell any difference, but I do this on occasion and it makes me feel better.

DO NOT use it in vehicles equipped with catalytic converters.

It's illegal to use on a public road for the second time! Don't encourage someone to do something illegal.

[Matt Harwood]

Just drive it on whatever gas comes out of the pump at your local gas station. Anyone want to suggest that's a bad idea?

 

Let's end this nonsense before the cloudy waters become opaque, eh?

[60FlatTop]

I have been driving a 10.25 compression ratio 401 Buick for the last 15 years on regular pump gas. It had 69,000 when I got it, about 88,000 now. I use it in everything but a modern car that strictly specifies premium.

 

I use Mobil which is considered a "Top Tier" gasoline: https://www.consumerreports.org/car-maintenance/study-shows-top-tier-gasoline-worth-extra-price/

 

Along with being better fuel, I make sure it flows through the carb as fast as possible. Sitting around is no good for old cars or the fuel in them.

 

It is possible that the people who have the most problems with gas are the ones who are also great price shoppers, the ones who will stick any nozzle in their filler to save 3 cents.

 

Back in 2016 I started having poor idle symptoms and stalling at stops. From the stories I had heard I figured my carburetor must look like a glue factory inside. 8 years after I had rebuilt the carb I removed the cover and found this:

 

Pretty clean after all those horror stories. The problem turned out to be one of those new condensers. Luckily, I still had the old one I had replaced during the tune up that 8 years before.

 

Didn't even have cloudy gasoline in the carb.

[PFitz]

1 hour ago, Matt Harwood said:

Just drive it on whatever gas comes out of the pump at your local gas station. Anyone want to suggest that's a bad idea?

 

Let's end this nonsense before the cloudy waters become opaque, eh?

  It'll never die, Matt. 

Just like the topic of using non-detergent oil. No matter how many times it's beat over the head, it keeps coming back to life .

 

Paul

[sodly]

Sorry for beating a dead horse, guys.  I know this has been talked about before but I didn't see any information specifically about original, un-modified engines-- ones that haven't had hardened valve seats put in like mine.  

[Ray Bell]

I do know how to get myself in trouble...

 

The following is my experience with valve seat recession.

 

I first experienced this in the Toyota 12R engine (I think that's the right designation, 1600cc pushrod) in a Hi-Ace. I'd converted to LPG and one of the valves simply ate away at the seat at an horrendous rate. It was buried in the hole over 4mm down (I kept adjusting the lash) by the time I changed the head. Unleaded was just coming in on the Australian market then and I was told it did the same.

 

Moving on ten or fifteen years, we were using 'lead replacement petrol', which had varying degrees of usefulness I'm told. Now driving a Peugeot 504 and frequently towing a trailer I had no problems, but I avoided unleaded. Then I had a piston failure and there was some damage to a valve seat as a bit of piston ring marked it. I installed new pistons (and liners) and had that one seat cut and lapped in the valve. All the other valves and seats were untouched.

 

In very short order this one seat dramatically ate itself away. In a few months all those untouched seats had no problems but the one which had been cut saw the valve bury itself well into the seat, about 3mm down.

 

Understanding that the various brands of what I call 'tin canisters, which are marketed under many names, worked to save valve seats by leaching tin into the fuel, I ordered one. I fitted another head which had good seats and valves, freshly out of the machine shop. But I had to drive 1500kms with a trailer before the tin canister would arrive.

 

Each exhaust valve required adjusting after that time, about 0.015" on every single one of them. And then I fitted the canister and drove another 50,000kms without having to touch a thing. The 'lead replacement petrol' wasn't doing any good at all.

 

I found at the time there is a simple fact relating to these devices. Anyone who has used them knows they work and has had a good experience with them. Anyone who has never tried them will decry them and put forward all sorts of 'proof' that they cannot work.

 

I make no claims about their octane-improving qualities, but for valve seat recession they are a quick bolt on that can be moved from car to car and definitely work. Further proof came when I had my next experience. Suddenly the valve seats started to wear away again. I contacted the maker and he asked what fuel I was using. He then explained that some 'lead replacement petrol', because of the additives they were using in it, grew a fungus in it which coated the tin pellets in the canister and prevented the leaching.

 

I had to dismantle it, clean them with bleach and then reassemble it. Simple. And it was back to working again, just like that.

 

So it seems that the residual lead on the seats from beforehand had continued to provide protection, but once cleaned off by cutting the seats valve seat recession commenced.

 

So either don't worry about it or fit a tin canister just to be sure...

 

And for those about to post that I don't know what I'm talking about, that it is 'snake oil', save  your breath. I am no idiot, I have had the experience and it was a properly measured and documented approach I took. Nothing else intervened and nobody else touched my engine.

[padgett]

Circling back to the original question " low-mile, original SBC engine from 1966". To answer I'd need to know which SBC is being discussed. '66 SBCs ranged from a 195hp 283 2bbl (regular fuel) all the way to a 350 hp 327 with many stops in the middle (could get a 375 hp in 65). What fuel or additives we are talking about depends on which SBC (the 275hp 327 was a really nice Impala combo but required premium fuel). L79 & Muncie in a SS Nova was even better.

[sodly]

padgett, this is a stock "hi-torque" 327 truck engine.  Pretty sure it didn't require any special fuel back then.  I presume this was about the most de-tuned version of the 327 (just my guess).  Definitely not a Corvette motor.  The says there were two 327 versions for trucks, one (185 hp) at 8.0:1 compression and another (225 hp) at 8.5:1 compression.  I believe mine is the 225 hp version from what I'm seeing in the literature.  Looks like the 185 hp version was used in larger straight trucks. 

 

The "Turbo-Fire" 327, by comparison, had a 10.5:1 compression ratio.   

 

Regarding the valves, the 1966 truck sales book says this: 

 

"Induction hardened exhaust valve seats.  Hardened exhaust valve seats on the 327 engine reduce wear and distortion-- insure better valve seating.

 

"High alloy steel inlet valves.  Tough high alloy gives extra durability.  Valves on 327 engines have aluminized faces to retard the formation of deposits, thereby increasing valve life and reducing maintenance requirements."  

 

"Long life exhaust valves.  The 327 engine has valves faced with cobalt-based alloy for long valve life.  Aluminized head retards build up of deposits and chrome plated stem reduces scuffing and wear.  Aluminized valve faces on the 283 engine with applications in the 50 series trucks slow the formation of deposits, keep valves cleaner and longer-lived."

 

"Hydraulic valve lifters, both inlet and exhaust."  

[Frank DuVal]

Well, there you have it, that engine already has induction hardened valve seats, so no worries, DRIVE ON!

 

Do not worry yourself into an early grave.

[Marty Roth]

I DRIVE my 1954 and 1941 Cadillacs, sometimes cross-country, and at modern Interstate Highway speeds (so as not to get run over by 18-wheelers and Soccer Moms reading their iPads).

 

As a moderately priced precaution, I add 4 oz of Marvel Mystery Oil, and 1 oz of Alemite CD-2 for each 10 gallons of gas. If the gas has Ethanol, I also add appropriate portions of Star-Tron. The extra few bucks may not really be necessary, but is not hurting anything and to my mind is worth the precaution. I do the same for the '65 Corvair, '37 Buick Roadmaster, and '88 Corvette. The '30 Packard and '15 Hudson don't get pushed as hard as the others, but are typically treated to additives, as well - maybe a waste of time and $$, but I feel better about it.