Lead additive question

[Jmac05]

Anybody use a lead additive? Can we? What good/bad does it do?

[GMC1967]

I used to use the additive before i had my engine rebuilt, and had them put in hardened valves and seats. You should use the additive on any american engine before 1973? Not sure about that, I know that in 1973 Catalitic converters became mandatory and the lead additive would clog these. And somewhere between 1969 and 1972 they started hardening the heads to burn unleaded fuel. So it definately won't hurt anything (unless for some weird reason you have cats or an oxygen sensor), and you should definatley use it if your engine doesn't have hardened valves and seats.

[Maximum Overdrive]

When they first discontinued leaded gas here a few years ago I had to use it but then the local refinery said they put some other type of thing in the fuel and people no longer needed to use lead additives.

[Longhorn Man]

Actually cats started in 75...but not like that really matters.
I would add it even if the oil companies say the fuel is good. Those greedy bastards will tell you what ever you wanna hear.

[GMC1967]

Not to be disagreeable but I have a 1973 oldsmobile delta88 with a factory cat on it. I've always known this to be the year it became madatory, because I know '72's didn't have them, and I don't see why GM would put those on there if the government didn't make them...

[Longhorn Man]

well crap.
I coulda sworn....
Oh well. Thanks.

[GMC1967]

No, big deal, I could still be wrong somehow, but I must say, I feel a little humbled trying to correct the mighty longhorn

[Longhorn Man]

LOL!
Look around...it happens quite a bit!
Thanks though...Your maikin me smile after a long hellish day.

[bobs409]

The '72 Chevelles went to unleaded gas but no cats. I would think the trucks and all other models would be the same.

I've heard that these additives are worthless anyway. I put a little Marvel mystery oil in with the gas once in a while on my 409. If you have an old engine that hasn't had any machine work done, it should have a build up of lead in it from years ago. (that's what I've been told anyway)

[toms68cst]

I seem to remember that pickups went to cats later than cars. Like around the mid-late 70's. Also the 72 truck brochure I have says; (I don't know what year truck you have jmac05)

"All Chevy light duty engines perform on no-lead lo-lead or regular fuel. They have induction-hardened valve seats for added durability using these fuels."

Of course back in those days "regular" fuel was leaded fuel.

[Michael A. K. G]

My '72 owner's manual says to use unleaded or low-lead gasoline in all C10-30 trucks, but you can use regular if that is all you can find (no cats).

It also says to use at least 91 octane!

[Jmac05]

That's all good, but what does it do? What difference is it to have it/not have it?

[71GMC_3/4T]

I once had a 74 Monte Carlo that was originally built for Calipornia. It didn't have the cat, had AIR pump, had the big filler neck for gas, but had a label that said you could run unleaded.
I'm like Longhorn, I could've swore they started unleaded in 75 for cars and light trucks. I also had a 75 1/2 ton Pickup that was unleaded only, with small filler, cat, AIR pump and the "unleaded fuel only" legend on the fuel guage. I know for a fact that 3/4 tons in that year were leaded regular burners, but I don't know when they made them go to unleaded.

Jmac, I just run the generic pump gas, no lead substitute. I figure some day I'll need a valve job. So I'll need it 10,000 miles sooner - no big deal... The lead substitute lubricates the valves for anal people who have the really old classics they don't ever want to rebuild. I'm looking forward to rebuilding mine some day. And I'll either go with new heads or have hardened seats and valves installed then. Until then, I can adjust the lifters to compensate for valve wear occasionally. Makes me look under the valve covers to make sure everything else is running like it should.

[dbenamati]

I ask an old time mechanic tonight on his thoughts on the leaded additive. He told me it doesnt hurt to use it but the damage that non leaded gas would do to an engine that was designed to use leaded gas would me minimal. The lead acts as the lubricant which everyone probably knows. What I didn't know is the lead doesn't go away. My 67 probably has lead on the valve seats from years ago and leaded gas. His opinoin"it only costs a buck or so, use it once and a while", it can't hurt. So I bought a bottle today and threw it in.

[mikep]

First off there is no lead in lead additive. There isnt even anything resembling lead. Thats a good thing. Tetraethyl Lead was a great valve lubricant and Octane enhancer but it is a nasty deadly poison that you wouldnt want to deal with even if it were available which it is not. Even Leaded gas when it was available until 1986 contained only a fraction of the lead (.5 grams per gallon compared to 3 grams per gallon of the old hi test ) that it contained back in the old ethyl gas days . If you were around back then and ever had to siphon gas you'll remember the taste of leaded gas . Yuck !

Its usually just a form of oil in the "lead substitutes" . You could throw in a few ounces of engine oil with every fill up and get the same effect. Its sort of the marvel mystery oil effect. Do it if it makes you feel better but its probably not going to make your engine do anything but build up nasty deposits on the backside of the exhaust valves and it will have a little blue smoke coming out the exhaust.Point is... when you get your valve job done ( or buy good modern heads ) dont skimp. Pay the extra $100 and get stellite seats ..

BTW ... On a related subject Octane booster is nothing but straight Toluene. I used to buy a 35 gallon drum at a time when my brother worked for BF Goodrich industrial chemical division . I ran a 12:1 compression big block Ford in my 70 Cougar and I'd mix 2 gallons in a tankfull of unleaded. Never detonated! The stuff cost me $32 for the 35 gallons.

Also . Occasionally when I have a car I want to race I'll make a run down to the local municipal airport in my area. Bremerton international where I am at. I bring a few 5 gallon cans and fill them up with 100 LL avgas. The 100 is the octane rating and the LL stands for low lead but its still got 1.5 grams per gallons of lead which aint to shabby. Last time I filled a few cans up was about 6 months ago and the stuff was going for $2.25 a gallon which if you figure you might throw 2 gallons in per tankfull for a little extra insurance and a litle extra octane would make sense . You could even run 87 octane unleaded and the avgas would pay for itself. Hell... I'm running down to the airport tomorrow now that I think about it.

[MJN]

I still fill up with lead additive gas at the pump here. Even with the new engine the knock went away and seems to have some more power. My dad always told me to run leaded gas with the old trucks and it wouldn't hurt it anyway. It may be a little more expensive but I'd rather run it than plain gas.

[dmnall]

Well the problem is if you have heads that have not had Hardened Steel Exhaust Valve Seats, then run the lead substitute. If you have newer heads like Vortec, or had new exhaust seats in your heads, I say save the money for more gas.. The problem that can/will happen if you do not run lead substitute in heads that does not have Hardened Steel Exhaust Seats, is that you risk of your exhaust seat breaking down and then you would lose compression!!