Leaded fuel question...

[Patrick T.]

I have a stock '67 L-79, 327/350 hp motor. I talked to a previous owner who told me he had the entire engine rebuilt to stock specs while he was doing a cosmetic restoration...new pistons, cam, valves, everything.

The other day, I bought 5 gallons of CAM 2 110 octane leaded racing fuel for it, at $6 a gallon. I mixed it with 5 gallons of 92 non leaded fuel with 10% ethanol added. The car runs better but I'm still evaluating that. I could hear the engine smiling as it slurped up that leaded gas though.

Anyway, I heard long ago that lead was good for these 40+ year old engines back in the day because the lead left a deposit on the exhaust valves and seats, thus protecting the valves and seats from the intense heat.

Yeah, this sounds crazy but I'm just curious... how long did it take the engine, running on leaded fuel, to leave a decent deposit of lead on the seats? A month, a year, a decade? As I stated above, all these engine internals only have a few thousand miles on them. Any guesses? Thanks, PT

[Bill I.]

Re: Leaded fuel question...

Pat, I'm not sure there is a real answer to that, I would think at least a year. I do not run any additives in my L79, and no problem. Just use 93 octane. Bill

[William C.]

Re: Leaded fuel question...

You might check with the previous owner to see if he installed hardened exhaust valve seats. If so, you can run unleaded without a problem.

[Joe L.]

Re: Leaded fuel question...

I have a stock '67 L-79, 327/350 hp motor. I talked to a previous owner who told me he had the entire engine rebuilt to stock specs while he was doing a cosmetic restoration...new pistons, cam, valves, everything.

The other day, I bought 5 gallons of CAM 2 110 octane leaded racing fuel for it, at $6 a gallon. I mixed it with 5 gallons of 92 non leaded fuel with 10% ethanol added. The car runs better but I'm still evaluating that. I could hear the engine smiling as it slurped up that leaded gas though.

Anyway, I heard long ago that lead was good for these 40+ year old engines back in the day because the lead left a deposit on the exhaust valves and seats, thus protecting the valves and seats from the intense heat.

Yeah, this sounds crazy but I'm just curious... how long did it take the engine, running on leaded fuel, to leave a decent deposit of lead on the seats? A month, a year, a decade? As I stated above, all these engine internals only have a few thousand miles on them. Any guesses? Thanks, PT

Patrick------

I think you wasted your money. If your car doesn't "ping" with 93 octane gas, the extra octane is not going to do a thing for it.

As far as the lead goes, I doubt you'll live long enough to experience an exhaust valve seat problem caused by unleaded gas. The guy that gets the car after you're gone probably won't have any problem before he goes, too.

[Patrick T.]

Re: Leaded fuel question...

Ok, thanks for your replies. No, there were no hardened valve seats installed. PT

[Joe L.]

Re: Leaded fuel question...

Ok, thanks for your replies. No, there were no hardened valve seats installed. PT

Patrick------


Hardened or not, you won't have any problem with the exhaust valve seats using unleaded gas.

Engines that have problems with exhaust seats are those that run under heavy load for extended periods of time. I've spoken with fleet managers that dealt with industrial duty engines which are run for extended period under heavy load. Every one told me that they NEVER had a problems with exhaust seat recission on these engines even using unleaded fuel.

[Clem Z.]

Re: Leaded fuel question...

according to GM 5000 miles of driving with leaded fuel will put enough lead on the exhaust valves to last the life of the engine

[Paul H.]

Re: Leaded fuel question...

I've been driving my 65 L79 for many years on unleaded 93 Octane with no additives. No problems. No hardened valve seats. In fact, the plugs last alot longer than they did in the old, leaded gas days. Valve recession caused by using unleaded gas is a long perpetuated myth IMO. All of my old Corvettes have run fine for years on unleaded fuel. If your L79 pings or runs poorly on unleaded, premium pump gas, I would be looking at my timing map, carb, vacuum advance and tuneup specs.

[Jack H.]

Re: Leaded fuel question...

This was answered a LONG time ago when no-lead gas first made its debut in the US. BTW, the UK only stopped selling leaded gasoline at the pumps about 6-years ago and they went through the same 'Chicken Little' Q&A concerns we did back in the '70s...

The 'answer' came from a Daimler Benz white paper on the subject. The issue was whether or not the lack of lead in our US fuel would either void the warranty or decrease the engine life of Benz cars/trucks produced prior to the introduction of unleaded fuel.

The white paper concluded two primary things:

(1) Once a given engine had logged 5,000 miles on it with leaded fuel, it'd absorbed all the lead it'd ever need to thwart valve recission.

(2) On the issue of lead needed for octane boost, IF the no-lead fuel had a sufficiently high (correct for the engine application) octane rating, any/all additives used to boost octane were essentially a waste of money (throwing $$$ out your tail pipes).

[Clem Z.]

Re: Leaded fuel question...

This was answered a LONG time ago when no-lead gas first made its debut in the US. BTW, the UK only stopped selling leaded gasoline at the pumps about 6-years ago and they went through the same 'Chicken Little' Q&A concerns we did back in the '70s...

The 'answer' came from a Daimler Benz white paper on the subject. The issue was whether or not the lack of lead in our US fuel would either void the warranty or decrease the engine life of Benz cars/trucks produced prior to the introduction of unleaded fuel.

The white paper concluded two primary things:

(1) Once a given engine had logged 5,000 miles on it with leaded fuel, it'd absorbed all the lead it'd ever need to thwart valve recission.

(2) On the issue of lead needed for octane boost, IF the no-lead fuel had a sufficiently high (correct for the engine application) octane rating, any/all additives used to boost octane were essentially a waste of money (throwing $$$ out your tail pipes).

looks like GM and benz did the same tests.
according to GM 5000 miles of driving with leaded fuel will put enough lead on the exhaust valves to last the life of the engine. i removed the cat converter from my 88 silverado when it was new so i could run leaded fuel till it was no longer available and 22 years later the trucks runs great.
__________________

[Joe L.]

Re: Leaded fuel question...

I've been driving my 65 L79 for many years on unleaded 93 Octane with no additives. No problems. No hardened valve seats. In fact, the plugs last alot longer than they did in the old, leaded gas days. Valve recession caused by using unleaded gas is a long perpetuated myth IMO. All of my old Corvettes have run fine for years on unleaded fuel. If your L79 pings or runs poorly on unleaded, premium pump gas, I would be looking at my timing map, carb, vacuum advance and tuneup specs.

Paul------


The late John Lingenfelter once said that the best thing that ever happened for performance was unleaded fuel. I've never forgotten that and I agree with him.

[Clem Z.]

Re: Leaded fuel question...

Paul------


The late John Lingenfelter once said that the best thing that ever happened for performance was unleaded fuel. I've never forgotten that and I agree with him.

for real hi compression race engine you still need leaded fuel as unleaded race fuel is only up to 100 octane. it is also very light sensitive and must be stored carefully.

[Patrick T.]

Re: Leaded fuel question...

according to GM 5000 miles of driving with leaded fuel will put enough lead on the exhaust valves to last the life of the engine

Thanks Clem, that answers my original question. PT

[Paul D.]

Re: Leaded fuel question...

My '67 L79 runs fine on Exxon 93. No ping on a freshly built motor with the stock pistons,stock timing. Passed PV on it also....Paul..

[William C.]

Re: Leaded fuel question...

My '67 L79 runs fine on Exxon 93. No ping on a freshly built motor with the stock pistons,stock timing. Passed PV on it also....Paul..

Paul,
It always ran well for me. I would bet that is one of the most original cars
around. Send me some pics of the car.
Thanks,
Bill (2nd owner)
whc67@verizon.net