i just bought a nice 68 conv. with a 327 3speed auto. and i was wondering what type of gasoline to use in it. the owners manual tells me to use the gas "from any gas station" or something... but that was in 68... not now. i talked to a guy who has a 69 corvette and told me to add a lead additive to my gas or else the engine will stall up.... (when he bought the car the engine was froze solid..... said that the previous owner never put lead in the gas and that's what happened) so i was wondering should i use a lead additive to my gasoline or just use unleaded.... finding a lead additive wouldn't be a problem for me since i live in a farming community, most tractors and such need the lead anyway... please reply with what u think would be best.... thank you

I have a '68 BB that runs just fine on 93 octane unleaded. As long as your vehicle is timed right, it'll run with no problems.

The Internet is full of papers on this subject, just do a search. The real issue with older motors is that they were designed with the intent that lead would provide protection for the valve seats. That's why Chevrolet (and others) added hardened valve seats to the heads in about '71. If the valves are sinking into the heads, you won't feel it until it's too late. Depending on which paper you choose to believe, this can take anywhere from 10,000 to 100,000 miles to happen. For the small cost and effort involved and the minimal miles that I drive, I feel better using an additive.

Maybe it's better to be safe than sorry. Even if it is a daily driver, it wouldn' t hurt to put in the lead additive. Shouldn't cost that much..


|QUOTE|JSB69 said: The Internet is full of papers on this subject, just do a search. The real issue with older motors is that they were designed with the intent that lead would provide protection for the valve seats. That's why Chevrolet (and others) added hardened valve seats to the heads in about '71. If the valves are sinking into the heads, you won't feel it until it's too late. Depending on which paper you choose to believe, this can take anywhere from 10,000 to 100,000 miles to happen. For the small cost and effort involved and the minimal miles that I drive, I feel better using an additive.|/QUOTE|

Hey Everyone!


Does anyone know what lead does in our engines? I'm assuming that putting leaded gasoline in an engine made for unleaded is going to cause headaches... what happens if you put in unleaded gasoline in an engine made for leaded gas?

Just curious..

Imran
74 Convt

From what I understand, the lead in gasoline acts as a lubricant ( that statement does not mean it is correct ). If the valve seats are 'Hardened" you do not need the lead. K Page, you should try to find the last owner and ask if the heads were ever "done". Then you will know for sure if you need the lead additive.

Glenn,

If the lead acts as a lubricant, shouldn't we all be putting lead in our gasoline? I mean, as long as it doesn't hurt anything, lubrication should be a good thing for the engine.

Imran
74 Convt

The guy with the '69 Vette is a moron, K. The short history of tetraethyl lead (TEL) in gasoline is...well short. It wasn't added until the early 50s and that was just as a cheap and effective way to increase the fuel's octane rating to suit the advent of the "modern" high-compression engine. The lead was also a beneficial lubricant and cushion for the exhaust valve seat with the "modern" engine's higher combustion temperature. The downside of TEL is that it is very corrosive to cast iron and causes severe wear in the cylinder's bore, the lifter bores, and the exhaust system. The petro-chemists added a chemical package to neutralize the corrosive effects of TEL, but it could only go so far and is why an engine in the "old" days was pretty worn out once it was over around 80k miles or so and you had to replace your exhaust about every other tire replacement.

Now, with introduction of low-lead and no-lead fuels in the early 70s, manufacturers had to provide an engineered solution to the lack of lead. Almost everyone induction hardned the exhaust seat and changed the alloy in the exhaust valve for a higher nickle content. This solved the longevity issue. So, the only "design" component in an engine designed for unleaded or leaded fuel is the exhaust seat and valve. Nothing else is different because nothing else is affected. If you wanted to modify your engine to be an engine designed for unleaded fuel, you would only have to install a stellite valve seat and possibly new stainless exhaust valve. Or, you could play the odds and leave everything be and find out just how many miles your engine will go before the exhaust valve sinks. The worst that can happen here is that you end up installing the seat.

But of greater concern is the octane rating. Your engine will be destroyed by detonation long before you see any effects caused by the lack of lead. Take care of your octane first. If you want to add a lead substitute, then go ahead. It may help some and absolutely won't hurt anything.

|QUOTE|Gerry Proctor said: The guy with the '69 Vette is a moron, K. The short history of tetraethyl lead (TEL) in gasoline is...well short. It wasn't added until the early 50s and that was just as a cheap and effective way to increase the fuel's octane rating to suit the advent of the "modern" high-compression engine. The lead was also a beneficial lubricant and cushion for the exhaust valve seat with the "modern" engine's higher combustion temperature. The downside of TEL is that it is very corrosive to cast iron and causes severe wear in the cylinder's bore, the lifter bores, and the exhaust system. The petro-chemists added a chemical package to neutralize the corrosive effects of TEL, but it could only go so far and is why an engine in the "old" days was pretty worn out once it was over around 80k miles or so and you had to replace your exhaust about every other tire replacement.

Now, with introduction of low-lead and no-lead fuels in the early 70s, manufacturers had to provide an engineered solution to the lack of lead. Almost everyone induction hardned the exhaust seat and changed the alloy in the exhaust valve for a higher nickle content. This solved the longevity issue. So, the only "design" component in an engine designed for unleaded or leaded fuel is the exhaust seat and valve. Nothing else is different because nothing else is affected. If you wanted to modify your engine to be an engine designed for unleaded fuel, you would only have to install a stellite valve seat and possibly new stainless exhaust valve. Or, you could play the odds and leave everything be and find out just how many miles your engine will go before the exhaust valve sinks. The worst that can happen here is that you end up installing the seat.

But of greater concern is the octane rating. Your engine will be destroyed by detonation long before you see any effects caused by the lack of lead. Take care of your octane first. If you want to add a lead substitute, then go ahead. It may help some and absolutely won't hurt anything.|/QUOTE|

I take it someone's done a bit of research on this topic. Thanks a lot!
You said that it had a corrosive effect on cast iron, so wouldn't that still remain a problem going through your engine? Also, I'm sure the environmental aspects of using lead in gasoline can't be all that great. I'd rather have less lubrication and still have functional lungs when I'm older :)
Just my two pennies..

Imran
74 Convt

Gerry
Did you say that the lead substitudes are different material as the actual lead used in early fuels ?
Over here in Europe, we can get 98 Octane unleaded fuel and some stations still sell 98 Octane fuel with lead substitude.
The little bottles we also can buy actually say lead substitude, not lead additive.
Is this different and better, say non corrosive and are this meant to lubricate the exhaust valve seat or for detonation , speak Octane increase ( which we don't need with 98 Octane fuel ) ?
Now I'm a bit lost on this.
Thanks for clearifying. Gunther



|UPDATED|6/19/2002 5:59:11 PM|/UPDATED|