I just bought an original 1950 Pontiac Silver Streak with the inline flat head 8 cylinder. It‘s an old 6 volt car, and it runs great! I‘ve never owned something this old before and I was wondering if I should run a lead additive and what octane gas I should run? There‘s 87 octane in it now, but no lead either. I don‘t think the head has been off, nor have the valve seats been hardened. What do you think???
Honestly, this is a question for a very experienced cylinder head specialist. Some older engines had problems with valve recession after lead was removed; others had no problem at all. Back in the 90s a mechanic had a radio show Saturday mornings in Phoenix and the subject of unleaded gasoline came up. He related that in a bull session with other mechanics in the area it came out that in their over 100 years combined experience they had never seen an engine with valve recession from unleaded gas. I suspect in England the conversation would have been different - a lot of British Leyland and British Ford engines had trouble if pushed hard. But as Jim Walker posts in the source, Using additives just about equates with me a 72 year old widower putting on a condom every day - just in case! I don't know when GM started using hydraulic lifters but if your has solid lifters you should check valve lash periodically in any case. Valve recession shows up as decreasing lash until finally the valve has no lash at all and burns.
Lead additive is snake oil. It was used as an anti knock, and for lubricity. When lead was done away with, other compounds were introduced to replace it. I have been driving a '57 Chevy for 21 years now, have never used lead additive, and it runs perfect. The valves seats have not been replaced.I use 89 octane. This is not the only old engine I have, some dating back to 1910, and none have had lead additive, ever. I have never seen any proof that it is necessary. My '66 Mustang is lead free as well.
