TJweim

just got a 68 C3 and wondering about gasoline or additives for the leaded gas no longer available. What do I do if I cant find, probably cant, leaded gas?
I dont know if the valves have hardend seats or not. The guy I got it from put 100 or so miles on it in 20 years and he doesnt know.

Easy Mike

You'll be okay with unleaded fuel.

HeadsU.P.

Another old BS tale. Have yet to see damaged valveseats from unleaded gas. But the sale of the snake-oil, LEAD substitute in a bottle continues.

Dynra Rockets

I have seen sunken values where I attributed it to prolonged use (Daily driver) of unleaded. If you drive sparingly then I would not worry about it.

Dusky

Aren't the exhaust seats of a post 72' head induction hardend anyway?

F4Gary

I think it's 71 and on. But he bought a 68.
As I understand it, you don't have to worry about hardened valve seats unless you are loading up the engine a lot, like towing, or at a constant high rpm like in a boat or airplane.

Rodnok1

I'd run premium gas and gas with the least ethanol possible myself and not worry about additives unless you're going to beat the thing constantly.

HeadsU.P.

Neither octane nor ethanol have anything to do with the myth of protecting the old valveseats. And the more ethanol the higher the octane. Ethanol in itself is 113 octane.

drwet

Without lead the valve seats will slowly erode. That's why they started installing hardened seats and valve rotators when they took the lead out of our fuel. With that said, you may be all right if you don't drive the car much, or very hard. With my '66 I used Red Line Lead Substitute. Cheap insurance.

HeadsU.P.

Thats the myth all right. Thousands of pre unlead cars still out there running with millions of miles and no valveseat issues. H-m-m-m-m-m-m. And how many decades ago was lead removed?

694speed350

It may be but it takes twice as much of it versus gasoline.

bence13_33

I agree. I ran heads on my 468 that had closed chambers and they didn't have hardened valve seats....never had a problem. The only time I could potentially see an issue is in extreme cases where a lot of spring pressure is experienced on the seat. That could potentially cause issues eventually. I personally never had a problem.

drwet

Its not about spring pressures. Its really about heat. The exhaust valve gets hot enough that it will microscopically weld to the seat and pluck off a small amount of the seat every time it opens. Eventually this will erode the seat. That's why GM started installing hardened seats and exhaust valve rotators. Apparently rotating the valve slightly each time it opens helps to mitigate the problem. Obviously lots of guys run on unleaded fuel without hardened seats and don't have a problem, but enough do that I wouldn't take the chance with numbers matching heads.

fishslayer143

Back in the late 60 s and 70s , Amoco sold SUPER PREMIUM Fuel at its stations.. it was a high grade premium, 95 Octane if I remember correctly, and it was UNLEADED.. ZERO LEAD.....We all ran that stuff in every car we owned .. many of them only knew WOT or off.. a couple with 11 and 12 :1 compression.. We never had a valve seat issue.. not one..

bashcraft

Valve recession happens when the engine is heavily loaded for long periods of time. I've seen it several times in older vehicles, once in a pickup truck that was used to pull a 10,000 lb trailer and twice in dump trucks.

My point is, unless you're pulling a heavy trailer with your vette, you don't need hardened seats, or lead additive.

HeadsU.P.

Yup. You can lead a horse to water, but you can't make 'em . . . . .