Is Modern Gasoline Killing Your Classic Car's Engine? 

Tony, you missed one of the biggest advantage of unleaded fuel, reduced cylinder wear. I'm an aircraft mechanic and still deal with lead in the fuel. It's a long read and if you are a engine nerd, read the Army Corp of engineers study on fuel in WWII, it was found that adding lead was an easy way to reduce detonation in the large aircraft engines. They found that adding Ethyl Bromide would help scavenge the lead out of the cylinders with enough heat. They also found that Tetraethyl Lead accelerated the wear on the cylinders and rings. The benefits offset the wear on these engines due to the fact they were designed with a 4-500 hr service life. I often have heated debates in the aviation community over this, the engine in my airplane which is a Continental O300 has a 7 to 1 compression ratio and was designed for 80 octane unleaded not the 100LL at most airports. This often leads to the valve stems gumming up and alot of wear in the cylinders because the temperature of the combustion is not high enough on a low compression engine to allow the Ethyl Bromide to scavenge the lead out of the cylinder. I have been running non ethanol 93 octane mogas in my plane for the last decade, I have not had to replace a cylinder and my compression is perfect. Now aircraft engines have an aluminum head with steel valve seats so valve wear is not a problem compared to soft cast iron used on old car engines. Which brings me back to cylinder wear. The rings in an engine when I was a kid would be toast at about 70,000 miles, then unleaded fuel came out and now a Honda is just getting broken in a 100,000 miles. The cast iron in the block hasn't changed, if anything it's softer with less nickel in it and you could say the rings are thinner with less tension but either way the bore isn't as choked out as it was with leaded fuel. Most modern engines run aluminum heads with steel valve seat these days so the valve wear is long gone too. I don't care for the subsidized ethenol being put into the fuel, at 10 percent there really is no value and only harm. Once you get to E85 then you can make some serious power. Another downside to 10 percent is about 10 percent less fuel mileage as alcohol need to run at almost twice the amount of fuel to air as gasoline. But I would never want to go back to leaded fuel, that was a cheap easy way to make crap gas available during wartime good enough to not melt the pistons of high performance engines found in the late war aircraft

On the small engines like in lawn mowers. Always close the petcock for the fuel system while it is running and run all of the gas out. It really helps a lot of things.

Professor Tony again :). Using a combination of science, politics, history, and infrastructure to explain a mechanical question. I still think you need to wear a tweed jacket with elbow patches when you have these kinds of videos. Love it!

Fun fact, the fuel additive tetraethyllead was distributed by the Ethyl Corporation of Richmond, Virginia. That’s how premium gasoline came to be called “Ethyl.” 😎

Everyone has a story about ethanol. Mine is that I unknowingly ran my old van on 10% gasohol for about a year. The gas station I used didn't post its pumps. Result? No engine damage as far as I could tell, but the damned alcohol "scoured" the bottom of the gas tank, allowing years of crud to be sucked into the gas tube which would then kill the engine. After a few minutes it would start again since the crud fell down when the suction stopped. Two trips to the shop, no one could figure out what the problem was. Then I accidentally discovered the ethanol in the gas, dropped the tank and had it professionally cleaned, and now the van runs like a top. That same gas destroyed the fuel line on my snowblower, filling the float bowl with bits of line. Great fun to have in the middle of winter in the not so great North. My take on ethanol: it's crap. Hard on fuel systems not specifically designed for it, takes virtually as much energy to make as we get out of it, and actually causes more pollution to make than does gasoline.

Uncle Tony you just explained why as a kid I used to have to replace push rods on my 6 cylinder AMC , It used to bend one every second week or so. I had it down to about 15 minutes to pull the old one out and replace with a straight one. I used to get straight ones from the junkyards and kept a supply in the glove box.

Project farm has a great vid on the effects of ethonol on carbs And other fuel parts. A really good watch.

Driving style has a lot to do with this as well. My Aunt Mae would burn the valves a lot, but it was because she idled everywhere she went (35mph was fast for her & it scarred us for life riding with her). My Uncle Glenn would have to take it out on the hwy about once a month and drive it like a drunken teenager to blow the carbon out of it. Because of that, dad had to do a lot of head work for her (and many other things) because she would just load that poor Nova solid with carbon (esp after Uncle Glenn passed away).

You should talk about zinc oil additives some time. I put some of that in my engine along with some good filters.

My race trapter was sitting for over 2yrs now, I figured it would be a good idea to get it out if mothballs. Always used stabilized fuel, and it was drained. Still has an odor in the tank and the rubber duel lines are hard as a rock. Might as well drop the carb bowl and see what's up there too. Ethanol sucks for storage, and making it from corn is a loser but the corn lobby is huge you're never gonna stop them.

Fuel pump diaphragms seem to have a shorter life than they did in the past. Ethanol gets all the blame for everything, but other components in the gasoline blend have had to change over the years, sometimes more than once in response to government regulations. Lastly, gasoline is a product that is likely blended for specific regions, seasons, even altitudes. If the location happens to be a populous place like Los Angeles, there can be different blends for areas within the city itself. You nailed it Tony, with your explanation of all the trouble that happens with small engines and gravity feed fuel tanks.

My first hand me down car in 1988 was the family 1974 Valiant (318). I remember the Sunoco by me still had “Regular Leaded” into 1989 I used to buy. Also, it was under $1.00 per gal. I remember when it hit a buck!

EFI fuel hose is what you use to solve the fuel hose problem it lasts alot longer

Good information for anyone getting into these older cars. I drive a 1968 Plymouth Satellite, and when I got the car the valve seats were actually sunk in so far and with so much guide wear that the shop I took it to didn't believe me that I'd been driving it for a few months. Had as you described, a very prominent miss that would get worse with higher RPMs. Drove ok in town, but couldn't do the highways. Had hardened seats installed, and the 318 has ran like a sewing machine since

Gald you mentioned a maybe for the old heads. When I sent my '65 383 to the machine shop I expected to have to have hardened seats put in. He told me nope "They are hardened" and asked me if I was sure they had never been done. I pulled it from my '65 Sport Fury I got from the original owner. Totally never touched.

You're spot on Tony once again in Australia we didn't put harden the seats in the heads that's why you especially notice it with LPG . Great work thanks .

I asked this question last week. Thanks for all the info Uncle T. Now I know how to check that my valves are good and great to know for future junkyard rescues!

Always use Seafoam when storing anything gasoline powered for longer than 2 months. Seafoam also takes away the corrosive effects of ethenol so fuel hoses won't dry out or accelerator pumps etc.

If you pull the plugs out of the top of an older Holley metering block you will likely find a white powdery substance at the top of the well tubes. Unknown if it's left there from additives after the fuel evaporates or caused by ethanol reacting with aluminum/steel in the fuel system. Explains why they get flaky with age. New metering blocks ($70) would probably fix them.

Brilliant - I’m remembering any number of Mini and Morris 1100 heads with badly sunken valves here in hot Western Australia back in the 70s and 80s, but never understood what had happened until today. Since I could swap those heads out in 30 minutes, I just hand reseated the valves on a spare head and swapped it in when the one in the car started to play up.

The C heads on my 68 Toronado looked beautiful under all the grime. No etching / scratching everything was nice and smooth. Compare that to my buddy's 54 Jeeps just eaten until the valves just fall in

My old car fuel systems have been very trouble free (knock wood) since ethanol, but I did replace the rubber parts with compatible parts, AND I drive them enough to replace all the fuel in the tank a few times a year, minimum. You are DEAD RIGHT! about small engines with gravity feed carbs. When you park them, the carb acts like a distillery… the fuel evaporates from the bowl, but the additives don’t. Gravity replaces the fuel and more additives come in, repeat, repeat, repeat, until you have a carb bowl full of sticky, gooey, crusty distilled additives that plug the jet which is usually at the bottom of the bowl. Putting a little fuel shutoff valve in the fuel line (and remembering to close it before storage) solves 99.99 percent of those problems.

Awesome video Tony, it should help a lot of people.

As a standard practice when I used iron heads, the valve seats were replaced with Stellite seats. All valve heights were checked both with and without springs, spring heights and stretch and tension and shims added if springs needed. These little things were often overlooked.

I ran unleaded gas in my '55 Buick for a long time with no issues. The next car, a '68 Impala, was run on it for the 10 years I owned it- '85 to '96-and had no issues. I now run my '37 Dodge on it and it runs fine. The only time I used a lead additive, which was on the Impala, it fouled out the spark plugs.

11:10 With the heads off the engine, I can see how using a straight edge would work without removing the rockers if installed. Tons of knowledge as always. I love this channel.

This is the best explanation of the lead in gas issue I've ever seen. One thing you didn't mention is how incredibly toxic tetra ethyl lead was. It was pretty dilute in gasoline, but get it full strength on your skin and you were in for a very bad time.

TY,Tony for sharing your knowledge!

Another very interesting video. I always get something out of these. Thanks for the knowledge.

ALL 1960-69 Chevy Corvairs had hardened valve seats installed in the Aluminum heads and are perfectly happy with Unleaded Gas. The problem they have is that over decades of heat cycles, some engines start dropping valve seats; this is most common in the "Big Valve" 140HP heads.

Catalytic converters were optional on forklifts since the early 50’s. They were never mandated for cars. But the emissions specs tightened to where “all cars” needed them. Some AMC cars and Subarus burned clean enough without them for a couple more years. The cats allowed the engines to revert to the more powerful specs of, say, 1972 so adding them actually increased performance.

cool video. So much info to take in about this issue. Thank you for telling us all about what it is all about.

Wonder if the chrysler 516 head castings had different metallurgy than other head manufacturers at the time. I have a chrysler 361 with 516 heads and have no sunk valves, it's being driven daily and the somewhat occasional WOT romp. Edit: High RPM situations may promote more valve seat etching, while at normal driving RPM 700/900 may not be enough to start eating the seats away. Just some food for thought.

I think alot of that depends on the application n set up. Are you pushing the enging hard? Runnung it lean? Is it a 318 in a boxtruck with glowing red manifilds or a 383 in a Dart running cool, rich with low gears?

That straight edge trick is great. Thanks tony

Good info According to Tony at Ross Racing, my 1964!Oldsmobile 394 had extremely durable seats and didn’t require hardened inserts.

I drive an old carb car from the 60's on 10% ethanol, no problems at all. I did replaced all the rubber lines with modern lines.

Great explanation & lesson once again Uncle Tony. Cheers 😊

We did a 68 302 for my dad's 53 F100 in late 80s. 3o years and about 30K miles later he complained it was running like crap. Turns out the exhaust valves were so far into the heads, they couldn't close anymore. never seen anything like it. I always thought seat recession was a myth till I saw that.

Legend so much info so simple to understand keep em rolling

The straight edge idea helped. I knew most of this and my theory was that the high heat on the valves from lack of lead would do like a case harden. lots of parts on heavy equipment have soft shafts with only a 1/4in. of hardened steel on the shaft. Now I can check my 1966 nailhead without tearing too much apart. It runs fine but I didn't put any additives in or premium gas just drove it.

Excellent video! Great explanation of a very real, but poorly understood gearhead/car guy problem.

Got alot out of this Uncle Tony!!! How about tutorial of one of the vintage sears engine analyzers? Different hookups ect. Thanks

Hi Uncle Tony. Fantastic video! I own a 65 Plymouth with a poly 318. How often should I put a lead additive in my gas? Is it necessary to use an additive every time I fill up my gas tank?

A friend of mine has ht holden with a blown 383 chev running e85 when the engine was new he made the mistake of storing the car for 3 months without flushing the fuel system with standard fuel..when we pulled it out for a car show we found that the valve guides were stuck to the shafts..it was a simple "tap it with a hammer fix" but lesson learned. He now drains the carb,tank and flushes with a lean 2 stroke mix prior to storage. E85 is terrible for drawing moisture as it evaporates. I have also heard of people using kerosene and atf to stabilize the fuel in the carb if it's going to sit for a while

Ethonal evaporates and draws in moisture, water.. You will get a layer of water in the bottom of the tank if it sits.. Doesn't take long either... My other main gripe is it messes up plastic and rubber pretty quick.. I never use it in my 2 strokes...

The lead left considerably more deposits behind in the crankcase, it wasn't unusual to find loads of gack under the valve covers blocking the drainback passages.

Perfect explanation of a by gone era.👍👍👍👍👍🌟🌟🌟🌟🌟 Another solution to keep the valves from eating the seats if you have all the proper tools is to widen the contact area on the seats and valves when you're resurfacing them, it's very very time consuming but it will work, just don't make it too wide or it could eventually burn and/or crack the valves, but when done correctly no problems, it also ensures a better seal during the power stroke.

On my Ford 2.3 lima engine, I had oversized valves installed during a performance rebuild, and a few years later had burnt seats and ruined valves from running lead free gas. Apparently the seat hardening was removed or compromised when cut for the bigger valves. I also had new lawn equipment failure due to ethanol fuel errorsion. That industry needs to upgrade like the car manufacturers have done to handle at least the 10% blend at most pumps. Now I make sure the fuel is very fresh and use a popular additive for storage.

Tarrel Fixes all does a year long fuel test with multiple engines using all kinds of fuel additives. All the fuel additives gummed up the carbs and non ethanol canned fuel and 87 octane only thing running after a year. Fuel additives dont do crap for ethanol. Actually makes it worse according to his test

It is fun because you always seem to come-around to addressing what really matters. In my engine building days the split was between performance and dependability. In the case of the work rigs vis-a-vis Mail trucks etc.carrying heavy daily loads in Urban traffic; every single head got hardened gas seats. If they were too far gone, we used a large press, drilled and inserted molybdenum press fit seats, w/ the theory that the new seats would be far harder(BHS) than valves. Additionally, in Physics during the stoichiometry section, very simply if your combustion chamber is at the sweet spot of 67-69 cc's and one finds X5 sunken valve seats, this increases space or fuel volume which as we know in a performance application decreases compression. +V=(-P)+(-T) Decrease in P of course equals a decrease in compression. In 1996-98 enter the fad of + deck height numbers to increase compression.

Fascinating Tony! I was told that my 1980 318 Chrysler had hardened valve seats. After watching this I believe it does?’

My Dad went To Hoover High School in Glendale California in the mid 60’s he said you can see the smog from the Vehicles in the hallways.

Lead substitute “Cliff Notes”: Take a straight edge across your valve springs. If they’re relatively level ok to use. If not, “The cow is out of the barn”. Don’t bother buying lead substitute in that case. I love it Uncle Tony!

Now I know how to decide if an older engine is going to be needing to have the valve seats replaced without having to take the heads off. I can’t wait for decent weather so I can check my 63 318 Poly to see if it is going to be needing it or not

dude i got like 10 things outa that, thanks UT! such good info

nice tut on this matter, better understanding on how fuel affects engine

Good stuff, UTG!

Tony's words are true. I have some supplemental info from my experience with English triples from 1969 to 1975 (BSA and Triumph). These engines run on the hot side, and valve face and valve seat wear was quite fast. I would recondition the heads with three angle valve jobs and new valves, guides, and springs. 4 thousand miles later (not sparing the whip miles), the seats and the valve faces were quite worn and damaged. Craters of the moon type damage. I tried the Lucas top cylinder lube additive in the gasoline. I was quite impressed to find the face of the valves were no longer cratered, but very smooth looking. I think it helps a lot!

Yo Uncle Tony! I'm curious about your thoughts on the Fitch Fuel Catalyst (in-line) and the application for a 99 Dodge Ram 1500. From what I've seen there's not a whole lot of information about the improvements but my thoughts are that it would slightly improve gas quality for cold starts and possibly improve mileage (small gain = big gain overtime) I really appreciate your videos these past couple of years!! Learned a ton more than I ever would from just trying to read. Take it easy dude! Thank you for any info or opinions in advance! See you tomorrow! 👊😎

Great explanation of sunken valve seats. Now if you have an engine from the 60s and it has more than a couple of thousand miles on it (maybe some car that grandpa bought and never drove) it's time to take it apart and rebuild it with some hardened (stellite) seats.

Nice show, Thank you

What would cause intake valve wear on a classic engine? I took the head off the 200ci in-line 6 on my 1966 Ford Mustang to replace the rings and the intake valves where in really bad shape. The intake valve guides where also shot. The exhaust valves on the other hand where in beautiful shape, no guide wear, the seats and valves where not sunken in or anything, they looked great. The intake valves where in worse shape than the seats, not very uniform, definitely overheating and not uniform enough to seal really well.

Great explanation!

God bless you old man. You are so helpful

Awesome videos Uncle Tony, I have a 68' Ford Ranchero with a 302 and I think that the transmission is a C 4, the trans has leaked out all of the fluid, I found a rebuild kit online. I've never actually even pulled a transmission but for some reason I believe that I can rebuild it. Can you do a video about transmissions? I wish that I could bring you the vehicle to do a video on the subject. I'm really enjoying your videos!

Check replacement carburator needle / seat , tips of needles made of a material that may react with ethanol also, the material that they use for the float itself , some floats are no longer brass , same for the floats in fuel tanks

Fine job Tony!

Modern gasoline will kill your cylinder heads IF they are PRE 1971! In 71 they started hardening exhaust valve seats. Prior to that they are NOT and that's why there was Leaded gasoline. Now I have personally seen exhaust seats beat up into the head about 1/8 to 1/4 inch, On 2 different sets of heads that were PRE 1971. You CAN have your older heads fixed and have hardened valve seats installed and that will fix the issue or just use a lead additive. Now the ethanol increase is a whole other discussion.. Edit: After I watched the video Tony covered this. Good job Tony!

Imo🤔 valve guide gaulding or poor lubrication in guide/valve area is the death of old cars now. Excellent job on trying to make sense outta that era and good job explaining these issues, basic on all engines 👍 Thanks for sharing

Hey Tony, great video, but thought I'd like to add a comment as a 35+ year experienced mechanic/engine builder. The lead content was also very important in the longevity of valve stem guides and sealing. Old cast iron heads can be fitted with stainless valves without the need for hardened valve seats to slow down the issue of valve height/recession problems. Mostly overlooked beyond valve seats, as with this video, is the importance of the use of lead for valve stem/ guide lubrication. There must be some type of lubricant within the intake fuel charge to lubricate the stems and guides. These will wear much quicker than valve seats and damage an old engine to the point of rattling and smoking due to worn valve stems and seals. Awesome channel mate, love ya work and sending all our best wishes from us petrol heads here in Australia 😎

They only thing I have is where I have to crank my car forever if I don't feed it gas. Only have to if the car sits for more than two days. Evaporates completely. Really annoying

Yes, my father and uncles as well as grandpap often talked of the time when there were NO SPEED LIMITS and little limits on bravery!

When leaded gas was phased out the automakers had to add extra sections to their head machining lines in order to induction harden the valve seats.

One of the coolest tricks my dad showed me was holding a sliver of paper at the exhaust tip. He showed me on my old 350 pontiac. A shitty seated valve would cause the paper to be Sucked into the exhaust at intervals.

That's the answer to all my troubles right there it was the lead always in the garage for cold starts prior to 1976 and chewed on the window sills in the sixties can't make sense of nothing since the 90s🤪⛽🇺🇸😁

Thank you UT!!👍

Hey Tony. Thanks for doing your part to keep hot rodding and common sense alive.

I liked that information I have a 71 F 100.with a 302 around 150.000 miles.

Some interesting information... I've been wondering about this actually since I've got a set of #188 square port BBC heads I've been thinking about using, but I know those didn't have hardened seats, or at least I don't think they did. They're not sunk at all, but I know it gets dicey putting hardened seats in a BBC head cuz you often hit water when machining for the seat, then the head is junk. These ones show no real seat wear at all, unlike my #781 oval ports that the old owner ran on propane, and all its exhaust valves are sunk probably 1/8" at least.

Great stuff. Lots of old wive's tales out there.

Ethanol gas is objectively bad in most ways economicly, efficiency wise, the gas, shelf life is worse, it has less energy, it doesn't help the environment, it can increase octane if more is added to gas. I would buy pure gas, but I don't want to go to specific stations and I don't want to pay more for gas.

Uncle Tony is such an awesome guy , I really appreciate how much of a gentleman he is , like a breath of fresh air indeed. However I also love the smell of a mixture of fuel and burning rubber as well , #MakeAmericaCarberatedAgain !!!

EPA didn't exist until '70. Lead was gradually phased out STARTING @1973. Clean Air Act wasn't passed until 1996. The government knew about the effects of lead as far back as 1923, but congress couldn't really act due to the overwhelming industrial push for no regulation.

Great explanation!! I'm new to carb cars, I have a 63' Ford and I'm not using a lead additive in my original (never rebuilt) 390FE. It's due for a rebuild anyway so why not just run straight unleaded. Thank you for this video! I wish there was a UTG for Fords!!

I have caught the bad end of this about 30 years back. Heads are long gone now [cracked], and as retired there was zero sign of a valve job left: some kind of bowl remained instead of seatwork, and recess was probably around 0.050" and most valve guides had gone egg shaped. Guides were iron, not bronze. Its last hurrah was a coast to coast road trip, the latter half of which had me so nervous I was afraid to shut it down - went Dallas to LA, hot pumping every stop. Built a new motor on arrival, keeping only the manifold and distributor. In honor of that miraculous trip [yes, I logged one 11 hour section of 24mpg], that dizzy will be going up on the wall - but it's still running for now, and it's... busy.

Probably been said in the comments but what I really want to know about is modern OILS and vintage engines. I hear you need to run diesel oil in 70s motors because of the cams. Hope Tony does a video on that.

Thank you!

Do you have anything, videos about zinc in oil for an older vehicle?

Here's an interesting topic you and I lived through!

I'm only running 91oct rec fuel, non alcohol in my 91coupe DeVille, They weren't pushing gas cut with alcohol when it was built, I ain't taking chance with it. It definitely caused problems with my Old 83honda.

When they started adding the ethanol the problem I had was it reacted with the metal of my carb (stock Autolite) which caused the fuel to foam up. Car would barely run. Arco was the worst of all the brands. Changing to a Holley greatly reduced the problem.

You mean the unleaded corn squeezin blends, good stuff.

I agree with some points brought forth here but I have experienced problems with methanol enrich gas actually causing the inside of carburator bowls to dissolve the interior surface of bowls leaving a thick residue in the bottom of bowls which eventually fines it way into the rest of the carb internals. If that's not enough head ache, on engines that sit more then run the methanol will separate from the gas which can lead to moisture and more corrosion in the carb. It gets even worse if you try to use methanol gas in small 2 cycle engines, the methanol will eat up the interior of the small engine carb guickly.

Apart from the destructive effects of ethanol on the fuel system is that ethanol doesn't produce the power of gasoline. It eventually reaches a point of diminishing returns. The more ethanol in the fuel, the more is used to attain the power produced by gasoline, the more ethanol you need to use to get the same mileage from an engine because of the power loss. I do remember when unleaded fuel came along I had to have stellite seats installed in all my older engines. It generally depends on how hard an engine is used as to how much wear it suffers. I also remember the lead in automotive paints used to allow a really beautifully smooooth paint jobs. Great summary!

I run pure gas when I can. You can find it allover in Florida. Could not find it at all living in NY. NYC area. Since then When my car and truck sits.... NOTHING evaporates. My gas level stays the same. Ethanol gas it just goes "Poof" in my tank Rusts steel gas tanks. Collects water. Crap. I have 1 year old Ethanol free gas now it still looks clear smells fine burns fine. I have 2 year old ethanol free fuel in another car. Same thing.

Ok Tony what did Amaco back in the day use to substitute the lead additive remember when they had lead free gas in the 40's 50' 60's and 70's . BTW I was a fleet mechcanic for over 30 years we had a 4000 plus car and truck fleet at the electrical utiliy company I worked at NOT one car or truck had valve seat problems when we switched to unleaded fuel in 1974 . I think because there was enough of a lead cusion on the valve seats already . to prevent the problem

My father who pulled water ski racers in the 60s and 70s (chrysler 392 hemi) HalRoy Hull by Harold Hanneman, Told me racers of that era didnt use Shell gas, They all used Chevron gas. Just my fathers opinion.

in the 1920s 8000 miles was the recommended overhaul by 20 -30-50 thousand miles the engines were wore out. but you could go to your local sears adn get one off the shelf reman. give up yours for core and you were driving that day.

In 1933 Chrysler began shrink fitting 6 steel rings into the exhaust port of their engines thus becoming the first company to do so in a production automobile. This was considered at the time as a watershed development.