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As far as octane level, most pre-70s cars are low compression in comparison to modern motors, so even running on 89 octane fuel is fine. No need for premium, which is primarily needed for high performance modern (high compression) motors.
Well, my '69 Cadillac has a high compression ratio (10.5:1) and definitely needs premium fuel. So does my '66 Plymouth with 383-4 bbl (10.0:1).
Several 1970s Ford engines had compression ratios of 11.0:1 or higher...
1970 351C............. 11.4:1
1970 429CJ............ 11.3:1
1971 Boss 351........ 11.0:1
1971 429 CJ & SCJ.. 11.3:1
They do make and sell lead additives that you can buy at an auto parts store, for a vehicle that still has the old style valve train.
Back in the day before I had a license, I rode a moped that was built in 1978, that required leaded fuel. There was none sold at any station around where I lived so I had to buy lead additive to make up for it. I did however run the engine a few times w/o the additive w/o any noticeable side effects.
However I believe anymore, most older engines have had a rebuild or two and if so, hardened valve seats are usually installed.
I also knew of a guy that had a 1968 Chevy II with the original valve train on the inline 6 engine....I recall about 15 years ago, he had the head removed and sent to a machine shop to have hardened valve seats installed. I don't know if it was an end result of valve train issues or just updating the engine. He inherited the car from his grandmother who no longer drove.
Leaded gasoline does kill O2 sensors and catalytic converters, so think about that if you ever decide to use the stuff. "Why would I want to do that" you ask? Some gas stations and tracks with VP fuels sell 100 and 110 octane, both I believe have lead. Guys like me that run turbocharged engines that are prone to detonation from running a lot of boost often put this stuff in our tanks to keep detonation at bay. Detonation = killer of engines. Plus having fuel injection = an ECM = an O2 sensor. So either way it's risky, but an O2 sensor is far easier to buy and replace than head gaskets or worse, a complete engine.
Also on the oil issue...yes zinc has been reduced since roller camshafts don't really need the stuff to survive, plus i believe it's also been found to be a pollutant in the exhaust. For us flat tappet guys that spells trouble. For several years up until a few years ago, many hot rodders building their engines would experience a wiped camshaft lobe. There's probably other issues that caused it but the lack of zinc I think was the biggest one. There's nothing worse than a freshly built engine that loses a lobe on break in only to have to be torn down and rebuilt all over again.
Well, my '69 Cadillac has a high compression ratio (10.5:1) and definitely needs premium fuel. So does my '66 Plymouth with 383-4 bbl (10.0:1).
Several 1970s Ford engines had compression ratios of 11.0:1 or higher...
1970 351C............. 11.4:1
1970 429CJ............ 11.3:1
1971 Boss 351........ 11.0:1
1971 429 CJ & SCJ.. 11.3:1
Yes and one will usually opt for the high compression rout when doing an engine rebuild on these old cars to tweak as much performance as possible (i.e. flat top pistons and aftermarket heads), so it is very relevant for "non stock" older cars.
Mine is 10.5 and I even then I bump back the timing a bit from the max, use premium fuel, have an additional timing dial back knob installed near the dashboard, and have opted for a gallon or two of aviation fuel and the home made mixes (gas and toulene) when I wanted to max the timing and go down the dragstrip. Otherwise it does OK with premium fuel.
One note to readers - don't buy those octane boosters you buy at the parts stores. They only bump up octane a fraction of a point and are otherwise worthless.
Another thing I forgot to mention that pertains to this topic....some with those older higher c.r. engines that want to keep them looking original will sometimes swap out the OG head gaskets with thicker ones so it will lower the c.r. to run on today's pump fuel.
back when lead was first eliminated from gasoline there was a real concern with older engines running into problems with valve recession, these days however a lubricant has been added to gasoline to prevent valve recession. another thing you can do when rebuild time rolls around is to install stainless steel valves. competition products has an inexpensive line that works quite nicely, and they are less expensive than adding hardened seats.
in regards to the lack of zddp in newer oils, an inexpensive way to go for older engines with flat tappet cams is to add a can of stp blue, or stp red to the oil at each oil change. for most engines the stp blue will do nicely, but if you are running a high performance cam with high spring pressure, then run the stp red.
Wow, so many options, but I guess that's better than none. Thanks for all the good information everyone, I'm sure it'll come handy the next time I see a 1960s muscle car and get an urge to restore it, without having to worry about the use of unleaded gasoline.
It's been a while since I've seen gasoline with an octane rating higher than 95, the highest we can get now, at least here in Arizona is 91.
I recently acquired a 1959 Dodge Military 3/4 ton weapons carrier truck. I was concered about the fuel to use but after reading the reaponses on this site I was relieved to find I can use regular unleaded gasoline. Thanks guys
Anybody remember when the first "Unleaded Fuel Only" cars came out?
Gas stations at the time still sold leaded and unleaded gas. Unleaded cost a bit more, so people would either punch out the restrictor piece in the filler neck or use these little plastic adaptors so the leaded nozzle (which was bigger) would fit into the smaller hole in the filler neck.
I bet a lot of people messed up their catalytic converters trying to save a few cents.
Well Joseph, you still have a problem. The info in this thread is old. The organic additives that allowed our unleaded gas to be used in leaded gas engines is no longer used. Our EPA has declared it to be a cancer causing agent and it's no longer in the gas. What you need to find and there are several out there, is a fuel additive that has tetraethyl lead in the formula. A small bottle goes a long way and makes usually at least a full tank of gas. Normally these additives are not expensive- about 5 bucks a tank of 20 gallons. I use one made by VP Racing fuels but I don't know if it's available on the open market anymore. It called C5. I have several of the old FE engines that need it to keep the valves from eating the valve seats out. You can put in steelite seats and cure the issue or run the additive. I'd also look for isobutanol gasoline, if you live close to a marina. You can get the required octane that the engine was designed to use there. The "regular" octane has a 100 rating. Otherwise, performance, if you can call it that in the little flathead engine, will suffer.
Anybody remember when the first "Unleaded Fuel Only" cars came out?
Unleaded fuel only? I think that started in 1975. My 1976 Cadillac requires unleaded fuel only.
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