1970 Lead fuel additive
Burning Brakes
Joined: Nov 2012
Posts: 788
Likes: 100
From: Indianapolis IN
Lead had the side effect of cushioning valve seats, but no effect upon valve seals. The short answer is NO , lead isn't needed for any reason if this engine is being used in a passenger car.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,074
Likes: 4,208
From: US-PNW
My engine machinist told me that the original use of leaded gasoline for my '72 had changed the metal's seat chemistry/qualities to provide permanent protection even after the use of unleaded fuels was the only choice. For this reason he recommended against changing to hardened valve seats unless absolutely necessary where cutting deep into the seat would remove too much of this protective layer. As I recall, he merely honed the seat angles and changed the guides to bronze.
I don't know if his knowledge, or my relating of the advice, is accurate but it was a conservative approach and obviously not in his financial interest to recommend this route.
I don't know if his knowledge, or my relating of the advice, is accurate but it was a conservative approach and obviously not in his financial interest to recommend this route.
Tech Contributor
Joined: Aug 1999
Posts: 14,377
Likes: 6,377
From: At my Bar drinking and wrenching in Lafayette Colorado
As Tim correctly stated above, the answer is "no." The SAE did a lot of testing in the late 60's and early 70's when the industry was aware of the upcoming ban on lead in auto fuel. That testing showed that there is no harmful effect on valves and valve seats in engines (without hardened valve seats) running on unleaded fuel in normal passenger car applications. Engines running in extreme continuous load applications at elevated exhaust gas temperatures (defined as running at wide open throttle for more than 15 minutes continuously at a time) saw an accelerated deterioration of the valve seats. For this reason, the US automakers started building engines with induction-hardened valve seats starting in the 1971 model year, as correctly noted by Owen above. For your 1970, as long as you're not pulling a fully loaded horse trailer up a Rocky Mountain pass at wide open throttle for 30 minutes at a time, you will have no problem.
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