What is the lead additive I need to add to my gas for proper engine operation and break in? Where do you get it and how often do you add it?

Thank you!

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1972 Datsun 240z #88178

you don't need it

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

You don't need it anymore.

Lead additives were needed as anti-knock compounds for hi-compression (10:1 or above) engines, and for 'soft' valve seats before they all became hardened.

It used to come in pump gasoline, back when it was required. But the EPA (now the DEP) discovered it was polluting the air with some pretty dangerous fumes, so it has been deleted from pump gasoline here in the States.

In order to avoid valve seat damage (since our gasoline became unleaded), manufacturers began building cylinder heads with 'tough' valve seats which don't require lead. To avoid pinging or detonation in hi compression engines, other additives have been mixed into pump gasoline, and engines have been designed with generally lower compression ratios. Your CR should be *somewhere* around 8.8:1, if memory serves.

If you have a racing engine (BIG compression ratio; maybe 12:1), today's racing fuel will provide all the anti-knock compounds you need. All you have to do is pay about $8/gal for it.

Bryan Little's great website, www.DatsunZGarage.com has an excellent explanatory section about automotive fuels.

Frank

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1970 240Z

Beautiful. Thank you both. Now I can stop thinking that i'm hurting my engine!

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1972 Datsun 240z #88178

Actually.....not to make you paranoid, but since you have a 1972 with a pre-1977 Datsun (E31, E88, N42) head, then you have a head designed for leaded gas...and softer brass seats that tend to recede without it. So if you're running the original seats its a good idea to put an occasional bottle of lead additive in your gas.....sold for classic cars at the auto store.

Acecdote: When I was in London in 1997 or 2000 they had billboard ads for shops that would pull your head and replace your car's valve seat with steel ones...because they recently had dropped leaded fuel. Funny that there wasn't the push here in the states for that.

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Bryan Little
Datsunzgarage.com

1970 240Z - enhanced F54 L28 w/P90, Weber DCOEs, 4:11 R200, Nissan T5 5-speed

Biut I thought Datsun made their valve seats steel in 1971?

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1970 240Z

There were softer seats in the early z-cars but they wear pretty slowly if you keep valve lash adjusted properly. By "pretty slowly", I mean well beyond 150k miles. The assertion that using leaded fuel will make them last even longer is pretty generally recognized as unsupportable. The lead additives in gasoline were not added to enhance engine longevity but rather to cheaply boost octane levels, and leaded gasoline was discontinued both because of its pollution and because it fouled catalytic converters. There are even older engine designs which NEED leaded fuel to preserve their valve seats but the l-series is pretty tough as it is, and the minimal improvement in longevity that you MIGHT experience is just not worth the hassle. The time to worry about beaten-in valves is when you can no longer adjust valve lash to proper specs or when you have the head off anyhow.

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

My engine was built with hardened seats so I should be good to go. We will see. Thanks for weighing in!

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1972 Datsun 240z #88178