Unleaded Gas? Is it full of hot air?

I’m currently restoring a 1964 Ford Falcon and installing a 1965 200 C.I 6 cylinder engine. This is my question do I really need to use lead additive? Everyone I’ve asked has had a different answer. From “no, it runs fine on regular unleaded” to “Just use 89 octane” To “use a small bit of jet fuel mixed in.”

Does anyone KNOW if lead additives are needed on these older engines, and if so, how do you tell when an engine falls into that category, is there a year cut off?

My understanding of it is that the lead in the gasoline helps to protect the valve seats. Without the lead or some kind of an additive they will wear more quickly.

I once had a 72 Dodge motorhome, and at another time a '64 Ford F-100. I was always told that the additive will make a big difference if the engine sees a lot of heavy duty use (e.g. towing, mountains, other hard driving). But that otherwise the effects would be minimal. I tended to use it in the motorhome but not in the truck which saw only light use. I never put enough miles on either one to notice any difference or problems.

If the motor you are dropping in was just rebuilt, then it is unlikely that you would need any additives since the valve seats will be able to hold up without the lead.

One thing for certain is you will get a variety of opinions on this subject.

Unleaded gas became widespread in 1975 when catalytic converters showed up on cars. Engines built in 1975 and forward had ‘hardened’ valves and seats to accommodate unleaded fuel.

Being a soft metal, the lead in the leaded-fuel acted as a cushion to the valves when they closed.

Many of us remember pre-1975 cars experiencing burned valves when they used unleaded gas for prolonged periods. But you’ll also see numerous others who say they’ve run unleaded in pre-1975 cars without any problems.

Gonna be hard to find someone with the expertise to know just how tolerant the valves and seats in that particular head will be to unleaded gas.

If you plan to use it just for a hobby car on weekend drives, I would not worry about it.

If you plan to use it for a daily driver and drive it another 100k miles, then it would be prudent to either use lead or a lead substitute, or if you are doing any head work before assembling the car, look into cutting out the valve seats and pressing in updated valve seats. We did that to a lot of engines back in the 80s. At that time we noticed that some engines seemed to tolerate unleaded gas just fine, while others burned valves or hammered down their valve seats.

I don’t know if updated press-in valve seats are still available. The updated valve seat tolerates unleaded gas, but does not transfer heat as well to the head, so it is not a perfect solution.

Engines of that era were often modified to run on propane in commercial use and suffered no ill effects. And obviously, there was no lead in that fuel.

During this same time period, Amoco (Standard Oil) sold unleaded 100 octane premium fuel (clear as water) and high performance engines LOVED it with no valve problems.

Your Ford Six will RUN FOREVER on 87 octane unleaded fuel with no problems at all. Now the old “leaded” regular was usually rated at 90 octane, so if you notice a little spark knock or “ping” you might need to feed your Falcon a little more octane but it does not care about lead. Tetra-ethyl lead has no valve “lubricating” properties at all. That’s urban legend stuff…

The 1969 Dodge I drove in the early 1990s ran just fine on unleaded gas. You should try it. If you don’t like the way it runs, buy some lead substitute, not lead additive. Lead substitute will do the same thing without poisoning the air.

You will certainly have no problem if your 200 already has the hardened seats, many old engines have had this done already, anyone you could ask? Probably won’t hurt even if it doesn’t, if this just a weekend driver. I don’t understand the ‘use a small bit of jet fuel’, that’s similar to diesel or kerosene. Had they said ‘use some aviation gas’, that might make more sense, some has lead, but there’s no legal wat to put it in your car.

Your Falcon was made before the switch to unleaded. Some cars were given hardened valve parts prior to the switch, many others had little or no problem with the switch. I had a 1965 Sunbeam Imp and it never had a problem, neither did my 1970 VW, both of which had many miles post leaded fuel.

I suspect the Falcon was also OK without lead, but it may not have been.

The worse that will happen is your valves and valve seats may need replacement. I would guess that the odds are very high that the engine you are looking at was designed with hardened valves, or it has had them added over the years.

Note: Octane is not really part of the game. Lead was used to increase octane and after lead was removed, they just used other additives to do the same thing.

I don’t know about the Sunbeam, but the VW had an aluminum engine and so the lead replacing worn iron in the cylinder head wouldn’t apply. My 1964 Buick oddly enough has an engine with aluminum heads and so it’s still ticking along just fine on unleaded gas without, as far as I know, anything in the way of modifications.

But, to the OP, after '75 installing hardened valve seats became a standard part of any valve train work or anything that involved pulling the heads. Because such work was needed fairly frequently on older cars, unless this Falcon has been sitting in a barn since before '75, it is highly likely that it has the hardened seats installed and no additives are required.

Since I couldn’t see a way to edit the original post to add this info I’m replying here. I have acquired 2 engines one, is out of a 64 falcon that appears to have either 159K or 259K miles on it, with a head that was rebuilt sometime around the time it was taken off the road (Circa 1995) I have a second engine that supposedly has only 60K on it, that was taken out of a mustang and has been sitting since that car was wrecked. (80’s) So, the one might have had the seats replaced already. If not, from what I’ve read, I plan on replacing them. Thanks for the help.

Aluminum heads have hard seats installed O.E. And yes, American (AMOCO) sold 100 octane unleaded in the 60s and bragged about it, and charge a 5c/gal premium for it. Cadillacs specified using the AMOCO.

I rememmber that a well tuned and maintained engine would “chaulk” the tail pipe when using leaded fuel.

Stay away from ethanol in the gas if at all possible.

You have to remember, you’re running a fuel system that was never designed to run any kind alcohol. And ethanol can take out things like gaskets/seals in the carb to causing the fuel pump diaphram to rupture.

See if there’s a hot rod/street car club in your area, and if they provide a list of gas stations that provide non-oxygenated gas. Such as this site http://www.msra.com/


I suppose I could be wrong, but I believe aluminum engines have inserts and sleeves that are steel.

All my motor-head friends in the 1960s swore that running only Amoco unleaded in an engine would make it last forever. This “need” for lead was only in reaction to the government forcing everyone to use unleaded. In other words, it’s mostly bunk. People don’t like having the government tell them what to do and they come up with all sorts of reasons why they shouldn’t be forced to do whatever.

If it were my engine I would not worry one bit about it.